Jay, The Tesla Gateway has a 12v input terminal for boot up. To startup my off grid Powerwall we wired in a 12V power supply to the input terminals and plugged the other side into a grid-connected outlet. Some version of this is part of their off grid process.
We’ve been running a reasonable portion of our offices off grid with a Powerwall since the winter. Other than a microwave incompatibility issue, it seems pretty reliable and has a more friendly user-interface than most manufacturers. I cannot speak to generator backup with the Powerwall as I have not personally been in this situation (in an emergency we could manually transfer back to grid). I do know they now have a few approved generators for off grid. I just haven’t done that. Matt From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> On Behalf Of Jay Sent: Tuesday, July 21, 2020 11:53 AM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] Tesla Powerwall 2.0 - Experience?/Generator charging Connecting a generator output to the inverter output has the potential to damage the generator control board. Another way to go is to put a diode on the output of the generator and parallel it into the DC input to the GT inverter. Preferably you’d want a larger generator than the GT inverter. However if it’s smaller the GT inverter should reduce its output if the generator output sags too much. But they might not play that well together. Given all that I’ve heard here, lots of reasons the PW isn’t ready for offgrid. With the specific situation of how do you black start the PW if it’s only ac coupled? this problem is common with all ac coupled systems, but usually you can get a generator/battery charger or dc couple some PV to jump start the system. With the PW, that doesn’t sound possible without surgery, and probably warranty issues. Jay Peltz power. On Jul 21, 2020, at 7:52 AM, drake.chamber...@redwoodalliance.org<mailto:drake.chamber...@redwoodalliance.org> wrote: Larry, Connect the coil of a 240 VAC contactor to the output of the generator circuit. Have the contacts of the relay break the AC coupled feed. Drake --- On 2020-07-20 16:25, William Miller wrote: Larry: If you can automate disabling grid-sell when connected to the generator in a fool proof manner then you may have a solution. If the system fails I see a damaged generator but not a life-safety issue. William From: la...@starlightsolar.com<mailto:la...@starlightsolar.com> [mailto:la...@starlightsolar.com<mailto:la...@starlightsolar.com>] Sent: Monday, July 20, 2020 1:19 PM To: William Miller; RE-wrenches Subject: Re: [RE-wrenches] Tesla Powerwall 2.0 - Experience?/Generator charging Hi William, Thank you for your response. I was responding to the question of use off grid and Hiltons question about generator use. Jason said, "But Tesla is clear in that they do not allow a generator to interact with the Powerwall in any way." This is true. Powerwall uses AC coupled inverters for off grid charging. If AC from the micro-inverters was switched off and the generator provided the 240 Volt to the Powerwal inverter inputl, would that not be a temporary solution to the generator prohibition? The power wall would see incoming power and sync. Of course, the system must be monitored. If the power wall calls for cutback or disconnect by raising frequency, the generator should be disconnected, if it indeed works like that. If Powerwall provides an internal disconnect, then it would be safer for the user. Just trying to think outside the box. Larry Crutcher Starlight Solar Power Systems <image002.png> On Jul 20, 2020, at 12:01 PM, William Miller <will...@millersolar.com<mailto:will...@millersolar.com>> wrote: 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<mailto:re-wrenches-boun...@lists.re-wrenches.org>] On Behalf Of la...@starlightsolar.com<mailto: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<mailto: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<mailto: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<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org> _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org> _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org>
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