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 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] >> 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> 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] 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 >> >> >> _______________________________________________ >> 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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