Troubleshooting assistance, learning

[grandam88]

8x100 watt JJN solar panels NEW
4s2p? configuration@ 80 volt 10amps
AmpInvt 60 amp MPPT
10 gauge from arrays to 8 gauge once paralleled
30 amp disconnect between pv and mppt

On new install, was getting 720 watts from this set up in mostly ideal conditions. Originally set up as 8P set up. Was concerned about voltage drop, converted to 4p2s @ 40 volts. Started getting max 550 watts.

Then convertered to 4s2p @ 80 volts to further drop amperage. Still getting 550 watts max.

Changed to AmpInvt 60amp mppt from Ecoworthy 60amp mppt. Still getting 550 watts.

I'm new to solar but not new to electronics and electrical troubleshooting at an intermediate level. Have the proper tools for the job. Fluke DMM and Fluke clamp DMM (DC/AC amps)

I'm to the point I believe I have a bad Mc4 connection or a bad panel. However, I think it's odd that a bad connection wouldn't improve when cutting amperage on pv circuit in half when doubling voltage. The increased resistance of a bad connection should be less relevant with lower amperage, higher voltage, producing an improvement in overall wattage @MPPT. However, this hasn't been the case. Obviously a bad connection needs to be dealt with, not advocating to ignore this issue, if it exists.

The consistency of the power output (550 watts) leads me to believe the issue is a panel.

I expect lower output with heat, it is currently 92F during the day and I know the panels are much hotter. However, the decrease, imo, is too drastic to point to it as the cause.

This leads me to my questions;

Am I missing something?

Can I short circuit test the 4s arrays to isolate the issue to an array, safely? Or must I test each panel individually?

I'm reluctant to short an array producing 80 volts at 5 amps.

Is it safe to short circuit the entire array and test? This would be 80 volts @ 10 amps.

EDIT- this also occurs with batteries at low charge during bulk mode.

 

[Mattb4]

If all in parallel wwere producing 720w that would be a good indication that the panels are working. It is actually quite good to get 75-80% and you had 90% output. Having that drop to 550w under different types of hookup would have me looking for a bad connection. I would not short your array however you can take clamp on readings at each panel, and strings when operating in daylight, and see if your readings are in line with each other.

 

[grandam88]

If all in parallel wwere producing 720w that would be a good indication that the panels are working. It is actually quite good to get 75-80% and you had 90% output. Having that drop to 550w under different types of hookup would have me looking for a bad connection. I would not short your array however you can take clamp on readings at each panel, and strings when operating in daylight, and see if your readings are in line with each other.

I agree. However, this was a few weeks ago that I was able to get 720watts.

Is it possible that a panel could have become comprimised since then?

 

[grandam88]

I agree. However, this was a few weeks ago that I was able to get 720watts.

Is it possible that a panel could have become comprimisee since then?

Also, I tried to go back to all parallel as a troubleshooting step and still got 550 watts max.

Oddly, I can hit the 550 watts before noon and stay there until around 5pm.

 

[Mattb4]

Also, I tried to go back to all parallel as an troubleshooting step and still got 550 watts max.

Oddly, I can hit the 550 watts before noon and stay there until around 5pm.

That would tend to indicate a SCC charging/load limitation. The normal production of a solar panel is a curve. Low in morning, rising to a peak in midday, and than dropping until sunset.

 

[grandam88]

I'm understand. This has occured across two controllers despite soc. Currently, my mppt outputs this wattage during bulk charge ( correct term?) mode.

I recently ran my lifepo4 bank down to bms low voltage. During the charge time back up, it displayed 550 watts.

I'm going to check my connections and possible run a wire directly to mppt, bypassing camper 8 gauge wire and connections.

 

[grandam88]

After changing out my 10 gauge wire and connectors that connect one array to the next, I am hitting 700 watts with light on/off cloud cover.

I am going to inspect my wire and connections I removed to see if I can find the fault.

 

[grandam88]

I found a loose fitting mc4. The metal contact wasnt able to lock into the connector as designed. This could have caused a bad connection by allowing the crimped contact portion to back out of the connector when pushed together to make a connection.

Producing 650-700 watts now.

I made the mc4 connection. This is a lesson in making proper connections. Loose connections create heat and could lead to a fire.

In this situation, it isn't likely. However possible. In parallel, like it was, the higher amperage would have definitely increased the fire hazard of the bad connection.

I appreciate your assistance

 

[Mattb4]

Glad you found the issue. It can be tricky at times. I had some inline MC4 fuses that simply never were any good at connecting. It took some effort at troubleshooting to figure out the best option was to toss them and go to a combiner box instead.