Windscreen Solar Charger

[paul1763]

I've just connected a multimeter to an old solar charger that you put in the windscreen and its jumping all over the place between 18 and 20 volts, is this too higher voltage to connect to a car battery? Thanks for any advice

[Old_Geezer]

That would be under no load. Under load it may drop considerably.

One can charge a car battery from a windscreen solar cell ? How long does that take ?

[Hymie]

The idea of these solar chargers is that they maintain the battery charge state when the vehicle is left unused for a prolonged period – it would take many days, if not weeks to charge a flat battery using one.

I have never used one, but if connected via the cigarette lighter socket – then the socket must be powered with the ignition off (otherwise it won’t charge the battery).

[douglas9401]

I don't care what anybody says, I'm not going to put a hole in my garage roof to keep my battery topped up.

[paul1763]

Thanks all for your answers, I'm only using it to keep one of my tractor batteries topped up as I may use it every day one week and then may not start it for 3 months and its wiring system is not the best and totally drains the battery occasionally