Solar panels for camping - squeezing out the most power

Posted on 15 Mar 2021 by

I've been doing some testing this week, comparing the performance of a cheap folding panel kit with a premium kit. The results are interesting!

We sell premium kits, in the certain knowledge that people can go to a supermarket or car discount store and buy something that purports to be the same for, maybe, half the cost. Why do we only sell the premium ones? Read on:

I've been scouting the supermarkets and I found a budget 160w folding solar panel kit that seemed to be very close, in theory, to the 160w kit that we sell. 

  • The actual glass panels looked very similar
  • The premium kit had much better framing and catches, a better stand system, a stronger bag, and a 20amp pwm regulator. (PWM? I'll explain later.)
  • The budget kit all worked, but it came with a 10amp regulator, which is BAD!

What's wrong with a 10amp regulator? Nothing - on a panel kit up to about 120watts, but a 160w panel kit can send about 90% of that out of the regulator on a sunny day, ie about 144watts which, at a 13.4volt charging rate, is 10.74amps - ie more than the regulator is designed to handle. 

What does that mean? Probably nothing most of the time but in perfect conditions, on a really sunny day, with a fairly full battery, the regulator would be faced with carrying more current than it should, which means heat, burned out components or, more worryingly, a fire.

Nobody wants a surprise electrical fire on their campsite, least of all when they are out bushwalking, but let's ignore that, just for now. 

We checked the output of both kits and they were pretty similar. The premium kit might have had the edge, but the gap was modest. We tried swapping the batteries that they were charging, then swapping the regulators from panel to panel, and the results were still pretty consistent. The budget kit's wiring was skinny, which would affect performance if the extension leads were used, but didn't make much difference if the panels were a metre from the battery (they won't be that close on a campsite because panels like sun and tents and campers like shade).

Then we decided to see what impact a top quality regulator would make, so we put in one from a company that makes really nice gear - a Victron BlueSolar 75/15 (can take up to 75volts in, and handle up to 15amps out). This is an MPPT regulator - maximum power point tracking - which means that the smarts inside it are checking the power coming in and doing some jiggery-pokery to squeeze the most out of the panels, and this was the interesting thing - output went up more than 20%. A PWM regulator (pulse width modulation) is old technology, cheap to make, functional, but limited.

So, PWM vs MPPT - more than 20% gain? That's huge, and well worth the effort of changing the regulator. The commonly used term is "more than 10% gain" and our results supported this.

So we checked a few times and, as the cloud and sun conditions changed, the results were broadly the same. The Victron MPPT regulator was having a field-day, and so was the battery.

I won't bore you with lots of data, but here are my conclusions:

  • The premium panel kit is built better. It will last longer and, with its better cabling, will be more reliable out on the campsite, where it belongs (see footnote below)
  • The cheaper panel kit works, pretty well, for the money, but this is a day 1 test, fresh out of the box. On close inspection,the panels are not as strongly made, the internal connections are thinner and I have no doubt that this would be a throw-away in 2 or 3 years. If i was going to rely on it, I'd spend some money on a much better extension lead to overcome the cheap/skinny cables that the manufacturer had used, and...
  • ...the use of a 10amp regulator in the cheaper panel is inexcusable. It's wrong, plain and simple, and risky, and the supermarket and their suppliers in China should be ashamed of themselves - but we know how that story goes
  • Changing up the regulator on either kit is a no-brainer. Legitimate versions of the MPPT regulator that we tested sell for about $150, sometimes less (RRP is $165). This one has plenty of battery-type options, so it won't cook your battery, it can handle lithium batteries, which is where the deep cycle market is heading and, because it is from a high-end manufacturer, it really is MPPT (plenty of regulators from dodgy manufacturers and dodgier websites say MPPT on them, but aren't!).

I'm going to test the cheaper folding kit through a number of trips to see how it hangs together. I already know that the premium kit does well because we get plenty of positive feedback, and the camping scene is littered with people drinking warm beer on their holidays because they saved $200 on their folding panel. Odd way to spoil a holiday, but each to his own! 

So, we sell the premium product because I don't want my customers to drink warm beer (unless they are Pommies, and like that sort of thing).

What this test has shown is, without a doubt, a quality regulator can extract more power.

And that has to be a good thing.


Footnote - I tested the cheaper folding kit on a 4 day camping trip. It rained for 3 of the 4 days and the hinges and catches on the panels went rusty. Still usable, but pretty poor, and I'd have to say "not fit for purpose". Did I hear anyone saying "you get what you pay for"?