Probably a bit of a thicky question but...

harryajh said:

Hi, firstly appologies if my terminology is wrong but I know very little about electrics and have no idea why this is happening -

I have 2 portable solar panels (I use for charging a Motorhome Battery), when I test them with an amp meter I get different results.

So,

From Amp Meter to Solar Panel 1 gives 240s milliamps when
Red -> Red
Black -> Black

From Amp Meter to Solar Panel 2 gives -240 milliamps when
Red -> Red
Black -> Black

why is it negative?, does this mean if I connect both to the battery, what SP1 puts in, SP2 takes out?

But from Amp Meter to Solar Panel 2 gives 240 milliamps when
Red -> Black
Black -> Red

so should I connect SP2 Red to Black and Black to Red?

Thanks in advance
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SparkyChick said:

If you're using a current measuring mode on that multimeter, I'd say you're quite lucky not to have destroyed it... probably the panels can't provide enough power to do any damage.

The measurement you should be using is voltage. Specifically DC volts, most likely the 20 range. Then you would expect red to be positive and black to be negative (assuming you have the red/black leads connected to the correct inputs on the multimeter), in which case if you connect the red croc clip to the red lead etc. you should see a positive value. To be certain then you can reverse the connections and you should see a negative value. For certainty, you could try measuring the voltage across say a small battery just to prove the meter is working as expected.

Without being there it's hard to provide any more concrete advice.

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mainline said:

Connect the negative lead from the solar panel to the negative lead of the battery, and use the 10amp DCA range of the multimeter in series with the solar panel and battery.

The red lead on the multimeter has to move to the 10amp socket, don't forget to move it back for any other measurements apart from current.

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