Larry:
I am not Tesla conversant but allow me to speculate: If any grid-tied system can be fed from a generator it could also feed back to the generator, which may damage said generator. The grid-tied system should therefore be connected upstream of any transfer switching, making it ineligible to be charged from the generator. William *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *la...@starlightsolar.com *Sent:* Monday, July 20, 2020 10:52 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] Tesla Powerwall 2.0 - Experience? Since the Powerwall is AC coupled, how will it know if the power source is a PV solar array or a generator if either feed the PV input? It seems simple AC switching is all that would be needed. I like to think outside the box but I’m not familiar with Powerwall. Larry Crutcher Starlight Solar Power Systems On Jul 20, 2020, at 9:53 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
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