Measuring a pwm charge feed

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Measuring a pwm charge feed

Apr 8, 2008
Hi people
Need some advice

My Pod (aka a caravan essentially)
Has a solar pannel and a charge controller to the leisure battery on-board

Now its a 100watt pannel
Im getting a voltage increase on the battery - which would say that yes its charging

But when i pulled the fuse out and stick my multimeter or fuse current reader into it

Im getting a mere 8ma output

Not a 8ma output would take donkeys years to charge a battery
But its a pulsing 8ma charge (hence the pulse width modulator)

So something tells me the 8ma is possibly the lower pulse reading but my multimeter aint able to refresh fast enough

Any ideass on how i can read the actual charge rate?

As youtube videos ive watched are pretty lame....
could you throw a smoothing circuit on it

measure the input going into the charger
Last edited:
I meant try it on AC.

Depending on the meter some have a current limiter on the mA range but a fuse on the amp Range.

It could be it’s producing too much current for your meter at the mA level and like you say, you’ve blown the fuse on the A Range
So did a little more testing....
The pulsing detected is because the solar light detected warning/light is flashing

So covered up the solar pannel... the light stops flashing - i get a smooth 8ma draw....

Even with new fuse and on 10amp scale
Itll flash 00.01amps and flat line again....

So yea.... i dont think im charging
Found an interesting video about pwm solar chargers

They simply step the voltage down to charge the battery

However im geting on 9v from my pannel so the controller is shutting the flow off to orevent discharge

So me thinks my pannel has died

S130 is correct about True RMS meters. If it has a very low duty cycle you would have to use an oscilloscope. Try disconnecting the panel from the charger and connecting it to a 21W bulb (brake light bulb) and measure the voltage with that load. In bright light of course. It should be at least 13V for a good panel. This is assuming you have a simple PWM controller. The more complex controllers use a boost-buck converter that can produce 14V output with a lower input voltage.

Robert G8RPI.