Working out the kinks

Charge controllers are supposed to do two things: To charge a battery unit it is full and no more and to permit discharge of a battery until it is at the point of maximum safe discharge. That’s a very narrow range between 12.7/12.8v and 11.9v. I’m never sure with my LED charge controller just whether I’ve got there. The LCD charge controller used to tell me that. I suspect the LED controller is cutting out way before the battery is full. In short I am singularly unimpressed by the charge controllers I’ve had so far.

I had a good 10A controller that was LCD and didn’t worry about my fans starting. The only problem was I blew it up. The rest have been a catalogue of woes. Reading what is said on the various solar websites, the’re all claiming there’s no point in a solar system less than 200W. I beg to differ. My system works just fine. The problem is that the charge controllers are singularly useless.

I switched my fans onto automatic and left them running for 5 minutes on the hour every hour from 10AM until I went to the bus at 4pm. By 4pm the charge level had dropped tremendously. In fact the fan started at 4pm and the voltage steadily dropped over the two minutes before I stopped the fan from 13.4v to 10.9v when the lights started flashing on and off. I could hear the power of the motor dropping way before that.

Given that I didn’t use the power much at all yesterday, the batteries should have been pretty well fully charged. The door control only uses 160ma apparently. The mystery is still what’s happening. It has been plenty light and the battery is a deep cycle battery and is only 18 months old. The fans will have used 5A between them for a grand total of 35 minutes or around 2-3AH. The battery is 35AH which means that even if there had been no sun at all, I’d still have used at maximum, 1/7th of the batteries capacity. Even allowing for the 160ma of the door controller that’s still just 1.6AH over 10 hours. Even at 1/6th of the battery being used there still should be more power left than it took to power the fans for 5 minutes just now. This is a total mystery and I’m going to have to say (I know there’re no current leaks because I know how I did the wiring) that it’s going to be either the charge controller or the battery that’s at fault with my money being on the charge controller. With a full battery and 5A usage I should have had at least 3 hours out of those fans before they stopped.

My second Hopkins to cigarette lighter adaptor still has not arrived from New York. According to the post office records it’s still there. Heaven alone knows why. I’m sure that if it had drugs in the shipment I’d have had a nice little visit from somebody by now. I can’t fathom why it has been stuck in New York for the last week. Thus I looked at my supplies and found I have more Hopkins adaptors. Thus I made a Hopkins splitter. This allowed me to plug both 30W solar panels in simultaneously. Currently then I have 5 solar panels interconnected for a total of 95W.

After I’d done that, I realised I’d blundered earlier. When I made the dual cigarette lighter plan, I. Should have realised that I could have run a single cord and had the Y connection close to the panels instead of  way away from them. That would have probably eliminated the need for an extra input at the back. Still who said I know what I’m doing? I’m working all this out as I go along! As it so happened I have enough leftover Hopkins connectors to be able to  convert both cables into an extendable single cable. That should work well. Had I found before I went for a cigarette lighter input, the SAE/Hopkins 2 pin terminals then I’d have got a few.

I put the infamous watt meter back on my panels - the twin 30W panels that is. Now I know how much extra power I’m generating. Heaven knows how accurate the watt meter is. That’s one of the problems I just don’t know how accurate any of these tools or measurements actually is. It’s like tyre pressure gauges. Try to get two of them to agree!

There, for the first time in recorded history are my two 30W panels side by side. What I have mounted permanently on the bus is fine for most of the year. I don’t need to use ventilation as much in the winter as in the summer. Thus there’s no point in permanently mounting more panels. In any case my reservation on mounting stuff on the roof is based on years of driving schoolbusses and encountering low hanging branches. It’s just not possible to see a lot of them either.

That’s my fancy cigarette lighter splitter. Had I used the Hopkins splitter then I wouldn’t be waiting for things to arrive!

As far as the charge controller is concerned, this pulsing nonsense when the battery gets too low is just sheer nonsense. It’s as much nonsense as the other charge controller going bananas when the fans go on.

I’m still at a loss to know exactly how a PWM charge controller is better than using a straightforward cut-out circuit that cuts out when the battery is full and just connecting the panels direct via that. As far as automatically cutting out when the battery hasn’t enough charge in it - that’s a whole load of nonsense. None of my charge controllers seem to do that properly. The LED version just pulses the power while the LCD version just waves its hands in the air futilely. As far as the LCD version having multiple settings, that’s a total load of baloney. It has settings that make you feel good about setting them. Whether they’re more than window dressing with no actual effect is open to conjecture. I rather suspect they don’t actually do anything but rather make the user feel as though they have done something.

My pal in France suggested I used a German or Danish charge controller as he doesn’t think much of any of the other varieties. He recommended Xantrex as a good manufacturer. Looking at the prices I almost fainted. Thus I looked at MPPT controllers instead of PWM. If you’re going to get expensive they you might as well get something worthwhile! Then I found worthwhile meant paying $500!

My next step was to look on Amazon. eBay is fine for cheap stuff up to $20 but once you go over that, it’s not worth the risk. Amazon can be a bit the same way which is why I usually end up ordering from Walmart. It’s so nice to have a counter you can go to to return things.

Looking at the costs I’m wondering whether a mode cost-effective solution would be just to wire the portable solar panels directly to the fans and leave the charge controller alone and let that handle things that the system was designed for - lighting and cell phone charging. Those with very long memories will recall that originally I had two CPU fans running from my two 10W solar panels. I had no battery and the world was excellent. That worked very well though it took forever to change the air in the bus.

There is a very basic charge controller. I suspect it’s what you’d call a linear controller for about $8. I gather that connects the panels directly to the battery to avoid faffing about. It costs off the panels when the battery is full and presumably cuts off the circuits when the voltage is too low. Nice and simple!

Anyway, it turned out the cheapest Xantrex 40A controller was $500. I’m not sure whether the amperage means input amps from the panels or output amps from the battery. In fact, it’s getting to the point where I’m just thinking of wiring directly to the battery and putting an over-voltage cutout circuit from a car. Then just pressing the button to check voltage occasionally! This fancy electronics just doesn’t work and costs too much.