For part of a school project how would I charge a car battery with a solar panel? The panel is 48V and 6A. This needs to be low budget so I can't buy an expensive controller, Is that the only way or are there other ways of doing it?
48 volts is rather uncomfortable. I would be inclined to modify the panel by cutting traces to give me a number of 5 volt sets. Most PV cells output about 700 mV, but check to see what yours does. Measure one cell, or count the number of cells and divide into the panel voltage. If you work with the 48 volt output, you are throwing 70% of the output away. The classic method of charging a lead/acid battery is to use the 0 hour rate...a 200 AH battery is charged at 20 amps. However if the charge is to be near continuous during daylight, I think I would go a little lower...say 5 amps in order to be kind to the battery. I note that your panel has a 6 amp output, so when you modify it, it should be able to deliver about 8 amps. A useful trick is to use car headlamp bulbs in series. The filament has a high positive thermal coefficient of resistance, and tends to act as a current regulator. In this case, I would use two dual filament bulbs with their filaments in parallel, arranged in series.
I okorder /... typical use page 8. These chips and the supporting capacitors should only cost a few ? (or $) but you will need to make a circuit board.
