How To Meter A Panel's Output?

Lexicon7

Hi Guys, I'm puzzling over upgrading and "existing" system that came with my Lance Camper. I have one small panel but have learned that before doing much else such as adding another panel, I need to get a good reading on what the existing panel is putting out. It appears to be cranking but I have yet to Hydrometer the batt and will be doing that today. I'm planning booning it so want a realiable system for my solo and menial AH use.

The Panel is 51" X 13". Of course, the feed goes down through the fridge vent but I have yet to delve into how to work in that area of the camper. I assume I would get the best possible meter at the panel but I'll need to remove the vent cover and see what I have under there which I have also yet to do. I don't see a junction box up there but not surprised as the system may not have been assembled by "experts" shall we say. I am thinking I should be able to get a reading on the "Array" side of the Controller Terminals. Is this correct?
Also, how to use my meter: Should I use the V- with the 3 dots under the dash "side" or the V~ side?
Any responses greatly appreciated .:D

Cariboocoot

Re: How To Meter A Panel's Output?

I can't advise you on how to use your meter because I don't know what meter you've got and they're not all the same. If you haven't got a manual for it, get one with a manual. Very important to know how to use your meter; it can prevent burning it up, for example.

Things you can check fairly easily on your existing panel: Voc and Isc. From those two you can extrapolate Vmp and Imp - which are the important ratings for knowing power and adding panels.

For Voc disconnect the input from the charge controller and take a Voltage reading. It will probably be in the low 20's. Vmp is likely in the 17-18 range.

For Isc you need full illumination of the panel. The meter needs to be set to DC Amps and able to read at least 10 Amps (that is the limit on most DMM's). You connect the leads the same as with Voc, only now you are reading current passing through the meter. Expect a number <4 Amps.

I would not expect this to be a very high Watt panel, given the dimensions. It may not be worthwhile keeping it at all.

BB.

Re: How To Meter A Panel's Output?

The Voltage with the -_--_-- is the "DC" setting. That is the correct one to use for your DC readings.

The ~ is for AC -- And would not (usually) make any sense on the DC side of your system.

Some reading:

Electricity for Boaters - BoatSafe.com
How to use a DMM (PDF download)

And one warning... With your meter set to volts--it is pretty safe to test any reasonable working voltage system (AC house, DC system, etc.).

HOWEVER, when set to Amps/Current--The leads are now setup to be (roughly) a dead short. If you put the leads across any "live" power circuit, it can easily damage your meter or worse.

Similarly, depending on the meter (but mostly older mechanical meters), when it is set to "Ohms", connecting to a live power circuit can damage your meter.

-Bill

vtmaps

Re: How To Meter A Panel's Output?

BB. wrote: »

HOWEVER, when set to Amps/Current--The leads are now setup to be (roughly) a dead short. If you put the leads across any "live" power circuit, it can easily damage your meter or worse.

But you do want to short out your panel with the meter (that's how you measure Isc). Your panel is limited in how much current it can provide... in that sense it is NOT a "live" power circuit that Bill warned you of.

Cariboocoot wrote:

For Isc you need full illumination of the panel. The meter needs to be set to DC Amps and able to read at least 10 Amps (that is the limit on most DMM's). You connect the leads the same as with Voc, only now you are reading current passing through the meter. Expect a number <4 Amps.

In some meters, to measure current, you must insert the Pos (+) lead into a different jack on the meter (it may not suffice to just set the function switch to DC amps).

--vtMaps

EDIT: I just saw your other post with a picture of the meter. It looks like you do not need to use a different meter jack to measure current.