I have been mightily puzzled over the last few weeks by the performance of my solar system. Not so much puzzled by rather concerned. Ages ago, my solar ventilation system was very simple. Two CPU fans connected directly to two solar panels. In strong sun they shifted a lot of air. In weak sun they barely buzzed. Thinking of storing power to use to run the fan, I employed a cheap Chinese charge controller and a 5AH Radio Shack battery. It worked well. The fans would run happily for hours on end in bright sun. In cloudier conditions the fans would still go.
Then I decided to upgrade to a more powerful fan to shift even more air. I upgraded the battery to a 10AH battery that I got on eBay for $20. Initially I was getting 10 minute bursts on the fan between recharging periods. Eventually after a week or so I was getting 10 second bursts with very brief charging times. That was pretty weird!
At the same time as I was getting odd performance I found the maximum voltage of the battery had dropped. That was very weird too. I was using sealed lead acid batteries and not knowingly over-rating them. I was also getting a warning triangle on the display of my charge controller. Looking it up online, it seems most charge controllers from China use it to indicate a battery or a device fault. I disconnected the fan and it remained displayed. Clearly it was a battery fault.
I'm getting the feeling this charge controller could be turning into a battery killer. I tried it again today with a pair of 7AH batteries purchased in Radio Shack's going out of business sale. That's a total of 14AH which at 50% use should run a 2.5A fan for between 2 and 3 hours. The first time I tried it today, the battery voltage reached 13v and the fan ran for two minutes. After that, it ran for 10 seconds or so each time. That was about what the 10AH battery was doing too.
I don't want to point the finger of accusation at the charge controller but it's looking very much like the charge controller is the problem. I have several other Chinese charge controllers but it seems to me that they're unusable. The highest voltage at which they will stop taking charge out of a battery is 11.3V which is way too low. I understand a battery should not be depleted more than 11.9v without damaging the battery.
In a fit of exasperation I ordered a charge controller yesterday. It's another like the one I ordered that arrived broken. I believe it's coming from California but was made in China. I regret buying that now even though it has not yet arrived.
In communication with Eric, he pointed out that if I bought a USA made charge controller, even though it would be more expensive, I'd save money and hassle over buying large quantities of Chinese junk. He's absolutely right. The price of an equivalent Harbor Freight controller is quite pricy at $80 but on the other hand I have 2 unusable controllers, one broken controller and one that seems faulty plus one I just ordered and at about $10 apiece I've already spent $50 or most of the price of a Harbor Freight controller. I can't return any of the Chinese stuff whereas I can walk into Harbor Freight and shove the offending object under the manager's nose.
Having spent $55 on a $68 battery from Harbor Freight, I'm now rather wary of letting it anywhere near my Chinese controllers given their apparent penchant for destroying batteries. I have a feeling that I might just put the Chinese stuff in a box and just go and get the expensive Harbor Freight controller. I'd rather not risk an expensive battery to the vaguaries of dubious Chinese stuff that comes with either no instructions or at best semi-literate instructions. To be honest, the best Chinese instructions look like they have been whacked through Google's rather dubious online translator. It reminds me of the automatic translation of "The spirit is strong but the flesh is weak" which was translated as "The meat is bad but the vodka is strong".
If I install the new charge controller, I have a feeling I will most likely install it in the front of the bus and run the fan off my 15W panel rather than my two 10W panels - for the moment. Moving it to the front has many advantages. I'll have to install an additional power cable for the back solar panels to bring their output to the front at some future point. Running off the front panel for the moment will also likely be the galley circulation fan - since the wiring is easily accessible.
As can be seen, there's plenty that needs doing under the bus in terms of wiring. All will have to wait til the weather gets cold enough to force the antisocial critters such as spiders, ants and mosquitoes into hibernation. If it's another warm winter, after I've retitled the bus I'll drive North if I have t in order to work in safety.