[chbot] PWM solar charge controllers

[Trevor Wignall]

How are you measuring the voltage across the gel cell? If you are using a
standard voltmeter on a DC range, then you are already looking at the
average, and 18V would seem to be far too high. If you are using a scope,
what is the minimum voltage?
Is the solar charge controller intended for 12 Volt lead-acid systems? Or a
higher voltage battery system?
What current is flowing at 18V? It may be your battery pack is very
discharged and the 18V is a trickle charge to try to get some conductivity
in the battery.
Another possibility is that your gel cell is much smaller than the charge
controller is designed for. After all, 200W at 14V is around 14 Amperes. I
would be uncomfortable using that on a battery much less than 70
Ampere-Hours (5C).
Cheers
Trevor

On Tue, Nov 19, 2019 at 9:41 PM Matthew Bridle <mnbridle at gmail.com> wrote:

> 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?
>
>
>
> Thanks for your help!
> Matthew
>
> --
> Matthew Bridle
> Github: @mnbridle
> Amateur radio: ZL2MNB
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