Troubleshooting Solar Power Issue - SC Volts, 0 Amps

[wade0000]

Hello,
I am really frustrated with not being able to use logic and tests to determine the cause of an INTERMITTENT problem with my off-grid solar power system in my garage.

Quick system set up:
Four(4) 350W panels (1.4KW) - connected in series-parallel (78V X 18A) max power
EPEVER 40A Charge Controller (Max charging capability is 1.04KW)
Four(4) 12V 200AH AGM batteries connected in series-parallel
3000W Pure Sine Wave Inverter (24V)
Going to two(2) 15A circuits running garage lights, receptacles, outdoor pond pump, outdoor lights, etc.

Here is the problem: Whenever the solar power reaches 800W and stays that way for a couple of minutes... the charge controller shows high voltage (approx SC voltage) and 0 amps and stops charging because of 0 W.
I've tried the obvious things like 1) checking my M4 connections and replacing those that I didn't crimp as well, 2) plugging and unplugging one set of paralleled panels to isolate which group is the problem.
Occasionally the charge controller will start charging again back to normal after about a 5 minute wait.

It seemed to me like I have a bad connection and that the wire/connector is heating up... and then once it cools, the connection begins again. But sometimes it never starts charging again.

Any ideas where to go to look next?

 

[gnubie]

Check those breakers and switches for correct operation. It wouldn't be the first time they have caused problems like this. If you place a multimeter in volts mode across the terminals on them it should read only a few millivolts with several amps flowing.

Check the temperature of the charger. Epever chargers thermally throttle. If the heat is excessive they can turn off. If you can hold your hand on th heatsink indefinitely, heat isn't an issue.

 

[wade0000]

Check those breakers and switches for correct operation. It wouldn't be the first time they have caused problems like this. If you place a multimeter in volts mode across the terminals on them it should read only a few millivolts with several amps flowing.

Very interesting.... I only have one true breaker on the DC side - but it is not tripping. Are you saying that the high amps I am getting right before a cut off could be related to the breaker even if it doesn't trip?

Several manual DC disconnects - very heavy gauge! check those too?

 

[gnubie]

It doesn't have to trip, it might just have poor connections internally that move enough to upset things as it heats up. The style of breaker you are using is well known to be junk grade. There are legit real items in that style, but 99.99% of the stuff on ebay, amazon etc are fake junk.

Check everything, the fault is in there waiting to be discovered.

 

[wade0000]

It doesn't have to trip, it might just have poor connections internally that move enough to upset things as it heats up. The style of breaker you are using is well known to be junk grade. There are legit real items in that style, but 99.99% of the stuff on ebay, amazon etc are fake junk.

Check everything, the fault is in there waiting to be discovered.

That makes sense. It's "supposed to be" 30A 600V breaker.. thank you! I'll check tomorrow assuming the sunshine is good!

Can you recommend a good DIM mountable 30A DC breaker?

 

[gnubie]

I meant the little black things with red buttons and levers, those are the suspect items.

 

[wade0000]

I meant the little black things with red buttons and levers, those are the suspect items.

But those are only after the charge controller between the CC and the inverter and batteries. Sorry, to pester you.. .but wouldn't that take that out of the equation?

 

[gnubie]

If the breaker opens or is defective preventing power flow, even though your panels are in full light you will see 0 (or low) amps and watts reported by the charger. There has to be a path for current to flow out of the charger for the charger to show amps / watts.

Think of the breaker as being a tap. If you close the tap (open the breaker) the counter on the water meter doesn't move even though there might be a 100 gigalitre dam behind the tap.

 

[wade0000]

Great explanation. I'll check the voltage as you mentioned then wire it out of the circuit while at full charge.

Great information! I really appreciate it!@'

 

[wade0000]

UPDATE:

I changed out the cheap 60A DC breaker with another cheap 100A DC breaker and even though it was partly cloudy at the max sun angle, I got up to and stayed at 800W without it going to S.C.

So, I think that was the problem and that is how to fix it.

Goes to show you that you can beat your head against the wall trying to troubleshoot, but there is no replacement for experience which gnubie gave me! Thanks!

 

[Supermo26]

Cool to see some resolution.

 

[schmism]

There are legit real items in that style, but 99.99% of the stuff on ebay, amazon etc are fake junk.

can confirm. The 150a one I bought lasted for 2 pushes of the red button. Then it wouldn't trip. It got replaced with a fuse and a disconnect.

 

[wade0000]

Thanks everyone.

I should have known this issue... because the previous cheap one tripped early at about 30A when it was rated for 60A. I replaced it with another identical cheap one which is the one that was apparently failing but not tripping. So now I raised the level with a 100A one I happened to have. This will be for the time being while I search for and find a decent one or a fuse like schmism did.

 

[wade0000]

FINAL UPDATE: Sunny morning today....so I just tested the new fuse set up and it charged at over 900 W for over 30 minutes without shutting off.

Again, I had previously troubleshot this problem for 2 to 3 full freaking weeks with NO SUCCESS! Then, I join this forum and make a post... and BAM! within a couple of hours the most likely cause and solution are posted. And the solution works!

I would have struggled at this problem for months.... if it had not been for you fine people.

 

[ClinicalScientist]

Just wanted to post a thank you to previous replies. I have the exact same issue with the exact same cheap Amazon breakers. I’m excited to try and troubleshoot tomorrow knowing I might have a culprit.