I'm having a 3 PW2 system installed but my summer solar generation ( about 16KW) capacity greatly exceeds the 3 x 14.5 KW = 43.5 KWHr storage capacity of the 3 PW2s. Before jumping into the 3 PW2 cost, I reviewed the possibility of doing a DIY system
Building my own pseudo(Powerwall) based on L-P-Gs
Building my own pseudo(Powerwall) posts. He did a nice job that seems quite feasible but I decided against it because of the difficulty of it being illegal and not possible to get a permit. I suspect the PW2 done legally will add value to my home thats in the PG&E fire power shutoff area and an illegal install would be a headache. So I'm asking another question on the forum.
It seems much of the battery and inverter work L-P-G did could be reused with a different coordination controller.
Has anyone considered or seen anyone who has successfully installed expansion capacity for their PW2 installation to increase the capacity to match their solar production? What I'm thinking is that I can install a battery system that is built from 4 or so 5.3KWHr ( 21 WHr) Tesla used batteries that could be in my garage and simply add additional backup that the Tesla system could use ( without knowing it).
It seems like a simpler problem that the full PW2 and all the PG&E, Permit, Automatic disconnect and inverter issues. By charging these batteries while solar power is being generated, the PW2 system would "think" its simply a load in the house it needs to produce. It could also fully charge itself while not in backup from PG&E again looking like a home load.
Then when in backup mode with no PG&E AC, it would need to fool the PW2's into believing it was "less home load" but still be responsive should the PW2's ask it to back off via UL1741 frequency control. The PW2's would then not use their own power charge and the expansion would power the home till it was exhausted and then the PW2's would take over. I haven't looked deeply into the coordination issues with the PW2s but its seems doable and could compensate for people who mistakenly installed only one or 2 PW2's and have discovered they lose Solar power during backup...
It would seem the best strategy would be to find a way to try and generate the actual home power use less some margin and do that until exhausted. Then during the next day, a power monitor on the solar would send a wireless signal to the expansion battery system with the power being generated and that would restart charging. If the solar power dropped due to clouds or whatever, it would stop charging.
It also might make sense to try and put large loads such as air conditioners or EV battery chargers behind an AC disconnect during backup mode to reduce the inverter demands.
Thoughts.
Here is L-P-G's basic design for a full PW2 look alike:
Building my own pseudo(Powerwall) based on L-P-Gs
Building my own pseudo(Powerwall) posts. He did a nice job that seems quite feasible but I decided against it because of the difficulty of it being illegal and not possible to get a permit. I suspect the PW2 done legally will add value to my home thats in the PG&E fire power shutoff area and an illegal install would be a headache. So I'm asking another question on the forum.
It seems much of the battery and inverter work L-P-G did could be reused with a different coordination controller.
Has anyone considered or seen anyone who has successfully installed expansion capacity for their PW2 installation to increase the capacity to match their solar production? What I'm thinking is that I can install a battery system that is built from 4 or so 5.3KWHr ( 21 WHr) Tesla used batteries that could be in my garage and simply add additional backup that the Tesla system could use ( without knowing it).
It seems like a simpler problem that the full PW2 and all the PG&E, Permit, Automatic disconnect and inverter issues. By charging these batteries while solar power is being generated, the PW2 system would "think" its simply a load in the house it needs to produce. It could also fully charge itself while not in backup from PG&E again looking like a home load.
Then when in backup mode with no PG&E AC, it would need to fool the PW2's into believing it was "less home load" but still be responsive should the PW2's ask it to back off via UL1741 frequency control. The PW2's would then not use their own power charge and the expansion would power the home till it was exhausted and then the PW2's would take over. I haven't looked deeply into the coordination issues with the PW2s but its seems doable and could compensate for people who mistakenly installed only one or 2 PW2's and have discovered they lose Solar power during backup...
It would seem the best strategy would be to find a way to try and generate the actual home power use less some margin and do that until exhausted. Then during the next day, a power monitor on the solar would send a wireless signal to the expansion battery system with the power being generated and that would restart charging. If the solar power dropped due to clouds or whatever, it would stop charging.
It also might make sense to try and put large loads such as air conditioners or EV battery chargers behind an AC disconnect during backup mode to reduce the inverter demands.
Thoughts.
Here is L-P-G's basic design for a full PW2 look alike: