Some of my Arrays are Outputting Volts but no Amps. Why?

x0054

We recently purchased a house with a 20 panel array installed on it. The house was built in 2001 and the panels were installed around 2002 or 2003. The house is off the grid, so all of the power is generated by the array.

Recently while doing some routine maintenance on the system we ran a diagnostic test on the array and found out that about half the panels are not working. The panels are arranged in a 2S10P configuration with the system voltage of 75V, each panel is a 35V 140W unit from BP. Out of 10 arrays 5 output normal amperage in the 1.8-2.2A while the other 5 are barely outputting 0.08-0.18A. We isolated each of the 10 arrays and tested the voltage independently, and they all were in the 76-78V range, so all appear to be working with no shorts, but still, about half are not outputting current.

We checked all of the wiring, and it all looks good. Any suggestions. Also, has anyone had to deal with the BP Solar warranty department. Any tips?

 - Bogdan

westbranch

Bill, the moderator, 'BB' IIRC had a warranty replacement of some panels, so he is probably the best to comment on what happened...
Did you retorque ALL the connections?  that can be a hidden issue...
Interesting that 1/2 of the strings are in the same Amperage range... ~ 0.1A to 0.2 A... What were the test conditions, Midday? Shade? cloudy? Hot/Cold?

x0054

Thanks for the response. Yeah, I checked all of the wiring 3 times now, nothing is wrong with the wiring as far as I can tell. Just to be on the safe side I am going to individually check the panels later on. Since they are arranged in pairs, I am hoping that maybe one panel per pair failed, so I can salvage at least some of them. I am very surprised that they failed like that rather than more progressively.

Test conditions were around 48F with 90 degree sun looking that the panels (it was 2PM or so, but they are on an angle). I recently upgraded the solar charger the house came with. The original system had a PWM charger, and I switched it to MPPT charger with logging functions, the Morningstar TriStar MPPT-60. The array is 2.8kW nominal, but day to day the max I am getting is 1.2kW. One of the days I got 2.2kW but only for an hour or so. It's a little strange, maybe the charger is somehow not playing nice with the panels? But they are all paralleled up, so there is no reason it should work with some of them but not the others. I am no expert, but based on what I understand about how MPPT charges works, it really shouldn't be an issue.

BB.

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Some of my Arrays are Outputting Volts but no Amps. Why?

I will lock this one.

-Bill