New Powerwall off-grid test problem, thanks for suggestions.

[Regnad]

The solar setup is 6 years old using Enphase M215 micro-inverters with no issues. 2 Powerwalls were just installed in the garage 65 feet from main panel. Everything working ok so far.

Off-grid test:

After disconnecting the main panel from the grid, the solar power output became erratic, was about half of normal and disappeared entirely several times. This was shown in both the Tesla and Enphase apps. When the air conditioner turned on, all house power shut off so I re-connected the grid which had been disconnected for about 3 hours for this test.

Thanks very much for any suggestions!



My guess...

Perhaps the distance (65 feet) between the batteries and the M215 inverters is too far for the Powerwalls to (1) correctly load them and (2) supply instant power to the AC compressor? A single AC (green/red/white/black) line connects the 2 batteries to the main panel. Perhaps lower gauge or individual battery lines? I really don’t want the batteries outside by the main panel.

Thanks again!

Nick

 

[power.saver]

Was the battery over 98% when the solar shut off? If so, this is normal.

Your AC has too large a startup draw (LRA is too high) and turning it on will shutdown the PW. What is the LRA of your AC unit (should be shown on the condenser label).

 

[Regnad]

Thanks. The batteries were at 85%, set to self-powered. Solar shut-offs were only occasional, lower and very erratic output was constant. The compressor LRA is 112. Thanks again!

 

[Regnad]

Is that 27kW?!! No way.

 

[power.saver]

Yes it is, and a LRA over 7kW x number of PW will be a problem. Did they install a soft start (SureStart) on your condenser? If not, it's not going to work, as you saw.

My AC has a LRA of 127, and even with soft start, it's still too much for my 2 PWs, so I have it outside the backup circuit.

 

[miimura]

How large is the solar system and how many kW were the PWs charging at when they were unstable? It is possible to overload the PWs with too much solar, so they will change the frequency to push the solar offline to avoid reaching the charging power limit. That said, you should need more than 10kW of solar to overload a pair of Powerwalls.

My two Powerwalls work well with my 18 M215 Enphase micro inverters. However, this is the start of the solar doldrums for me. My max solar output was 1.9kW and 4.0-7.1kWh per day in the past week.

 

[Regnad]

Peak output these days is about 6kW. Am I doing the math right?: 41 panels times 215 watts is 8.8k which seems right as a maximum. The system works great until I physically unhook the grid.

Thanks so much for the suggestions!

 

[Dan123]

The solar setup is 6 years old using Enphase M215 micro-inverters with no issues. 2 Powerwalls were just installed in the garage 65 feet from main panel. Everything working ok so far.

Off-grid test:

After disconnecting the main panel from the grid, the solar power output became erratic, was about half of normal and disappeared entirely several times. This was shown in both the Tesla and Enphase apps. When the air conditioner turned on, all house power shut off so I re-connected the grid which had been disconnected for about 3 hours for this test.

Thanks very much for any suggestions!



My guess...

Perhaps the distance (65 feet) between the batteries and the M215 inverters is too far for the Powerwalls to (1) correctly load them and (2) supply instant power to the AC compressor? A single AC (green/red/white/black) line connects the 2 batteries to the main panel. Perhaps lower gauge or individual battery lines? I really don’t want the batteries outside by the main panel.

Thanks again!

Nick

How large is your solar array? How many panels and how many M215 inverters? It is possible that you have too many for 2 powerwalls.

When you first disconnect from the grid, it is normal for the solar inverters to shut down. They should restart in 5-10 minutes. After

 

[Dan123]

Peak output these days is about 6kW. Am I doing the math right?: 41 panels times 215 watts is 8.8k which seems right as a maximum. The system works great until I physically unhook the grid.

Thanks so much for the suggestions!

Yes, 8.8 is the maximum. It should be within the capacity of the 2 powerwalls to charge. Unless the temperatures were very cold.

If your system is not working very well at 85% powerwall state of charge, then there is something wrong with the configuration.

 

[Merrill]

Wondering how you determine what the LRA needs to be for the powerwalls to work. The companies that came out to quote for 2 powerwalls with my 6.5kW solar said it would run my well pump which has a LRA of 53.

 

[Dan123]

Wondering how you determine what the LRA needs to be for the powerwalls to work. The companies that came out to quote for 2 powerwalls with my 6.5kW solar said it would run my well pump which has a LRA of 53.

It's basically about 29 amps per PW (7000/240). So LRA 58 is the max for 2 PWs.

 

[Merrill]

It's basically about 29 amps per PW (7000/240). So LRA 58 is the max for 2 PWs.

Ok, thanks

 

[runfarnn]

Here is what the Tesla engineer designing our system provided as specs for a 2 PW set up (with two A/C units).

The LRA for each unit is 58 amps or less

OR

The LRA is 140A or less AND the unit has a scroll compressor.

 

[charlesj]

How large is the solar system and how many kW were the PWs charging at when they were unstable? It is possible to overload the PWs with too much solar, so they will change the frequency to push the solar offline to avoid reaching the charging power limit. That said, you should need more than 10kW of solar to overload a pair of Powerwalls.

My two Powerwalls work well with my 18 M215 Enphase micro inverters. However, this is the start of the solar doldrums for me. My max solar output was 1.9kW and 4.0-7.1kWh per day in the past week.

I have 17 of those micros as well.
Did you try the test Regnad performed? Should I be worried as well?
I don't have AC so perhaps I may be ok.

 

[miimura]

I have 17 of those micros as well.
Did you try the test Regnad performed? Should I be worried as well?
I don't have AC so perhaps I may be ok.

My system works as expected. My backup history shows 22 events and 12 total backup hours over about 20 months, after excluding my own tests when I flipped the main breaker. I have not made any special request to Tesla to address the 66Hz issue, but I have only seen it happen when the batteries are very full.
I also don't have A/C, but I don't think that's a factor for solar stability.