12v DC in Plane Inglish

I see a lot of very basic questions in forums about 12v DC electronics and often see them replied to with some very complex answers.

12v DC electronics is actually a very precise science and it's really quite easy to understand once armed with some basic information. There's nothing stupid about not understanding it. Most of us go through life never having to think about it. It's only when we're thrust into (or maybe gently led) into the world of off grid living that we have to understand a few basic rules.

Please note: information provided here is also applicable to bricks and mortar dwellings. You do not need to be a licensed tradesperson to undertake 12v installations. If necessary, cabling for 12v DC systems can run freely through dwellings. Basic 12v DC systems can dramatically cut home electricity bills. It doesn't matter how many thousands of dollars you are told emphatically that you must spend, by solar power contractors; you CAN cut out the middle operator and install very inexpensive systems yourself. 
This guide does not offer schematics as setups can differ greatly. Do not hesitate to contact me for further advice.
Renewable energy is vital to our future, but already it has become an industry rife with operators who provide misinformation for the purpose of profit. Much of that misinformation pertains to the validity of more basic systems. Electrons are electrons - it doesn't matter how you convert them from photons, just as long as you benefit. 

Some 12v stuff

Ohms / Power Law Basics - It's really simple. Honestly!

The main things we need to concern ourselves with are:
1. Power - Measured in Watts and abbreviated as P. This is the amount of work that an appliance or light globe does.
2. Current - Measured in Amps and abbreviated as I. This is the amount of electricity that's drawn from your battery.
3. Voltage - Measured in volts (surprise, surprise) and abbreviated as E. This is the potential difference between two points, more simply described as pressure, like the water flow in a hose.

P and I are very variable for the purpose of calculations. V doesn't vary much in a DC circuit. There are variations based on a batteries charge or depth of discharge (DoD), but it's reasonably negligible, so we use 12v as the basis for our calculations. There is an exception to this rule that I personally apply when doing  calculations involving inverters, but that will be explained in due course.

Some caravan RVs use 24v systems. They aren't as common as they are in large commercial vehicles, but the same rules apply, substituting 12 with 24.

The most important equation that we can remember is:

P / V = I

In plain English: Power in Watts, divided by voltage in volts, equals Current in amps.

It's important to be aware of how much current is being drawn, as that tells you how much you have left in your battery.

Example: 10 watt LED globe / 12v DC supply = 0.833 Amp current

Power is important for the purpose of calculating current. It's also important to know how much power  devices consume, if you are using an inverter or generator. If the appliance consumes more power than is provided by a source of electricity from an inverter or generator, they just won't work.

If you have a hair drier that produces 1,300 Watts, plugged in via a 1 KVA (1,000 Watt) generator, the generator will cut out. The same goes for inverters. 

Appliances that heat or cool via compression (air conditioners) consume a lot of power. That's why items such as electric heaters, hair driers, electric kettles etc, are very impractical in terms of most small off grid 12v DC power set ups. 

Heating appliances are too powerful for small, practical inverters and generators, whilst large inverters / generators draw far too much current to be practical . In the case of inverters, they run batteries down quickly. In the case of larger generators, their power capacity is inversely proportional to their size, weight, noise level, fuel consumption and cost. 

Batteries

Types of batteries have been discussed in a previous post: The Best Things In Life Are Free Camps.

The vast majority of house batteries are AGM (absorbed glass mat) deep cycle batteries, so I'm basing information on AGM batteries. 

Deep cycle batteries are designed to deliver a steady current over a period of time and discharge / recharge slowly. These differ from cranking (car batteries) that are designed to deliver a large current in a short burst in order to start a car. They are recharged quickly by means of the car's alternator.

Lithium batteries are becoming increasingly popular for many reasons. The downside is the cost. They're one of my many pet hates for political reasons. More later. 

For the purpose of deep cycle house batteries, capacity measurements are generally rated in "Amp hours (Ah)." 

This is the measurement of how much a battery holds, based on how many hours it can supply a continuous current of 1 amp for. 

If a 100Ah battery is under a load of 1 Amp, technically it will supply power for 100 hours before it is totally discharged. If the combined load of your lights and appliances is 10 Amps (that's very high by the way), a 100 Ah battery will fully discharge in 10 hours.

Now here's the catch. It's not a very complex catch, but it brings a lot of people undone!

If you gloss over everything else read this carefully:

Firstly, don't think too much about the "hour" part in Amp hours. The time is fairly irrelevant to the battery itself, it's more relevant to how long you run an appliance, or in techy talk; put a load on that battery.

Think of the battery as a fuel tank. Think of Amp hours as litres of fuel. A reasonable analogy is one that applies to older diesel engines. Before self bleeding diesel engines existed, running out of fuel could cost you dearly. An empty fuel tank would mean having the engine professionally bled!!!!

A similar principle applies to AGM batteries. If you let them run down to empty, it's going to COST YOU. Every time an AGM battery falls below 50% capacity, think of it as an empty tank. By emptying it that much,  the batteries lifespan is reduced by a not insignificant amount. If you want your expensive AGM batteries to last (up to 7 years for some), treat them well and don't discharge them below 50% DoD, because they'll soon be DoA. 

The best way to meter your battery's capacity easily is to read the voltage. Most "intelligent" chargers or solar regulators display the battery voltage. There are also some very inexpensive meters, widely available.

50% capacity for an AGM battery or bank of batteries is around 12.2v. Different battery manufacturers publish charts showing 50% DoD anywhere between 12.05v and 12.3v. I use 12.2v as a general guide, bearing in mind that a battery that is under load will show a lower voltage with the DoD at 50%. If a battery shows 12v first thing in the morning with a load on it, you're fairly guaranteed that you haven't done any serious damage to it. I tend to aim for a higher figure to be on the safe side. If my battery bank shows 12.1v first thing in the morning, under load, prior to the sun hitting the solar panels, I'm happy.  

The basic rule is to work out your daily consumption in Amp hours and at least double that figure in terms of battery capacity in Amp hours. If you are likely to consume 100 Amp hours per day, you will need at least a 200Ah battery bank, but that's kind of pushing it really; leaving no latitude. In my set up, we consume around 40 Amp hours per day. Our battery bank is 240Ah. That's more like the figure you should be working towards. It leaves you with a lot of capacity up your sleeve in case of low charging rates, such as solar charging during periods of low sunshine. 

Charging

There are three widely used methods of charging house batteries:

Solar panles

240v mains charger.

Tow vehicle alternator.

Solar Charging

I've covered solar charging in a couple of previous posts, so rather than bore everyone with the same information again. I'll summarise the basics.

Solar panels are connected to a solar regulator, which regulates the charging of your batteries. It's essentially a battery charger that's powered from the sun. A group of panels connected to a single regulator is called an array.

Many forums advocate the use of MPPT solar chargers, claiming that you get more charge from less sun. I won't get into the technical nuances of solar regulators, but will say that an MPPT regulator is far more effective if your array of panels exceeds 600w. A good quality PWM charger will suffice for smaller arrays and cost you much less money than a quality MPPT unit. I'm not saying that MPPT regulators don't employ better technology, they certainly do. I just personally feel with smaller arrays, the cost can far outweigh the benefits. In some instances, high quality PWM regulators such as those made by Victron, are better than lower end MPPT regulators. On the other hand, low end PWM regulators are often bloody useless. 

The charge that a panel generates is generally measured in Watts. 

A 100 Watt solar panel produces approximately 6 Amps of current in full sun. That means that 6 Amp hours of charge would be absorbed by a battery in one hour of full sun, with the sun closest to the earth's surface ie at midday. Given the movement of the sun from east to west from sunrise to sunset, a 100 Watt panel will produce around 30 Amp hours of charge on a cloudless sunny day. 

If you have a 100 Ah battery, given that it's not advisable to discharge a battery below 50% DoD, no more than 50 Amp hours.should be discharged in a day. To regain 50Ah per day,  you,  would need a 200 watt array. 

It's a commonly held belief that your array should be double in Watts,  what your battery bank is rated  in Amp hours.

100 Ah battery bank - 200 Watt array
200 Ah battery bank - 400 Watt array

It's far from a firm and fast rule. Array size is also determined by daily consumption. 
I have a 240 Ah battery bank and a 460 Watt array. According to the above guide, I would have a 280 Watt array. However, I don't draw anywhere near as many Amps from my battery in one day as is generated by my array. My array produces an average of 85 Amp hours in a day in good weather. I draw around 50 Amp hours from the battery bank, per day on average. My setup is fine for sunny weather. One might even suggest a smaller array.  I could probably do with adding another 100 to 150 Watts to my array to compensate for cloudy weather. However, I have a generator for topping up the batteries when necessary. Array size is to some extent, a case of "horses for courses." An array can certainly be too small in electronic terms, but not too big. On the other hand, it can be too big in terms of size weight and cost. It's about finding a balance. 

A Solar charge regulator

240v Charging

A 240v powered intelligent charger is, in my opinion, an essential part of any 12v set up. Regardless of how effective your solar charging is, there's always going to be a need to plug into a 240v supply and put the battery bank through a very reliable, continuous charge cycle that doesn't depend on available sunshine. This might be when the sun just isn't providing and charging takes place by means of a generator. It might be simply when you're on grid and plugged into a 240v supply, which is a great opportunity to give your batteries a good solid charge.

An intelligent multi-stage chargerter
 and an old  (now deceased) dicky inverter

Many intelligent chargers will analyse your battery and if necessary, put it through a regeneration cycle, which has the potential to repair a battery that has been damaged to some extent, by being over discharged or being discharged too quickly.

Most intelligent chargers allow selection of the charge rates up to 50 Amps. The charge rate can be explained as simplistically as the amount of Amp hours (litres of fuel) that are put back into the battery (fuel tank) in 1 hour. It isn't quite so simple due to the nature of multi stage charging. To explain further: One would expect that a 25 Amp charger would charge a 100Ah battery from 50% DoD in in 2 hours. in realty it will charge the battery to around 75% full in around an hour. 25 Amp hours added to an existing  50 Amp hours, taking it up to a 75 Amp hours  or 75% of capacity. At approximately 75% full, the charger will automatically switch stages from "bulk" to "absorb" charge. The charging current is reduced in order to prevent the battery from over heating and over charging. As a result of the reduced current, absorb charging can take considerably longer than bulk charging; often around 3 hours to charge the last 75% of a 100 Ah battery.

Charging From A Vehicle

Many Australians say, there's no such thing as a free lunch. I hope it's not entirely true, because I've had hundreds and I don't want to get a surprise bill, but the general gist of the euphemism is true.

If you're going to gain from something somewhere, you'll pay elsewhere. Charging a house battery from a vehicle is a bit like that. A vehicle's alternator is a readily available source of a charging voltage, but a load on an alternator is inversely proportional to fuel consumption by the engine that drives the alternator. It's not a huge consideration, but it is one to be aware of and should not be over looked.

From a personal perspective, we don't charge our caravan house battery from the car's alternator. We have a significant solar array on the roof of the caravan and that generally suffices as far as our charging needs go. We also have a second deep cycle battery system in the car that powers our Engel Freezer. That is charged from the alternator via a simple battery isolator.  The isolator ensures that the Auxiliary battery doesn't charge if the car battery is below a nominal voltage. That prevents draining the car starting battery. It also ensures that charging ceases when the Aux battery reaches a certain voltage, thus preventing over charging. Battery isolators are a compromise in that they don't offer multi stage charging as outlined above. They essentially cut off charging prior to the battery reaching full charge, where a multi stage charger drops the charging current in absorb charge mode, then continues to maintain the charge in float mode.

Multi stage charging is easily achievable via a vehicle's alternator with a DC to DC charger. This type of device is an "intelligent" multi stage charger that's powered by a 12v DC supply from the vehicle as opposed to a 240v mains supply. They are usually connected between the vehicle and a caravan or trailer via a significant cable of sufficient diameter and Anderson plugs. They usually charge at a rate of around 15 Amps, some up to 25 Amps.

Decent DC to DC chargers are reasonably expensive. They're potentially an extravagance unless you spend a lot of time towing as opposed to staying in one place for long periods. However, the up side is that a lot of the better models also double up as a solar regulator, which makes them quite cost effective. In saying that, even the good ones aren't necessarily the best solar regulators. 

Given that I prefer to hang around in places for a while and travel as infrequently as possible, it's not worth me spending a lot of money on a DC to DC charger. A simple battery isolator serves my purposes well, given that we rarely travel for more than 4 hours in a day. This means that my battery is essentially bulk charged on the road, then plugged into a separate solar regulator for the later stages of charging. 

Inverters

Starting an online thread relating to inverters, can be to open a can of worms, which makes about as much sense as the non existence of a free lunch , but you know what I mean.

There are two main misconceptions about inverters: 1) That if you have a 600W inverter, it will produce 600 Watts of power, whenever it is switched on. 2) That they are magic! - Some people honestly believe that by plugging in a powerful inverter, they are magically transforming their 12v DC supply into a mains supply, providing and endless source of 240v AC electricity.

Debunking number 1 - Inverters only produce whatever power is required for whatever is plugged into it. Let's say you have a 600W inverter and you plug a 300W stick blender into it. The inverter will consume 300W. Let's say the stick blender operates for 3 minutes and use our important equation from earlier to debunk number 2.

P - 300W (Blender) /  V - 12v (battery supply) = I - 25 Amps

In one hour of continuous use the stick blender will draw 25 Amps from the battery.

This is where we get a little tricky. Inverters operate with an inefficiency of around 15 to 20%, that means. When calculating how much current is drawn using an appliance via an inverter, we can allow for it's inefficiency by substituting 12v (V) in the equation with 10. There for V = 10.

So the equation would be 300W / 10 (V) = 30 Using a 12v DC supply via an inverter to power a 300W blender, it draws 30 Amps.

To calculate how much it draws in 3 minutes, is pretty simple 30 Amp hours / 60 (minutes) = 0.5 Amp hours in 1 minute x 3 (minutes) = 1.5 Amp hours

I (current) / t (60 minutes) = I per minute x t (minutes of use) = Current Drawn

In summary, using a 300W stick blender for a few minutes, doesn't draw much from the battery. About 1.5 Amp hours. 

Inverters can be used in a couple of ways. I've taken a line out of the 240v outlet on the front of our inverter and wired that up, so that it can be switched into the caravan's main 240v circuit. This allows us to use our power points and 240v lighting, which has all been upgraded to LED globes. It's also possible to keep the invertor in a convenient location and plug appliances into its front panel as required. 

When an invertor is left on without actually providing power, it is in a state known as "idling." Idling generally draws less than 1 Amp, however 1 amp over 24 hours is still 24 Amp hours. Good inverters run in standby mode, which means they idle for less time and power up as required.

I personally believe in buying a quality inverter, but not going over the top. Some can get into the thousands, quite unnecessarily. There really isn't any point in buying a big inverter to run powerful appliances. They put a huge drain on battery banks and need to be hooked up with seriously heavy gauge cabling and breakers, in order to prevent the risk of fire. If you really need powerful appliances when you're off grid, either get a generator or re-think your priorities. Do you really need the microwave that badly?

To buy a good quality (and I mean safe), high powered inverter, you're looking at $1,500 plus. I had a cheap Chinese on that cost 80 bucks, for years. I wanted it to die so that I could justify buying a good one. I couldn't kill the bloody thing, when it did eventually bite the dust, it took a few hundred bucks worth of appliances with it.

A very good 400 to 600W inverter can be purchased for around $300. Carry on reading to discover why it's not worth having anything much bigger. There are 2 types of inverter in terms of how their supply voltage "cycles." A pure sine wave invertor is the only type I recommend. It provides 240v supply that's probably more stable than most mains supplies. A lot of technology, especially laptops require a pure sine wave inverter to operate. A "modified sine wave" inverter is good for lights and electric motors, but won't run and could even damage complex technology. It's not worth buying anything other than a pure sine wave model. 

Quality Victron inverter

NOW KETTLES!!!! (and other unnecessary things that heat)

One of the most commonly asked questions is "what size inverter do I need to boil a kettle?"

Let's look at an average kettle as having a Wattage of 1,800W

Let's look at the average boiling time to make a cuppa as 3 minutes.

We'll assume that the person who possesses a fear of gas stoves, also possesses an inverter big enough to boil an average kettle. The inverter size is irrelevant. All that is relevant is that it can handle 1,800W.

So, strap yourself in for some simple maths with significant results!

1,800W / 10 (V) = 180 Amps - Boiling a kettle continuously would not only take a 100 Ah battery lower than it's recommended DoD (Depth of Discharge 50%), it would actually flatten it in less than one hour!!!

What's that I hear you say? "It's only going to boil for 3 minutes!"

OK then, now that we have a figure of 180 Amps let's look at the equation that calculates how much current is drawn in a given period.

180 (I) / t (60) = 3 Amp hours (I per minute)

3 x 3 (t - minutes of use) = 9 Amp hours

9 Amp hours drawn from the battery to make 1 cuppa. If you have a 100 Ah battery, 5 cups of tea in a day would discharge the battery to a suitable DoD. 2 cups a day would constitute over a quarter of available power.

There's a very easy answer; use a gas burner and a stove top kettle. Appliances that heat, simply draw too much current.

Lithium

There's is another option for running more powerful appliances, which is Lithium batteries. Lithium batteries are considerably lighter than AGM batteries, therefore you can have large banks without having a huge effect on the caravans weight. A 100 Ah AGM weighs about 30kg whereas a 100Ah lithium battery weighs about 10kg. The other huge advantage of Lithium batteries is that they can be discharged to over 80% DoD, therefor they're considerably more efficient than AGM batteries.

Now the bad shit! Personally I don't like the concept of lithium batteries being touted as the be all and end all of renewable energy. Lithium is a finite resource. A reasonably valuable finite resource. Currently $9,400 per metric Tonne. It has doubled in 4 years and isn't going to get any cheaper. It's more water intensive than lead in terms of extraction and unlike lead which is currently $2,300 per tonne, is economically impractical to recycle. 

Guess which country has the world's largest Lithium deposits. Yes, it's us again. We aren't the biggest producer, Yet, but explorations have identified huge deposits. So, guess who's backyard is going to be fucked up most by the increase of lithium battery use? Yes ours. 

So, think about those CMCA members in their big busses who feel entitled to exclusive rights to free camps because they are environmental saints for having fitted grey water tanks. Not only are they fucking the environment with their carbon emissions, a lot of them are helping the destruction with their bloody great lithium battery banks. 

I must add, I don't have a personal problem with them, as long as they don't cast environmentally based dispersions on people who pour a little bit of water on a tree. It's hypocrisy of the highest order, based purely on financial elitism. It's NOT environmentalism. They're not fooling anyone. 

I have been accused of being "anti-big rig." I suppose I am, but that doesn't mean that I don't like the people who own them. I generally get on with people. I'm also anti over investment in the housing market, yet many of my close friends have done it. 

My problem with "big rigs" is that they defeat the principal purposes and purpose principles of downscaling. Especially given that many owners don't even live in them permanently. For me and many others, downscaling is political. It's a means of survival. I just feel that in many cases "big rigs" display an over reliance on wealth. I don't have a major issue with unnecessary wealth. I have an issue with wealthy people who regard those who struggle, as enemies of the state. The biggest problem in this country is insanely wealthy people who don't pay taxes. Now, talking about Gina; back to mining lithium. 

It's very interesting that Tesla one of the world's biggest producers of Lithium batteries, is sneaking it's way under the bed covers of both state and federal governments. Call me a cynic, but I have a sneaking suspicion that the sudden benevolence displayed by Elon Musk and Tesla towards Australia, might just have something to do with them getting their filthy mitts on our resources. 

We've seen the disastrous results of our national grid being sold off to private investors around the country. That's only a small taste of the public being fucked over, in comparison to what's going to happen if Tesla achieve world domination.

OK, there's my political rant over. Well nearly. I have to add that it's a very sad indictment on Western capitalism, when something as positive for our future as renewable energy, is allowed to be turned into a monster by government / corporate cronyism!

So, that's the political bad shit about Lithium. Most people reading this probably won't give a shit about that, so I'd better also point out that whilst an 100Ah AGM battery can cost as little as $200, a 100Ah Lithium battery will set you back over $1,000!!!! The charging equipment for Lithium batteries is also considerably more expensive than for AGM batteries. Also, if you're going to have a huge battery bank, you're going to need a hell of a big solar array and somewhere to put it. My personal advice to anyone, be they in a home, caravan or motorhome, is scale back your usage and make do with as small a system as you can.

Not all lithium stops me from being mad!
Lithium batteries make me MAD!!!

Fuses, Breakers and Cable Ratings

Everything in a 12v system needs to have a fuse or breaker in line. A fuse contains a wire that burns out and breaks when a current greater than is required to supply an appliance passes through it. It breaks the circuit rendering it safe. Once the problem has been isolated the fuse can be replaced with a new one.

Breakers perform the same task as fuses, only they are somewhat more complex in that they are a switch mechanism that is activated, breaking the circuit when a current greater than it's nominated value is detected. 

The most common reason for a fuse or breaker being activated is a short circuit. A short circuit occurs when there's some sort of connection between the positive and negative sides of a DC circuit. This can result from wires or terminations making contact with each other, or contact being made through conductive material that is making common contact with each side of the same circuit. 

Whilst 12v DC circuits don't carry the same risk of electrocution that 240v DC does, a 12v short circuit can easily result in a fire with catastrophic results. In my opinion, 12v DC installations can be more dangerous than 240v installations. You don't have to be qualified to do the work. Terminations are not required to be of the same high safety standard as 240v AC and people fear 12v DC far less than 240v AC, due to the significantly lower risk of electrocution. As already stated, the risk of fire is indeed great, so BE CAREFUL. Read as much as you can and don't attempt any installation until you are absolutely certain that you can do it safely and avoid short circuits. It's probably a good idea to get your first few installations safety checked by an auto electrician. It's a small price to pay for safety.

Personally I use breakers instead of fuses on everything. It's easier to re-set than replace and they allow more convenient isolation of a problem. If a breaker trips after you have "fixed" a problem, you know you haven't fixed the problem. The same applies to a fuse, however every time a fuse breaks, it has to be thrown away and replaced with a new one. You can go through a lot of fuses while isolating a problem.

I have also seen examples of blade fuses burning out but actually fusing open circuit as a result of the metal melting. This could result in an ongoing  short circuit, which could in turn result in a fire. 

I tend to use "blade breakers", which look like a typical "blade fuse" that you fins in a car's fuse box, only they're black with a little red re-settable button in the top. They don't seem to be very popular. I think there's a common misconception that due to their less than imposing size, they're somehow less reliable than seemingly more solidly built breakers. I've been using them in my caravan fuse box for nearly four years. They are extremely reliable. I've never had one fail. They don't trip unnecessarily and I've tested their effectiveness on a regular basis. They're excellent. They cost considerably less than seemingly more substantial breakers and take up considerably less space. They fit into a typical automotive fuse box.

Fuses and breakers are rated in amps. gauging a fuse rating isn't rocket science. I work out the sum on the maximum current that can be drawn on a particular circuit and round off the fuse value to the next highest value. For instance, if the sum of all of your 12v fans in use at the same time is 4 Amps, the next highest value is a 5 Amp fuse or breaker. This allows for some latitude. They won't trip the circuit if the current drawn surges slightly and goes above the nominal total current value a little bit, but if a short circuit occurs the fuse or breaker will trip safely. If the fuse or breaker rating is too high for the circuit, problems can occur without it tripping. This can result in damage to equipment.

The same principle applies to cable diameter, which in turn corresponds to current rating. However, if the current in a cable is too high for what it's diameter allows for, it obviously won't trip. Instead it will overheat with great potential to start a fire. Wire diameter which corresponds to current rating, should match fuse or breaker values. 

This post is designed as a brief guide. I seriously suggest reading considerably more on breakers, fuses, cable rating, schematics, terminations and joiners, prior to undertaking any installation work. 

Blade fuse box with blade breakers inserted

The 3-Way Fridge Trap

That sounds like some kind of bizarre criminal activity by a psychotic serial killer, but it's not. At least not yet anyway. 

3-way fridges run on gas, 240v electricity and 12v electricity. 

I keep reading about people with the same problem; "my 3-way fridge is draining my battery quickly."

This is very simple. This style of fridge runs by means of heat exchange, unlike others that run by means of a compressor. Compressor fridges, such as Engels and Waecos for instance, are very energy efficient. Heat exchanger fridges are very energy inefficient. Some  can draw up to 25 Amps, whilst a similar size compressor fridge will draw between 1.5 and 3 Amps.

3-way fridges are designed specifically to run on LPG when off grid and 240v AC when available. The 12v option is for the specific purpose of powering the fridge whilst the vehicle is moving, with a direct connection to the alternator. 

We have a 2-way fridge. We tend to use our freezer to pre-freeze ice packs prior to a long journey. We pack the fridge up with them for the first part of the journey, leaving the fridge turned off. We then connect the fridge to 240v via the invertor for the second half. Our fridge is more efficient than some and we are continuously charging the battery bank via solar panels on the roof as we travel. We usually end up with a reasonably full battery and cold beers when we arrive at our destination.

If you have a 3-way fridge, it's meant to be powered by LPG gas when you're off grid. Running it from a 12v battery will drain the battery very quickly. Don't do it, or if you do, don't whinge on the internet because you've been told.

Our kitchen with our 42 year old Electrolux 2-way fridge

Points to Remember

Batteries and battery banks are measured in Amp hours

Amp hours are like litres in a fuel tank

P (Power) / V (Voltage) = I (Current) - That's how to calculate how much "fuel" you're using

A deep cycle battery is designed to deliver a low currently continuously over a long period of time, whilst a car / cranking battery is designed to deliver a high current in a short burst to start a motor.

You're battery or bank should never fall below half full (50% DoD)

Voltage indicates how full a battery is - 12.2v is about half full.

A group of solar panels is called an array. Measured in Watts.

In full sun, 6 Amps is generated by every 100 Watts in an array.

Solar arrays are connected to solar regulators. Good solar regulators are intelligent multi stage chargers. They ensure a full charge and prevent over charging.

As a suggestion, an array should total in Watts, twice the size of a battery bank in amp hours. For example - 200W battery bank requires a 400W array. Not a hard and fast rule. 

A good 240v intelligent charger is important for putting your batteries through a good continuous charge cycle when mains or generator power is available. They are also a very good means of regenerating batteries that have been over discharged.

Charging from an alternator / vehicle is very convenient if you travel regularly. Always bear in mind that gained energy is paid for elsewhere. Charging from a vehicle will increase fuel consumption.

DC to DC chargers provide multi stage charging from a vehicle. They are reasonably expensive and might be unnecessary for people who don't move on from a location regularly.

Battery isolators can be used in place of DC to DC chargers. They are very inexpensive, but only provide a bulk charge. They will never completely charge a battery because a solenoid cuts switches charging out at a nominal voltage in order to prevent over charging. 

Battery isolators also prevent a car / cranking battery from being discharged when a house / aux battery reaches a nominal DoD.

A house or aux battery can be bulk charged by a vehicle via a battery isolator whilst driving and then switched over to solar charging for final stage charging with a reduced current. 

Inverters transform 12v DC from a battery into 240v AC for powering domestic appliances.

When an invertor is left on but no appliances are being used, the invertor is "idling." It does not use run at it's rated power (wattage) when on but not powering an appliance. Idling draws a very small current.

Invertors are not magic. They are only as capable as your battery bank. Large invertors are often a waste of money. They can provide a 240v supply to appliances of a high wattage, but they'll suck batteries dry in a hurry.

Lithium batteries are expensive, evil and the core of world domination by a US power giant. (Shit that's going to cause some arguments - good job I enjoy being insulted by people who I've insulted because they just spent a fuck load of money on lithium batteries)

Fuses, breakers and correct cable ratings can save your equipment or possibly your life by preventing a fire. They're designed to ensure that a circuit does not carry a greater current than it's supposed to.

Fridges that run on LPG gas are supposed to run off LPG gas when a 240v AC supply is not available. If you run one from a 12v DC battery, you will discharge it very quickly, so don't do it! If you do, don't whinge about it online, because now you know not to and it's your own fault if someone calls you a goose. 

Watching, Listening and Communicating - IT and AV for RVs

Mobile "Interwebs"

One of the most popular subjects on internet forums, is the cost of the internet itself. I follow a lot of caravaning and camping pages and I notice that there are daily questions about mobile phone and data services. It's a bit of a Lion's den, given that everyone's needs are different and there are hundreds of options available.

One of the most commonly espoused opinions is that you "have to be with Telstra, if you are travelling." I've bought into that for years and there is indeed a degree of truth to it. Telstra coverage in regional ares is undeniably superior to their competitors. Network roaming was on the horizon more than ten years ago. That would have meant that people who were with other carriers could have made calls on the Telstra network, in areas where their carrier didn't have coverage. Vodafone and Optus were very keen, but Telstra did whatever they could to block network roaming and increase their regional monopoly. 

Mobile broadband modem in it's specially designed porthole

In may 2017, the ACCC ruled that Telstra weren't maintaining a monopoly and decided to support their stance. Interestingly over 95% of Australians live in cities where Telstra's competition offer very acceptable coverage. Telstra's monopoly in the bush isn't enough to give them an overall monopoly. Their hold on the Australian mobile phone and broadband market is loosening rapidly, largely due to high data costs and dissatisfaction with customer service . It'll be interesting to see what Telstra do with their regional monopoly as their urban market fails. It's hardly worth them maintaining it, but they're bound by a commitment to provide coverage to a nominal percentage of the population. I predict that Telstra will eventually become just a mobile network facilitator, not a telco as such. They're bandwidth and coverage will become available to any telco that's happy to pay a fee. It's an optimistic prediction, but despite dropping charges dramatically, the rot has set in and the mass exodus from Telstra has begun. It's going to take more than reduced data charges to save their monopoly.

Whatever the future of coverage in Australia might hold, I do indeed have a mobile contracted to Telstra and the coverage is excellent. For the time being I'll keep it with Telstra for that reason. Even so, I feel that I'm being ripped off by the contract I'm locked into. I re-contracted a year ago. My contract costs $75 per month with unlimited national landline and mobile calls and certain international calls. My data allowance is a tiny 3Gb per month with excess data charged at a huge $10 per Gb. To make a simple comparison; with mobile data costing as little as 70c per Gb, $10 per Gb is the equivalent of paying $22 for a can of Watties Baked Beans! 

Within a year of me entering my contract, the same call quota plus 12Gb of data was being charged at $50. After about 2 weeks of "sport whinging" to the Telstra Contract Retention Team, I managed to get 10 bucks a month knocked off my contract fee and a total of 8Gb of data, but still "not happy Jan!" 

We home educate our daughter and like most teenagers, she loves to stream video online. Why wouldn't she. The internet is important to us. I know that statement is often maligned by the neo-Luddite types who see the "interwebs" as the root of all evil, but it's the way the world works these days. You're looking at it now. Telstra's data charges just can't work for us.

Following a few experiments, we ended up using Optus as our main internet provider. On their month by month post-paid My Mobile Broadband Plus 100 package, we get 100Gb per month for $70. It's a hell of a lot of money on top of my $65 per month with Telstra for phone, but I can't get out of that. As soon as I can, I'll switch to a pre-paid service on the Telstra network for phone, that should cost me around $30 per month, with a little bit of data for maps, social media and Wikicamps for when we're travelling. 

Optus coverage can be patchy, but it's fairly ok in most small urban areas. We just have to accept that we won't be streaming from Netflix when we're in remote areas. Somehow, I don't necessarily think that's such a bad thing. I still have 8Gb a month with Telstra for internet essentials, such as educational resources for our daughter, when we're off the beaten track. On the flip side, one massive benefit to our Optus package is that as well as 100Gb, certain types of streaming are un-metered. We can stream unlimited data from Netflix and music from spotify, without using up our data allowance. 

It's a BYO modem deal, but mobile broadband modems are cheap. I bought a fairly decent unlocked 4G modem from ebay for $45. One thing to note, is that if you do get into a deal with un-metered streaming such as Netflix, DO NOT stream via Chrome. Stream directly from the app. Anything streamed from via chrome will simply be metered as a Chrome download. That's a bit of a trap for young players: and old ones like me who only discovered that when I noticed my daughter was clocking up 7Gb per day. 

There are many, many options for streaming movies and TV shows. You can use a smart TV, Google home, Chrome Cast from a device, a device connected via a HDMI cable, in fact far too many methods to even attempt to list. I'm going to provide an outline of our setup, but I'm by no means saying that it's the best option. It just happens to be very cost effective.

We have a Kogan 24" full HD LCD / LED TV with a built in DVD player that we rarely use. It's mounted on a flexible arm on a bulkhead facing our lounge area. These particular TV sets cost around $200. They're lightweight and the picture is very good for the price in my opinion. As far as audio goes, they are essentially un-listenable. The speakers are of ridiculously low quality, under powered and housed in a space that prevents reproduction much below 400Hz. They are fucking dreadful! Fortunately that is very easily and cheaply remedied. More about that later. 

Apple TV - A cost effective way to make a cheap TV "smart"

About five years ago, when we lived in a house, we bought one of the second generation Apple TV streaming boxes for $100. We used it about 5 times to stream via iTunes, but found it very expensive. The upside is that there are a number of streaming channel options on Apple TV, including Netflix, Stan, Youtube and hundreds of internet radio stations. It's a tiny unit and has sat in the caravan, unused for some years. When we finally got onto a decent mobile broadband deal with un-metered Netflix streaming, I looked at spending $80 on Chrome cast, enabling me to connect form my computer to the TV wirelessly. Then I remembered the Apple TV box. I attached it to the back of the TV with velcro pads, connected it to WIFI, plugged it in with a HDMI cable, updated it to the latest software version for free and hey presto, we had a smart TV with streaming available with the click of a remote. As I've already stated, there are many many options. This was the one we opted for because we happened to have the hardware stashed away in the caravan. However, with second generation Apple TV units available from the US on ebay for as little as $50, it's not a bad one. 

Listening

As someone who spent the first 25 years of their working life as a recording engineer in the television and music industries, I take listening very seriously. I can't bloody stand poor audio reproduction. I can accept that a caravan is hardly the best environment in terms of acoustics, but I do what I can to make whatever improvements that are possible within my budget, which is three fifths of fuck all.

I walked into JB Hifi with around 400 bucks to burn on a Bluetooth speaker system. I admit that Bluetooth audio is somewhat of a compromise, but I tend to listen to WAV files that I've burned from my CD collection, which even via Bluetooth, sound better than MP3s via a cable, in my opinion. Bluetooth is also an improving technology and later generation codecs, for instance apt-X offer much better audio quality than the early Bluetooth headphones that were rather nasty. 

Bluetooth compression aside, everything I listened to with a price tag below $400, sounded like a bucket of sick! The speaker quality in the units that I heard was invariably dreadful. There was absolutely no way I was going to part with my dough. Some of them weren't even stereo units for over $300. On the way home, I dropped into my favourite geek Mecca, MSY Technologies to buy an SD card. I saw  Creative Labs Inspire 3300 active 2.1 (left, right and subwoofer) computer speaker system for $59. I thought it couldn't possibly be any worse than any of the units that had just auditioned, so I bought it out of disgust.

Kogan TV with very expensive speakers

I got it home, plugged my PC into it and cranked it up. I had to call my wife to ensure me that I wasn't experiencing auditory hallucinations in some kind of flashback from my very misguided youth. It sounded absolutely fantastic and it had just cost me sixty bucks!! Creative Labs isn't just some logo stuck onto nasty OEM manufactured products. They're a Singapore based technology company that make some pretty clever stuff. They've been around for years and were the developers of the highly successful Sound Blaster PC sound card. It's a mystery how and why they manufacturer such great products for so little. The build quality is pretty cheap, but the audio quality is outstanding

The subwoofer, which is also the amplifier and power supply, fits perfectly on a shelf behind a thin plywood bulkhead, which also acts as a very effective low frequency resonator. The sub has a separate level control, so one can prevent it from being overpowering in a small space. Unlike many 2.1 computer speaker system, the crossover point between the left / right speakers and sub is very well placed. The very compact LR speakers have an effective low frequency port system and go down relatively low, preventing that notorious void between the 2 and the .1 in budget systems. They sound fantastic! 

I set about making a flat bar that fits to the back of the TV support arm with the speakers mounted on it, either side of the screen. It works very well. I ran a cable from the TV's audio out, into the amplifier and instantly transformed the worst sounding TV I've ever heard, into one of the best. In fact the audio graphic equaliser on the Kogan TV is quite good. It's just the speakers that are totally shit! My next addition was a Bluetooth receiver, so that I could wirelessly connect music from my devices. It's a very small box that cost me $29 from MSY and fixes with a velcro pad to the amplifier. I really didn't want to have to connect and disconnect cables when swapping between TV and audio from devices, so I bought a little passive router switch with gold plated RCA contacts for $18 from ebay. I have also attached that to the side of the amplifier with velcro. The amp / subwoofer stands on small feet. These have proven invaluable as i have been able to wind all excess cable around them and secure them tightly with small cable tires. Any cables that run between the speakers, TV, router / amplifier, do so via a single flexible conduit. It's all very tidy. 

The audio nerve centre

Nobody, even those with very grand caravans, has ever walked into our home and not been impressed with the AV set up. The system consists of 4G modem $45, TV $200, Apple TV $50, 2.1 Sound System $60, Bluetooth Receiver $30, Router $18 and a few cables $30. That's about $430. 

This stuff can be done very cheaply and very easily. The trick is not to get sucked into marketing. Cheap technology can be really nasty, but as I learned from my trip to JB Hifi, big names and big price tags, don't necessarily mean quality. 

Staying Warm, Keeping Cool Without Burning The Budget

When I look at a lot of modern caravan / RV setups, I realise that some people spend more on heating and cooling combined, than we spent on our caravan. In fact, some people spend more than what it costs to purchase heating and cooling systems for the average home.

I don't know a hell of a lot about heating, because I generally negate the need for it by travelling north. We also have a full size gas oven in our caravan and roof top extractors. If we ever are in the unfortunate position of being where the temperature drops below 20 C, we can heat the van up fairly promptly by lighting said oven. The extractors remove carbon dioxide and provided that there's a small window partly open, oxygen flow into the caravan is ample. There are people however, who don't mind punishing themselves through travel in cooler climes. Again and again I meet people who own both rooftop reverse cycle units, which heat and cool, as well as diesel heaters. We're talking around $4,000 worth of appliances, after installation costs. Throw in a generator powerful enough the run the rooftop unit off grid and we could be talking as much as $7,000.

Carframo Ecofan Belair stove top fan

I'm not here to start a war over what type of appliances people should have, but I will say that's a hell of a lot of money and way out of reach of low income earners. I hear a lot of good things about diesel heaters. They're quiet, efficient and cheap to run, but at over $1,000 a pop plus installation costs, that's a lot of money just to heat a small space. As previously mentioned a gas oven or stove in a caravan can provide a fair bit of heat, but admittedly it's quite inefficient given that you have virtually no control over the flow of warm air. If you have around $250 to spare, you can turn a very low burning gas stove hob into a very efficient directional heater. The Canadian made Caframo Belair is a stove top fan that uses conduction to not only to provide heat, but also to generate electricity to drive a small fan that blows that heat in whichever direction you wish. It works very efficiently with a small flame. The smaller the flame, the smaller the amount of carbon dioxide that's produced as a result. some ventilation is obviously required, but personally I wouldn't run a diesel heater without ventilation in such a small space either. 

The stove top heater probably isn't as convenient as a diesel heater. Despite being small, it still needs to be stored away for travel. At around $800 to $1,200 less than a diesel heater after installation, it's most likely worth the slight inconvenience for those who don't have money to burn - excuse the pun. If you're not off grid and have a source of 240v electricity, there are a number of very compact and cost effective options for heating. Caframo's True North is designed for the marine market and is therefore extremely rugged. It has 600 and 900 Watt settings, which means that it can run off a small generator if so desired. They cost around $200. 

With a somewhat higher price tag at around $330, Nobo's 750 Watt wall mounted electric convection heater is also an excellent option for caravans and RVs. At only 630mm wide by 400mm high and 55mm deep, it should fit on a wall somewhere. They're highly efficient and can be run by a 1 KVA generator. Given that you can pick up a fairly decent 1 KVA generator for under $300, for between $550 and $750, you can heat your caravan / RV and get yourself a small generator that'll be extremely useful for general off grid living.
For $250, you have the convection fan option and for the cost of a bit of gas, you can just use you're oven or stove and some blankets. 

Whichever option you take, I don't really think diesel heaters are for the low income earner, or anyone who cares about how much they spend. It's another one of those things that "you have to have." I've seen a number of forums and Facebook posts where people have asked about low cost heating solutions. Oh look, here comes 60 plus bearded Akubra wearing man. "You have to have a diesel heater. I have a diesel heater. You can't camp here without one. It's Un-Australian!"

I'm not hanging shit on diesel heaters, they do the job extremely well, but do the sums. Is it really worth over $1,000 to heat spaces that on average are around 140 sq ft? That's a hell of a lot of money. I'll be so bold as to say it's a bloody extravagance. When someone is asking for advice on a low cost heating solution, I couldn't think of worse advice than a diesel heater. It might sound like i'm on an anti-diesel heater crusade, but that's not the case. I'm on a crusade against online forums that are dominated by advice from people who don't have to survive on a low income. Sure they're entitled to give whatever advice they like, but it's relentless. I often witness people expressing despair because they think they'll never be able to afford to live on the road. Every time they ask for advice about anything, they're told that they'll need to spend immense amounts of cash and that anything else 'just won't do.' It infuriates me, because it's such bullshit. 

Air conditioning can be an even bigger expense than heating, but doesn't necessarily need to be an exorbitant cost. Getting warm is considerably easier than staying cool, therefore mechanics are somewhat more vital. Whilst air conditioning most definitely isn't essential, it can prevent significant discomfort in the hotter months and in the hotter regions of Australia. I suppose air conditioning could be regarded as a luxury, but sometimes when I come back from a long, hot fishing trip, it feels quite essential. A cool caravan is indeed very welcoming. We also enjoy good food and often entertain. We make the most of our kitchen setup, including the oven. A lot of people are happy to limit themselves to cooking outside on a gas grill, but we're not. The caravan is our home and we wish to enjoy it's full benefits. Air conditioning is absolutely essential if you want to run an oven inside, during warm weather.

 Small, efficient wall unit - back window replaced by a wall and porthole. 

Roof top air conditioners are a pretty standard appliance on caravans these days. There are under bench type air conditioners that vent out of the side of caravans, but they are significantly less popular than the roof top types, which take up less space inside the van. Whether dedicated caravan air conditioners are the roof top or under bench type, they are exceedingly expensive. Considerably more expensive than comparable domestic split systems that are commonly found in houses. Roof top units cost on average around $2,000. Their installation is a major exercise and one can expect to pay a minimum of $1,000. An average area of 140 sq ft. $3,000 is an obscene amount of money to cool such a small space.

Unlike diesel heaters, online forums aren't quite as full of over enthusiastic roof top air conditioner owners. In fact most owners seem to complain about them. People usually acquire them when they purchase their caravans. There doesn't seem to be a huge market for fitting new roof top systems to caravans that don't already have them. Most everyone I've spoken to who does own one, seems to have had problems with their unit, often costing them big money in repairs, only to be left disappointed with the results. They're often noisy, they under perform in extreme temperatures, they're notoriously inefficient and they add a large amount of weight (up to 50kg) at the highest point of a caravan or RV. That's not great for stability. When it comes to free camping, most roof top units require a 3 KVA generator run them off grid. Three KVA generators are big, heavy and obviously noisier than 1 KVA generators. A smaller generator, such as a 1 KVA is sufficient for most needs such as charging and running lights, a television, computers, mobile phones etc. A 3 KVA generator seems like a considerable expense, weight and size consideration just for running an air conditioner that isn't that great anyway.

Generators are a big issue. they seem to be a little like air conditioners; everyone has one, but nobody's game to use one. I rarely witness roof top units running in caravan parks on power and am yet to see anyone running one in a free camp from a generator. It doesn't matter how ridiculously hot it is and how likely you are to expire as a result, you'll be the devil incarnate if you actually dare to run your generator. 

Domestic split systems are often installed as an alternative to rooftop systems, but they have their issues too. Whilst Split systems can be considerably cheaper than rooftop units, they aren't designed for installation in caravans and RVs, thus they're far from ideal. The compressor units are big and heavy. They can be installed either on a reinforced extension from the chassis at the rear of an RV or caravan, or on the draw bar at the front of a caravan. I don't recommend either. Rear weight distribution in caravans is detrimental to stability. Too much weight at the rear will result in fish tailing. Whilst weight distribution that favours the front results in a more stable caravan, you run the risk of increasing the tow ball weight beyond what's acceptable, which can have a detrimental effect on the tow vehicle's front wheel traction. I've also seen examples of draw bars actually buckling under the weight of split system compressor units. 

So far it's not looking good for air conditioners, but every time there's a ridiculously hot day, I'm incredibly thankful that we took the least popular option; the old fashioned window rattler or wall unit. Our unit is far quieter, drastically more efficient, substantially lighter and much more capable of cooling in extreme conditions than any rooftop unit that I've had experience of. It cost us $300. It was a fully warrantied, "factory second," which meant the box was missing. It cost me less than $50 to install. It runs very well for 7 hours on one fuel fill, from our light and compact 1 KVA generator, which is so quiet that people can hardly hear it, so we never get complaints from generator Nazis. The other interesting point as far as free camps go; most grey Nomads are either off the road or way down south in the warmer months. The rest are in caravan parks so they can power their rooftop units from 240v. The net result is that the free camps, particularly in Queensland are virtually deserted. If we want to run our very small generator on an extremely hot night, we can hardly hear it inside and there's nobody around to complain. We haven't looked back.

The southern grey nomad migration in late August, amuses me somewhat. They rush like lemmings because they're inherently convinced that 'summer' is unbearable up here in Far North Queensland. It might get a bit soggy on occasions and I admit the occasional cyclone is problematic, but if heat is a problem for someone, they really don't need to be in temperate or sub-tropical Australia during Summer. South Australia for instance, is the hottest place on the planet during February. Victoria isn't far behind, with temperatures occasionally exceeding 45 C in Melbourne. By September FNQ is deserted, the short mid-year rains have stopped, there's generally an off shore breeze and temperatures rarely exceed 32. September to December at Mission beach is glorious. Just this last summer, I was visiting my family in southern NSW. There was a particular 10 day period when the maximum temperature was no lower than 38 C. It got up to 43 on a couple of occasions. I was looking at Mission Beach on the weather app; 30 and sunny. Those lucky bastards, I thought.   

Our wall unit does one thing and it does it well; it cools. It's not a particularly powerful unit at between 800 - 900 Watts, but it's supremely efficient. Our van is 20' x 8' and it gets very cool in there with the air conditioner on, in full sun on a typical day in the tropics. Even in the extreme heat of southern NSW during the summer, we have managed to keep the caravan internal temperature to below 28 C, in full sun, in shade temperatures of up to 43 C. Most importantly the unit kept going. One of the main complaints I hear about rooftop units is that some simply shut down in extreme conditions. One of the huge benefits of our little rear mounted wall unit, is that I can erect temporary shade over it, if necessary. That's pretty tricky with a rooftop unit.

I suppose the $6.40 question is 'why do we see so many rooftop units on caravans?' I think it's simply a case that we see a lot of later model caravans and they tend to come with them installed by default. It's the easiest place for manufacturers to put them and when it comes down to it, if they don't work so well, the warranty is covered by the air conditioner manufacturer / supplier, not the caravan manufacturer. It's fair to assume that most people who survive on the road on low incomes, don't have flash new caravans, so much consideration should be given to a wall unit.

Our Kelvinator ???? is a fairly light unit at under 30kg. We intentionally limit the weight in the rear of the caravan, so there was enough leeway to handle it. Originally the caravan had a large back window, which was actually the only area with a serious leak issue. It wasn't a hard decision to rip it out, given the endless frustration caused by it's leakiness. We were considering a new window anyway, which would have cost more than our air conditioner. Upon removing the back window and the surrounding timber, we found a significant amount of rot, so we were glad that we started the job when we did.

Stud wall supporting a wall unit air conditioner

Once the back end was ripped out I built what is essentially a stud wall on top of the existing window sill, which is a very strong structural point that can take considerable weight. I left apertures the size of the air conditioner and one big enough to take a small window in the future. The stud wall takes the bulk of the unit's weight, with 2 very compact brackets supporting it from the sill on the outside. We left the window frame in place and filled it with the sheet of aluminium that was in the shutter that formerly covered the window. It might not look a million bucks and I doubt it would be up to the aesthetic standards of the "Mr and Mrs Bucket" type caravaners, of whom there are many, but it serves us extremely well. 

I see some dreadful Jerry built meas of supporting wall units, particularly on older vans. It's not uncommon to see frames welded to chassis with long upright supports. I think this is due to a combination of older units being quite heavy and a tendency to sacrifice the weight balance of the unit in favour of getting the inside control panel as flush as possible with the wall through which it's mounted. Our unit protrudes some 20cm on the inside, but not only is it fairly unobtrusive, it's how the unit is meant to be installed in terms of balancing the weight in order that the bulk of the resulting downward force is on the wall as opposed to hanging out of the back of the caravan. With just 2 small brackets to hold it in place, I can literally hang off the unit without even the slightest chance of anything giving way and I'm a very big bloke. So far the unit has travelled some 30,000 kms without shifting a millimetre.

Rear mounted aircon - Rear window replaced, overhead gutter and flashing fitted to prevent leaks - Sorry it's not clean

On of the most significant issues facing air conditioning in caravans, is that people expect magic defiant of the laws of physics. There's only so much an air conditioner can do as far as an aluminium box in the Australian sun is concerned. Even some of the most modern and expensive caravans and RVs are insufficiently insulated. Getting behind roof and wall skins to improve insulation is a very major, very costly task, but there is much that can be done to make a caravan or RV solar passive. Shade over windows is a good start. It's cheap and easy to run some sail track along the roof line, on the opposite side to the awning. You can run a piece of shade cloth along that and peg it down in the ground in order to keep the sun off the windows. That's simple. The roof is a less surmountable problem, but tackling it can virtually make the difference between being in the shade or full sun, no matter where you are parked.

There are all sorts of expensive caravan roof membranes designed to waterproof joints and reflect heat. They're very expensive and they're very good at sealing joints. As far as the reflection of heat is concerned, any good gloss white enamel spray paint will do just as good a job. Up-market membranes cost between $500 and $800 to cover the average caravan roof. A tube of butyl rubber for the joints and a few cans of gloss enamel spray paint, is only going to set you back around fifty bucks. There are also other far more effective steps that you can take. About a third of our roof space is covered with solar panels. They each have a 20mm air gap between them and the roof. The heat that they absorb is converted into energy, so they actually work quite effectively to provide shade. Solar panels are also expensive and heavy. Whilst I'd like to cover the entire roof, there is a downside to that. That's why I have come up with solar passive panels, which are extremely light and very, very cheap to make.

My solar passive panels consist simply of a layer of foil backed, air pocketed insulation, sandwiched in between two layers of corflute plastic sheet. Simply cut the corflute and insulation to squares of equal dimensions and sandwich them together using contact adhesive, then fill the edges with a 2 part epoxy builder's bog, to prevent fraying in the wind. Stick them to the roof with at least five points of super strong construction adhesive, such as Sikaflex. If you wish, you can stick a piece of plastic angle along the front edge and stick that to the roof. That will create greater wind resistance and lessen the chances of them coming off. The difference the panels can make is substantial. It means being able to park in full sun for the benefit of solar power generation and enjoy the comfort of partial shade.

Other very important factors affecting the efficiency of air conditioners in caravans and RVs is internal airflow and ensuring that there are no points of radiation in the roof. By points of radiation, I refer to weak points in the roof insulation. Hatches can be notoriously problematic in this regard, particularly in older caravans from an era when hatch construction involved the use of a significant amount of aluminium.

Re-modeled 4 Seasons hatch with skylights and solar extractor

In our 1975 Frankilin Arrow, we soon discovered that the standard Four Seasons roof hatches literally worked like radiating heaters on hot days. The square roof in the centre of the hatches consisted of 2 very thin sheets of aluminium with nothing but a sheet of cardboard in between them. The aluminium angle at the base of the hatch was totally un-insulated, the same went for the thin aluminium hatch flaps. The flaps were not such a problem if the hatches were open as they provided some shade and there was air between them an the fly screens. However, when running an air conditioner, they had to be shut, which meant that the hatch openings were covered by nothing but a thin sheet of aluminium in direct sunlight. on hot days, most of each hatch was actually too hot to touch, they worked literally like convection heaters, especially when closed with the air conditioner running. It was like running an air conditioner and 2 heaters simultaneously.

The solution was very simple, reasonably cheap and extremely effective. The first job was to insulate the roof of the hatch. I cut a sheet of foil backed, air pocketed insulation to size then covered that with a sheet of 5mm plywood, mounted on four timber spigots, using construction adhesive. The reduction in internal heat convection was immediate and significant, despite the fact that hot air rises. I then removed the the fly screens, which were an absolute pain. Not only did they block light through the openings, but also gathered a massive quantity of dust, which exacerbated the light problem. I cut some pieces of good quality perspex to fit the openings and fitted them permanently with contact adhesive and putty. They now work as skylights, letting in more that 50% more light than the fly screens. Best of all, the hatch covers can remain open whilst the air conditioner is operating. Light still gets in and the perspex windows are shaded by the open hatch covers. I covered the aluminium angle on the base of the hatches with insulation from the outside. The hatches are now as cool to touch as the rest of the ceiling, which is well insulated. The air conditioner is significantly more efficient. 

Even with such huge improvements, even more was possible by tackling air flow. Whilst hot air rises, it still needs to escape. That issue was tackled very easily by fitting small extractors into the roof of the hatches. I used solar powered units that have their own solar panel fitted on top. If going down this path, be sure to install the "night and day" models. These utilise a lithium battery that is charged by the mini solar panel and thus they can operate when not in full sun. They cost around $120 each. They extract a surprisingly high volume of warm air and are absolutely silent. They're also extremely effective in keeping a caravan cool whilst under tow. Since fitting the extractors, we have noticed how much cooler it is inside the van when we make roadside stops. The extractors are another marine product. We have found that products sourced from the world of yachting are not only cheaper, but more robust and effective than products designed specifically for caravans and RVs.

Our airflow was further improved by the installation of wall mounted cabin fans. They can also assist with the efficiency of the air conditioner. Being mounted at the rear of the caravan the air conditioner outlet provides a flow of air through the rear sleeping cabin, through to the front. The laws of physics determine that as air is blown further from the unit, it gets warmer, expands and rises. We use the bedroom fan to combat some of this effect. We simply run the fan across the flow of air at 90 degrees, angled upwards at about 35 degrees. This functions as an air curtain, keeping the flow of air from the air conditioner cool and preventing it from expanding and rising before it reaches the main cabin / kitchen area. It works very well indeed.

On the subject of fans, since installing wall mounted cabin fans, we have used the air conditioner more than 70% less than we previously did. This is where I turn into the 60 Plus Bearded Akubra Wearing man! "Don't buy anything other than Caframo fans. I've got Caframo fans. You can't camp here without Caframo fans. It's un-Australian!" Fuck it! If you can't beat 'em, join 'em.

I have to say, I haven't found a product that comes near to the Caframo fans. They are freakishly good. Their super lightweight blade design, not only makes them extremely efficient in terms of power, but also makes the absolute most of wind chill factor, generating a flow of cool air that generally negates the need for air conditioning except for in the most extreme conditions. What's particularly great about them is that they draw only 0.5 amps and can be run from even the smallest 12v house battery setup. 

Caframo Ultimate cabin fan

Carframo fans were originally designed for marine use and are used in yachts the world over. They're a very high quality product, fully manufactured in Canada, right down to the super efficient motors. As far as electric fans go, they're not particularly cheap, probably double the price of a cheap Chinese wall mounted fan, but 5 times more efficient, substantially quieter and significantly smaller. Where I do disagree with a lot of caravan and RV owners, is on the model. There are several models. The most popular by far is the Sirocco, which is also by far the most expensive, clocking in at around $180. When I researched the range extensively, I set out to buy the best model, regardless of price. I ended up buying the Ultimate, which clocks in at only $80.

 OK, so here's the run down. The Ultimate is more powerful than the Sirocco, but the high setting is a bit noisier than the Sirocco's highest setting. We generally use the ultimate on the lower setting, which is very quiet. We don't use it on the low setting because it's quiet, but because it's usually powerful enough when it's very hot, we use the high setting, but the noise doesn't bother us. The Sirocco has 3 speed settings, the ultimate has 2 - big deal. The Sirocco features a timer. I'm still attempting to work out what the benefits of that feature are. The Sirocco fan is mounted on a "gimball," which means it sits inside a moving ring and can be rotated in any direction. Seeing as you can buy 2 Ultimate fans for a fair bit less than 1 Sirocco (there are pair deals), that doesn't sell me on it. Finally the Sirocco has a protective cage around the blade, whereas the Ultimate doesn't. Given that the ultimate's blade weighs little more than a similarly sized piece of card board and the motor is clutched, the open blade is not a problem. If you are stupid enough to walk into it, something I do frequently, it doesn't hurt at all, but causes you to yell "oh fuck!" and give everyone else a bloody good laugh. 

Obviously from my perspective, given my penchant for tropical climes, cooling is a much bigger deal than heating. Cooling also presents greater mechanical challenges. However, as I have outlined, the mechanics of cooling can take various forms, however none of them are as efficient as they can be without first addressing the issues of shade and insulation. Not all caravans, particularly the more modern ones, have good front to rear airflow, which can work wonders in even the slightest breeze. for anyone who's attempting any kind of temperature control in an RV or caravan, it's important to establish where it's weak points are, our hatches being a classic example. If you can reduce the ambient temperature of your van or RVs interior prior to using appliances, the efficiency of the appliances that you use, will be that much better.