Solar panel testing for the lazy

[Bluedog225]

I had a relapse yesterday and picked up another 20 solar panels at restore. 275 watt LG panels at about $30 each. Now I’ve to about 75 used panels. I hope to deploy about 50 before it warms up in May.

I’d appreciate any tips for testing solar panels. I plan to test open circuit voltage, short circuit current, and current at max power. Those that pass will be put in the deploy pile and if they fail, I’ll put them in the diagnose and fix pile. My plan is to set up a stand where I can put the panel up, hook it up via mc4 connectors and have a battle born and little charge controller.

Two questions, I am planning to use my clamp multimeter. Or is there a little gizmo that will test all at once? I’d like to make this as easy and quick as possible.

Second, is there anything else I need to test?

Thanks

 

[timselectric]

This is what I use.

https://a.co/d/5krnek0

 

[Samsonite801]

I bought one of these and it seems to work pretty good:

Amazon.com

It can get a little hot after continual use and may shut itself down until I let it cool down for a bit (on a hot day). It does have a little cover plate on the back you can remove (kind of looks like a battery cover, where the 3 FETs are right under it). I just leave that off and it exposes the FETs inside to better airflow, and it will stay cooler for longer before shutting down.

But it does work decently well overall.

It looks the same as the one timselectric posted (except for the wattage rating), his looks a bit cheaper price than the one I purchased though... I guess it will just come down to price, or whether you like the way one brand name or another sounds when it rolls off your tongue.

 

[Bluedog225]

Great. Thanks!

 

[Samsonite801]

Great. Thanks!

Yeah, it's not to say it's a bad designed meter just because it gets hot. I don't think it's a bad design, as it is a lot to ask for a device that has to burn off power (somewhere) in order for it to take your measurements. I think it is a great unit. I am just wondering about putting a little fan (maybe powered off of the unit itself, soldiered onto the board somewhere) over that area where the cover plate is, so it has an active cooling, then it may be able to stay on longer for extended panel testing.

Like if you just plug it in for a minute for a quick test, it doesn't ever shut down (being mindful of duty-cycle). It was when I left it plugged in longer periods where we were testing various different angles, and face-down (checking bi-facial gain), and after some time the heat just builds up and trips its own temp protection because it has nowhere to dump that energy but heat.

 

[Bluedog225]

Good to know. I’m interested in a quick check then unplug. So heat shouldn’t be an issue.

 

[timselectric]

Just make sure that you pick one that is rated for the highest wattage panel that you think you will ever test.

 

[Orangesauce]

I was also wondering this, bought one of these pallets that arrived last week and I probably ought to test the panels.

Want to find something fun for my 13yo to do with them as well before they go on the roof. Not all of them, of course!

 

[Bluedog225]

The tester Tim recommended is great. Easy to use. Good info displayed. Seems solid.

 

[Steve777]

Just out of curiosity, what does this sort of meter offer over say a DVM with 20-30A current capabilities? Seems that if one check the Voc and Isc on a panel in bright sun, you would have a pretty good idea if it is functioning up to specs.

 

[Samsonite801]

Just out of curiosity, what does this sort of meter offer over say a DVM with 20-30A current capabilities? Seems that if one check the Voc and Isc on a panel in bright sun, you would have a pretty good idea if it is functioning up to specs.

This type of tester actually loads the panel down to maximum power watts (Pmax).. Voc and Imp are at opposite ends of the circuit resistance spectrum and don't really say much about watts you'll see at MP.

Sure, it's better than nothing, to check Voc, then short the panel and check Isc with an amp clamp, but hey, if I have a meter that can test MPP watts then I can do all kinds of other tests too, like time of day / season, panel angles, shading tests, etc..

 

[Orangesauce]

The tester Tim recommended is great. Easy to use. Good info displayed. Seems solid.

That's the one I bought! I like all the info on the screen.

Sure, it's better than nothing, to check Voc, then short the panel and check amps with an amp clamp, but hey, if I have a meter that can test MPP watts then I can do all kinds of other tests too, like time of day / season, panel angles, shading tests, etc..

After spending $2500 on used panels, it seems like spending another 4% to test them makes sense before putting them on the roof or waiting too long and upsetting the seller with any potential claim.