ashaughnessy Posted September 25, 2001 Share Posted September 25, 2001 I've just bought a little toy, a solar panel for trickle charging the battery. Stick it on the garage roof and connect it to the battery whenever the car is not in use and it's supposed to keep the battery up to charge. Now, am I right in thinking that it will only charge the battery if the voltage supplied by the charger is greater than the voltage supplied by the battery? In other words, the charger will have to be giving out 12 volts to be doing any good? If the charger gives out less than the battery, it won't be able to push any electrons into the battery against the battery's voltage. On a dull day it was only giving out 3 volts. I can believe it will give out 12 volts on a nice sunny day in full sunshine, but how many of them do we get in winter? Anthony Link to comment Share on other sites More sharing options...
Mike Bees Posted September 25, 2001 Share Posted September 25, 2001 Correct, if the panel is producing less than 12v then it isn't going to charge the battery. In fact it might drain it - use an ammeter to check if there is any current flowing when the panel isn't seeing light. Mike Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted September 25, 2001 Share Posted September 25, 2001 Well alternators are set to produce approx. 13.8 volts which is seen as a reasonable figure to keep a working battery up to scratch. That 3 volts would charge a 700Mah 'pencell' size NiCad. Great!!! Link to comment Share on other sites More sharing options...
ashaughnessy Posted September 26, 2001 Author Share Posted September 26, 2001 I've now developed a theory. The solar charger doesn't actually charge the battery! It connects in parallel and is (according to my theory) designed to supply current directly to electronic devices that operate when the car is sitting still (immobiliser, etc). If you don't have any electronics, then the charger isn't much use. If I lived in the sahara, maybe the charger would develop enough voltage to actually charge the battery but the problem would then be that it might overcharge, as it doesn't have any circuitry to stop charging when the battery is at full charge. So, it's mostly designed for modern cars with lots of flashing lights and not simple cars like mine. Anthony Link to comment Share on other sites More sharing options...
Mike Bees Posted September 26, 2001 Share Posted September 26, 2001 If you connect a 12v source and (e.g.) a 6v source in parallel then the 6v source ain't gonna supply no current to nuthin'... Mike Link to comment Share on other sites More sharing options...
ashaughnessy Posted September 26, 2001 Author Share Posted September 26, 2001 Stupid me! I never was any good with electrics, despite having a degree in physics! Link to comment Share on other sites More sharing options...
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