[chbot] PWM solar charge controllers

[Robin Gilks]

> Good evening all
>
> I have a quick question about PWM solar charge controller.  I recently
> bought a 12V 200W solar panel kit from Jaycar, with a built-in PWM charge
> controller.  In full sunlight it's putting 18V across my 12V gel cell
> (albeit a PWM signal at ~250Hz) which seems a bit high.
>
> From my understanding the charging voltage for a gel cell is supposed to
> be
> about 14.4 to 15.0V - do I risk cooking my battery by connecting it to
> these panels, or being that it is PWM (so average voltage is less than
> peak) is this normal operation?

If you are measuring 18v with the battery connected then it's already too
late, the battery has had it - if that is the open circuit voltage then
that is what I'd expect for a panel designed to charge a 12v battery.

Another way to check is to keep the voltmeter on the battery and
disconnect the charger - if it is really at 18v then it will hang at that
voltage and then drop away over a few seconds.

I suspect its an artifact of the meter. If you know someone with an old
analog AVO meter or similar, that is more likely to give a more accurate
reading. You might be able to find a car voltage gauge at a scrappy that
would be useful.


-- 
Robin Gilks