I've just fitted another
solar panel a few hours ago. My thinking behind the decision might be at odds with people with more knowledge than me but at least my thoughts are based on experience.
When we started using satellite television in our van about five years ago I thought it prudent to fit a panel. So I did -a 75 Watt Panel which I monitored as best I could. The panel would deliver about 4 amps on a reasonable day maybe five on very good day, and even on an overcast day would produce two or three amps. I delivered this to the batteries, the same sort of capacity as yours, through a 6 amp regulator.
I monitored the usage as best I could but the only guide I had was to measure the voltage and watch a red light which would start to flash on the regulator. When I became alarmed that the voltage would drop to about 11 volts I would just switch the television off. Usually the red light would then stop flashing, turn to green and there would be requests to turn the TV back on.
The television, lately an LCD television, and satellite decoder use about 8 amps. The 75 watt panel would provide about three, maybe four hours after a good day, television before I used to get worried. My partner likes her Eastenders and so on so I have to find a reliable way to get the fix she needs. In Britain this summer, using terrestial television (so just about 4 amps) I had no need to bother about over-consumption at all. The red light never flashed no matter how long we watched.
So today I fitted another panel, wired it in parallel to the old panel and I now have a total of 140 watts which should provide about 8 amps - you divide the wattage by 17. I don't know why. Ohms Law tells me you should divide it by 12 but probably dividing by 17 takes into account inefficiencies in the panel and installation. My maybe muddled thinking says that there's no point in producing a load of electricity if you can't store it so, after trying the panel for a while, I'll probably buy another similar high capacity
battery to the two I already have. If I think I need it, that is.
I also now have a new 10 amp regulator which tells me all sort of things that will probably prove useful to me. It tells me State of Charge which is probably more reliable that the straightforward voltage reading that I'm used to. I don't know how it works out the state of charge. I think it balances what you get in against what you use. It tells me how many amps the panels are producing and how many of those amps are being delivered to the batteries. Oh, and it also tells me the
battery voltage.
It also measure how much you get in a day and how much you use in a day. I mean that must be useful, yes? If you get more than you use Mr Micawber is happy but if you use more than you get then we are all gong to be unhappy.
The panels are easy to fit if you're fairly handy. I built a fairly rudimentary junction box the better to understand the wiring and also to make sure that everything was fused and protected. I've also labelled everything in the sure and certain knowledge that I'll have forgotten how I wired everything in six months time.
I very much don't regret buying the first panel and I don't think I will regret buying this latest one. In fact I don't see how we could live for reasonable lengths of time without a supplementary source of electricity. Maybe for weekends or so but not for two or three months away.
I hope it all works as well for you as it has done for us. I think you just have to look for the best price. If they look well constructed and buy from somebody reliable then everything should be ok. It's not like there are any moving parts to wear out. Our latest panel is a Kyocera, I don't know about the first one we bought but we used the same supplier so amybe the same make.
Tom
