Easy way to measure solar output (Amps)?

[rexlion]

I tried measuring the circuit between my solar panel and the controller today, but couldn't get a reading. I was wondering, should a digital multimeter (I have a Fluke 115) be able to read small amounts of current like 2 or 3 amps? My panel should put out a max of 4A in bright sun, but I would like to see what the actual output is in a variety of conditions (bright haze, cloudy, etc).

Has anyone done this or have ideas on an easy way to do it? Will a clamp meter (TRMS) do the job?

I know the system is functioning, because I can measure the voltage inside the trailer (in a 12V socket) and it goes to 14.14V when the panel is hooked up.

[MEXICOWANDERER]

May I recommend a PERMANENT meter?

20-amp digital meters and shunts are very inexpensive, and not difficult to install in the solar controller wire. This way you know what the panels are doing for a living.

[rexlion]

I did all of the above. I am getting "something" but it's not right.

[SteveAE]

Hi,

The battery terminals need to stay connected and you need to open the circuit (you can accomplish this by removing one battery terminal if you wish). Then your meter goes where you opened up the circuit (i.e.; if you removed one battery cable, then the meter will connect between that battery terminal and the cable that you removed from it).
Don't forget to set your meter to DC Amps and, most likely, you will have to move the red test lead to a different jack on the meter....to something that says something like "Amps"
If you don't get something when doing the above, maybe the fuse inside your multi-meter is open. Should be easy enough to replace.

Steve

[rexlion]

Ok, I tried taking the positive cable off the battery and measuring across there. The meter will very briefly say an amp or two, then the numbers dance wildly for perhaps two seconds, and it settles down to about .1A. Doesn't matter if the panel is in full sun or in shade, same thing happens. I'm not sure how to interpret that. I do have it set for dc, not ac.

The controller 'sees' the battery condition and charges accordingly. I wonder if my Morningstar Sunguard SG-4 sees the meter in the circuit and thinks it's supposed to go into float mode?

[Roadpilot]

The Fluke 115 should be able to measure dc current. The probes have to go from the A(amp) input to Com and the internal fuse must be intact. It's good for 10 amp and 20 amps for 30 seconds.

Most inexpensive clamp on current probes only measure AC current. You'll need a more expensive DC clamp on current probe.

But your Fluke should do it.

[BFL13]

I take the amps between the controller and battery, not from the array side of the controller.

For under 10a, you can just put your multimeter pos and neg as part of either the pos or neg controller to battery wire and read the amps. You will want alligator clips on the meter leads because you only have two hands!

Some multimeters instructions don't want you to leave it on amps more than a few seconds, so with them you can't leave it hooked up as a gauge you can keep watching. For that you can go on ebay and see a zillion cheap little ammeters you can get that work ok too.