Solar Panels - To Fold Or Not To Fold

Solar power generation is never a precise science due to a number of variables. Panel direction, latitude, time of day and cloud cover aside, there are a number of things the "off grid survivor" can do to ensure that they're getting the mos out of their solar array.

Most of us who live on the road, want the convenience of having our panels conveniently set up on the roof of our van or RV. It makes use of a surface that's otherwise there solely for the purpose of protecting us from the elements. It also means that we never have to set them up and that we can charge batteries whilst driving.

There is a fairly obvious downside to roof mounted panels and that's the direction they point.

Whilst a panel that's flat on it's back like a Welshman after the pub has closed, points neither north, east, south or west, it never faces the sun directly. Well, unless you're sat right on the equator.

In temperate latitudes and the lower tropics, meaning most of Australia, even at midday, the sun is never directly overhead. At risk of being called out for my anorak-like pedantry, I shall elaborate. At around 33 degrees south, somewhere in line with Sydney, a panel flat on its back in full sun at midday, will generate around 10 to 15% less power than the same panel tilted at a 45 degree angle, facing the sun. Either side of the sun passing the yard arm, the equation becomes more extreme. In fact flat panels are very inefficient outside of the hours between 10:00 and 14:00. 

I'm not about to take an angle grinder to the Sikaflex 252 that holds the mounting brackets to my roof. Everyone knows that shit will never come off. However, there are measures that can be taken. The ultimate is a mechanical mounting system that allows roof mounted panels to be tilted towards the sun at different times of the day. I don't think such mechanisms are far from coming to fruition in terms of caravans and RVs, but it will be quite a while until they are generally affordable.

I've opted for a somewhat more manual solution. I have a reliable 300 Watt array on the roof of the caravan. I don't charge the house batteries via the car's alternator, as i have another deep cycle battery system in the car that powers the Engel freezer. The solar panels on the roof ensure that the house batteries are topped up by the time we arrive at our destination. Sun permitting, of course. 

In addition to that we have a 160 Watt, portable folding panel that ties straight into a parallel connection to the roof mounted array, via Anderson plugs. It can also be tied into a separate solar regulator associated with the auxiliary battery in the car. 

I have to admit, the panel does take up space that roof mounted panels wouldn't otherwise take up. It can also be a bit of a pain in the arse to pack away and take out of the car. All that said and done, it's worth it for how much extra energy we can generate by pointing it towards the sun and moving it throughout the day. In fact, the 160 Watt folding array generates just slightly less energy than the 300 Watt roof mounted array when they are both in full sun, just either side of peak time. Earlier in the morning and later in the evening, the folding array generates considerably more energy.

Now your folding arrays, portable panels, whatever you want to call them, are an interesting topic. If you're interested in that kind of thing, that is. I'll use a 160 Watt array as an example. A) Because that's what I have and B) because it's about the biggest array you can use with a 10 amp regulator, which I suggest using if it's a stand alone system . If you want to buy a good one that works out of the box, you're looking at about $500 - $700. In fact, there are some being sold at a major camping franchise that cost that much and they're not even that good. 

For a cheap 160 Watt folding array from ebay, you're looking at about $220. Folding arrays come equipped with their own solar regulator and cabling to an Anderson plug. The regulators are allegedly the "MPPT" type, which is supposed to be good. The regulators on the cheapies are invariably shit! The regulators on the expensive ones are variably ordinary. However, the panels are of pretty much the same standard on either the cheap or pricey arrays. 

Now here's the "thing" as the kids say. You can buy a very good solar regulator to suit a 160 amp array, for around $70. The Vicrtron Blue PWM Pro 10 amp regulator is about as good as any small regulator you can buy. If you are using your folding array as a small system, just for a small compressor fridge, it's all you need. Remove the regulator that is fitted to your cheap folding array. Make sure to store it where it isn't a problem that it's not biodegradable (i suggest a fire) and fit the new regulator near to your battery, not on the panel. If you intend to add other panels and a bigger battery bank later, I suggest a 30 amp regulator, which costs about $150. The same applies if you are building a system from scratch with a mixture of roof mounted and portable (folding) panels.

Oh no!!! Here comes the over 60 bloke with a beard, wearing an Akubra!!

"You can't use that in this camp. It's a PWM regulator! I don't have one of those. I have an MPPT type regulator. You have to have one like mine or else you can't be a real Aussie. That's just un-Australian!"

Well, as can often be the case, Bearded 60 Plus Akubra Bloke is talking out of his "medjool." Without going into the finer points of differences between PWM and MPPT, I'll just say that MPPT regulators are only going to help if the array is greater than 600 Watts.  If you would like to read some sciencey stuff from a company that makes both: Here's a Link: 

https://www.victronenergy.com/blog/2014/07/21/which-solar-charge-controller-pwm-or-mppt/

Even better than really good regulators being quite inexpensive, is the fact that if you are adding the folding array to an existing system, you probably won't need another regulator as it's likely that the one you have is sufficient to handle an addition to the array. You will just need to fit a parallel connection to the existing array, terminated with an anderson plug. You can just plug the folding array into the existing system.

But wait! There's more! More slightly shitty stuff unfortunately, but it's no big deal. The cables on cheap folding arrays are also invariably shit! They're very, very narrow. Bearded Over 60 Akubra Man probably likes to piss in the bush. He'll tell you, the more you squeeze on the plumbing, the narrower the aperture gets and  the bigger the build up at the pumping station. Unfortunately there's considerably less action at the nozzle. Plus he'll probably need to see a doctor with a very small camera. Electrons and cables work in much the same manner. 

When I purchased my 160 Watt folding array I tested it in full sun. I measured 3 amps at the end of the cable, when it should have been around 8 amps. I removed the "MPPT" regulator and stored it in the wheelie bin and measured it again with the cable attached directly to the panel's connections. I measured a whopping 3.5 amps. Something was well and truly squeezing on the plumbing. I stored the cable with the regulator and measured approximately 8 amps at the back of the panel.

Why would you even allow that to happen. Australian importers are bringing these things in and not even testing them. For the sake of not fitting ten bucks worth of new cable, which they could very easily add to the price, they're putting a product out there that's shit by default. We live in a very lazy society where capitalism determines that business is about doing as little as possible in return for optimised profits. 

Anyway, the panels, the most expensive part of the system are excellent. So, I fitted a new regulator for $70. Seven metres of 6mm twin and an Anderson plug cost me $30. Add that to the cost of the folding array and I had a total of $320. Tools required, one screwdriver and a crimper for the Anderson plug. I now have as good a folding array with a very good solar regulator for my Land Rover auxiliary deep cycle battery for half of what a "high end" folding array would cost. When is isn't charging the Landy Auxiliary, it plugs straight into a parallel connection with the roof mounted array. 

This is all pretty simple stuff, but I have a background in fairly technical stuff. Don't worry if it sounds like Wolof. If you comment or message me via the blog. I'm happy to provide a breakdown of this information and any more information that you might need. Just don't look like you don't know what you're doing with Bearded 60 Plus Akubra Bloke around. He lurks in campsites, waiting to pounce on anyone who looks like they need to be told what to do or buy!