Solar panel query.

patman99

Not quite sure where to post this, but here goes.

I have a 12volt/12watt solar panel (the sort that has three different leads that can be plugged-in to allow you charge your car via cigar lighter, direct to the battery via crocodile clips or by hard-wiring). Measured it today and it shows as generating 27volts. !!!!!! is going on?.
I dare not use it to keep the car battery charged whilst it sits on the drive up for sale as I don't want to fry the battery.

espresso

You are measuring the open circuit voltage. The quoted 12W will be the maximum output power and a charge of less than 1A will not fry your car battery. Measure the current flowing when it is connected to the battery.

patman99

I was measuring the voltage, not the wattage.
I have used the same multimeter on it before and got 11.6 volts. Admittedly this was under indoor lighting rather than in the sun, but was not expecting such a high reading.

espresso

patman99 wrote: »

Not quite sure where to post this, but here goes.

I have a 12volt/12watt solar panel (the sort that has three different leads that can be plugged-in to allow you charge your car via cigar lighter, direct to the battery via crocodile clips or by hard-wiring). Measured it today and it shows as generating 27volts. !!!!!! is going on?.
I dare not use it to keep the car battery charged whilst it sits on the drive up for sale as I don't want to fry the battery.

patman99 wrote: »

I was measuring the voltage, not the wattage.
I have used the same multimeter on it before and got 11.6 volts. Admittedly this was under indoor lighting rather than in the sun, but was not expecting such a high reading.

Yes I can read.

A multi-meter in inexperienced hands is pointless!

Measure the current flowing when it is connected to the battery - you may be lucky to get 500mA charge current!

patman99

Hooked-up the panel and it worked as it should. No fried wiring in the car.

500mA would be a good charge rate anyway. When you consider watts/volts=amps, with a 12V panel rated at 12watts, the max ampage would only be 1 amp anyway, so no chance of blowing a fuse.