How long does it take a 5 watt, 2 volt solar panel to charge a 2 volt R.V. battery?
depends on the sunlight. And on the size of the battery. But it may never charge, as you need at least 5 volts to charge a 2 volt battery. So unless the sunlight is bright enough to generate 5 volts, all you will do is discharge the battery through the solar panel. But a large battery is 00 amp hours of capacity. Even if you had a 5 volt 5 watt panel, that generates only amp at most, so it would take over 00 hours to charge that size battery. .
Most solar panels have something called a charge controller on them. This prevents electricity from going backwards from the battery to the panel. Solar panels are rated at 2V but they do put out a little more than that during full sun operation. You didn't specify the size of your battery but it really doesn't matter. It comes down to your consumption of power. If you are only charging the RV battery so it maintains a charge when you don't use it very much, a 5 watt panel is fine. It will charge the battery and keep the small drains on the battery from making it go dead ( the clock radio, the theft deterrent system, etc use power even when RV is off) But if you are using the battery to run things when you are parked, you probably don't have a big enough panel. If you use a 30watt fluorescent light and a 00 watt laptop, you need 30 watts of power saved up every hour in your battery and that's with no inefficiencies. So if your panel puts out 5 watts an hour and you are using 30 watts an hour, you need 30 watts/ 5 watts = 9 hours minimum of charge time to run your stuff for just one hour. You probably need a panel of around a 00 watts to get any meaningful use of your battery. Plus, you never want to run your battery to full drain because it ruins the plates inside the battery. Watts = volts x amps. If you have 2 volts panels, you would charge at 8 amps with a 00 watt panel. This is a good charge rate. Any more than this and you risk warping the plates with too much heat.
It is related to the size and capacity of your battery.
