PV Gap

Eddie Said:

I want to use my car solar recharger to power some lighting.?

We Answered:

The principle of this idea works, but in practice it may not be a good idea. Why?
1) Your solar panel will only charge your battery during the day, and there is a limit to how much you can charge a car battery. In theory, your car battery should be "full" from driving.
2) So let's say you want to run just one 60 Watt light bulb (!) during the night (assume 10 hours): you will then draw from your car battery 50Amp/hours overnight.
This is as much as you would leave your head lights on over night, your car will most likely not start in the morning.
3) Now you need to replace that "lost" charge with your solar cell during the day. That means your solar cell needs to put the same amount back into the battery, i.e. it must be a 12 Volt 60 Watt solar cell. Can yours?! We are talking about a $300.-- cell. And at this level of charge-power, you would also need a charge controller (another $100.-).
4) Finally, a typical car battery doesn't "like" to be discharged below 80% of its capacity frequently, it will age very fast. For this kind of job you would need a so-called "deep cycle" battery (and that is what they are using in "proper" solar power installations).
All the above presumes that your "Night Light" runs at 12 Volt DC. If you want to operate a 110 or 220 Volt light, you also need an inverter, and its efficiency is about 80% only, meaning you loose 20% of battery power to heat dissipation.
If you use a standalone car battery (without it being inside a car), then items 3) & 4) above still apply.
Good idea? You be the judge....