This, from a Nov 03, 2017 Powerwall 2 document, makes sense. Generator input in place of utility syncs with PV inverters and Powerwall inverter.
Thank you, Larry Crutcher Starlight Solar Power Systems On Jul 20, 2020, at 1:25 PM, August Goers <aug...@luminalt.com> wrote: Tesla released new offgrid design and installation instructions April of this year. As a Powerwall dealer, we're under NDA not to share the document, but the Powerwall will now charge from the generator when it hits a certain SOC threshold if the PV is not running. I'm not sure about that caveat of not allowing the generator to run while the PV is running. It seems like there are plenty of times where there is low solar production and you want to fire up the generator to top off the batteries. They also have a low state of charge mode when SOC reaches 10%, that the Powerwall will turn on during the day for short periods of time just to test to see if the PV system will couple up to charge the battery. This AC-coupling method of reviving the battery may or not work depending on loads and PV sizing / production levels. One limitation to the NMC battery technology is that it doesn't work well particularly in the cold, so offrige Powerwall batteries should be installed in the heated envelope of the home. August On Mon, Jul 20, 2020 at 10:09 AM Jason Szumlanski <ja...@floridasolardesigngroup.com> wrote: The Powerwall 2 is now supported by Tesla in an off-grid configuration from what I heard. It is AC coupled. It cannot interact with generators whatsoever. You can't charge the battery with a generator and you can't AC couple a generator to it. If you want a generator, you put a transfer switch on the load side of the gateway device. If the battery dies, the generator starts. The generator powers loads, but does not recharge the battery because it becomes isolated via the transfer switch. The big downside I see with that is there would be a loss of power to the loads until the generator fires up. I don't see a way around that. I'm not a Tesla certified installer, but I have seen some of these batteries out in the wild and that's just the way it is - it's an integrated unit. I'd call it an "AC Battery," kind of like an AC PV Module. To answer another point in this thread, if the battery reaches its LBCO it can only recharge with PV in an off-grid scenario. It reserves battery capacity to turn on occasionally to see if there is PV input. At least that's how I understand it to work. I don't know what would happen if the battery actually reached 0%. Seems risky. I'm not sure how you would "jump start" it. Publicly available details seem scant on this, but there are a few system owners talking about it if you dig deep on the Interwebs. It will be interesting to see what Enphase comes up with. There are generator inputs on their Ensemble system, but no software support for this yet. The concept is very similar to Tesla in that there is a gateway device, essentially a transfer switch with battery controls inside. The Gateway acts as the AC point of coupling for everything to tie in together. I'm not sure why you couldn't use a generator to charge the Powerwall battery the same way you would charge with the grid. However, you would need a way to disable PV AC coupling when the generator is running. I can see how Enphase would be able to do this pretty easily. But Tesla is clear in that they do not allow a generator to interact with the Powerwall in any way. Jason Szumlanski On Sun, Jul 19, 2020 at 11:43 AM Hilton Dier III <hiltond...@gmail.com> wrote: Greetings, Wrenches, I have an off-grid client who has been reading the buzz about the Tesla Powerwall 2.0. I have been reading the data sheets and manual for it and it appears to be AC coupled only. There was talk of a DC input version, but apparently that fell by the wayside. I try to be agnostic about technology, and I'd be willing to subcontract a Tesla-approved installer if, in fact, this was the best solution. Does anybody have experience using the Powerwall 2.0 in an off grid PV system? Is it AC coupled only? Can it take generator power without barfing? What is the lead time on these? Many Thanks, Hilton -- Hilton Dier III Missisquoi River Hydro Renewable Energy Design _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
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