PowerWall 2 Interface with a Generator

[shs1]

Today the local installer came out and we put the generator interface through its paces. It all worked as or better than expected. When the grid was switched off, the house without a delay received power from both the PW2 and solar panels with as suggested the percent charge showing up as suggested. I then went to the house and turned the large burner on the induction cooktop to double boost and then also turned on the electric oven. When the demand exceeded the PW2’s 5kW limit, it shut down and within a few seconds the generator started. The generator transfer switch did its thing and the house was then running on the generator. A few minutes later the solar and PW2 came back on line and the solar charged the PW2 while the generator provided power to the house. When the grid was turned back on, normal operation of the grid, PW and solar resumed.

I also have a manual control in the garage that allows me to turn the generator on and off remotely during a power failure if I anticipate the need for more power than the single PW can provide rather than waiting for it to fail. Some of this is working better than I expected and I am trying to understand exactly why, but for now, this is all pretty good news, especially as there seems to be a real storm in the area right now.

Now if I could only get my second PW and find a way to keep my iPhone charged while continuously monitoring the PW flow. Perhaps in a few days I'll tire of the dance of the dots.

 

[Kbra]

Today the local installer came out and we put the generator interface through its paces. It all worked as or better than expected. When the grid was switched off, the house without a delay received power from both the PW2 and solar panels with as suggested the percent charge showing up as suggested. I then went to the house and turned the large burner on the induction cooktop to double boost and then also turned on the electric oven. When the demand exceeded the PW2’s 5kW limit, it shut down and within a few seconds the generator started. The generator transfer switch did its thing and the house was then running on the generator. A few minutes later the solar and PW2 came back on line and the solar charged the PW2 while the generator provided power to the house. When the grid was turned back on, normal operation of the grid, PW and solar resumed.

I also have a manual control in the garage that allows me to turn the generator on and off remotely during a power failure if I anticipate the need for more power than the single PW can provide rather than waiting for it to fail. Some of this is working better than I expected and I am trying to understand exactly why, but for now, this is all pretty good news, especially as there seems to be a real storm in the area right now.

Now if I could only get my second PW and find a way to keep my iPhone charged while continuously monitoring the PW flow. Perhaps in a few days I'll tire of the dance of the dots.

Can you recharge you PWs from the generator as well during a grid outage and no solar?

 

[shs1]

No I can't charge the PW2 from the generator. The way my system is configured, the generator and the PW2 never see each other – the generator is isolated. While it would be ideal to charge the PW2 from the generator, that would conflict with the need to only charge the PW2 from renewables, which is a requirement here is California, and I think the U.S. in general if you want the various incentives.

 

[miimura]

Can you recharge you PWs from the generator as well during a grid outage and no solar?

You have to put a grid tie inverter between any power source and the Powerwalls in order to inject power into the system. I have shown that this does work with small grid tie inverters and a DC source (Powerwall 2.0 Backup Runtime Extender) and another guy in Australia used a bridge rectifier on an ICE generator with a surplus solar inverter. I don't know if he finally got it working smoothly or not.

 

[technerdx6000]

Another guy in Australia used a bridge rectifier on an ICE generator with a surplus solar inverter. I don't know if he finally got it working smoothly or not.

I did!!

However, there are a few caveats.

1. You need a bridge rectifier and a very large capacitor (I've used a 18000uf @ 400V one).
2. Your output will be only 50% of the inverter's capability (due to DC voltage ripple).

These caveats can be resolved by using a 3 phase generator (I would use diesel) as it eliminates the voltage ripple. Use a bridge rectifier on each phase and tie the positives together on the DC side.

I can output 1.6kW from my setup. My generator is capable of 5kW. If I had a 10kW inverter, I could output the full capacity of the generator. However I only have a 3.3kW inverter.

I have spare inverters lying around, however if I try to connect them into each GPO on the generator (it has 2) with separate rectifiers and capacitors to increase output, the inverters trip (don't know why yet).

I have created a program to automatically log whether we have a grid connection not not and the PW2 charge level. If the grid is down and the battery goes below 20% the generator automatically starts and feeds the house. If the house consumption is less than 1.6kW, the PW2 charges from the generator.

 

[asdruvalr]

Anyone know where I can find more info for a similar configuration to what's been listed?

I'm trying to get a Generac setup with all these fires going on.
Already have 2x Powerwall2s at home. Plenty of solar doing the backup right.
Just want that extra mile.

 

[jakespeed]

read attached pdf, it's for off-grid but still useful info

just had a 22kw generac with 3 powerwalls & solar installed this week

tesla's backup gateway is ats between utility & solar/battery & it feeds the generac ats as the utility feed

there's a pair of current transformers on the generator supply lines

if the generator kicks in the tesla app will show kw's coming from the genreac

 

[diyguy]

read attached pdf, it's for off-grid but still useful info

just had a 22kw generac with 3 powerwalls & solar installed this week

tesla's backup gateway is ats between utility & solar/battery & it feeds the generac ats as the utility feed

there's a pair of current transformers on the generator supply lines

if the generator kicks in the tesla app will show kw's coming from the genreac

WOW! An actual Tesla design for off-grid PV with generator!
Congratulations! I have a PW without PV so I’m going to have to study this to see if it would still apply (and if I’d need a second PW). But I would think that an on grid system that had a transfer switch at the service entrance would become ‘off grid’ and then could use this design. Clearly Tesla has to be completely on board and actively contribute though.
Looking forward to other commenters.

 

[asdruvalr]

read attached pdf, it's for off-grid but still useful info

just had a 22kw generac with 3 powerwalls & solar installed this week

tesla's backup gateway is ats between utility & solar/battery & it feeds the generac ats as the utility feed

there's a pair of current transformers on the generator supply lines

if the generator kicks in the tesla app will show kw's coming from the genreac

Awesome! Thank you. Reading through it, kinda makes me want to stick to their compatible generators, but you said you had a Generac done without issue.

I'm a little confused on the transfer though. Correct me if I'm wrong, but if I add the generator to my setup:

If the power goes out, my loads switch to batteries w/ solar.
Then if I use too many loads, the ATS switches to the generator. Pretty neat.
But what if I ramp down my loads? Does it go back to being powered from the powerwalls?


Thanks guys! With everything going on, I really appreciate the feedback.

 

[jakespeed]

Awesome! Thank you. Reading through it, kinda makes me want to stick to their compatible generators, but you said you had a Generac done without issue.

I'm a little confused on the transfer though. Correct me if I'm wrong, but if I add the generator to my setup:

If the power goes out, my loads switch to batteries w/ solar.
Then if I use too many loads, the ATS switches to the generator. Pretty neat.
But what if I ramp down my loads? Does it go back to being powered from the powerwalls?


Thanks guys! With everything going on, I really appreciate the feedback.

there is no communication between the generator and tesla, so any model generator will work

tesla uses 2 current transformers clamped around the generator feed lines to display generator kw on the tesla app

ats switching is not load based

if tesla's ats senses utility is out, then it uses solar/battery

if the generator's ats senses the utility/solar/battery are out then it starts the generator & switches over

i suppose if utility was out & you overloaded your solar/battery you would trip a breaker & the generator's ats would believe solar & battery were out & start generator

 

[asdruvalr]

Awesome. I think I get what you mean, Jake.

Sounds like I'll have power for awhile going with this combo. Appreciate the help everyone.

 

[dsereni]

Today the local installer came out and we put the generator interface through its paces. It all worked as or better than expected. When the grid was switched off, the house without a delay received power from both the PW2 and solar panels with as suggested the percent charge showing up as suggested. I then went to the house and turned the large burner on the induction cooktop to double boost and then also turned on the electric oven. When the demand exceeded the PW2’s 5kW limit, it shut down and within a few seconds the generator started. The generator transfer switch did its thing and the house was then running on the generator. A few minutes later the solar and PW2 came back on line and the solar charged the PW2 while the generator provided power to the house. When the grid was turned back on, normal operation of the grid, PW and solar resumed.

I also have a manual control in the garage that allows me to turn the generator on and off remotely during a power failure if I anticipate the need for more power than the single PW can provide rather than waiting for it to fail. Some of this is working better than I expected and I am trying to understand exactly why, but for now, this is all pretty good news, especially as there seems to be a real storm in the area right now.

Now if I could only get my second PW and find a way to keep my iPhone charged while continuously monitoring the PW flow. Perhaps in a few days I'll tire of the dance of the dots.

Hello, It is so great that you were able to get your Tesla PWs to work this way! We are designing a Generator system for a customer who has two PW's and wondered if you would be willing to share the logic of how you system works. We are working with an engineering firm tp detail the installation and once we get it drawn up we would be willing to share it so other could take advantage. [email protected]

 

[h2ofun]

Hello, It is so great that you were able to get your Tesla PWs to work this way! We are designing a Generator system for a customer who has two PW's and wondered if you would be willing to share the logic of how you system works. We are working with an engineering firm tp detail the installation and once we get it drawn up we would be willing to share it so other could take advantage. [email protected]

I would also like to get how this was done. [email protected]

 

[Vines]

I would also like to get how this was done. [email protected]

Generator integration is already built into the Powerwalls, it just can't charge batteries.

Simply put the ATS and generator downstream of the gateway, between the TEG and the essential loads panel. The generator becomes the backup to the backup.

 

[jhn_]

Generator integration is already built into the Powerwalls, it just can't charge batteries.

Simply put the ATS and generator downstream of the gateway, between the TEG and the essential loads panel. The generator becomes the backup to the backup.

Exactly. This is the way we are wired up with whole house backup. If the Grid goes down the Powerwalls kick in, if the Powerwalls are depleted the generator kicks in.

 

[h2ofun]

Exactly. This is the way we are wired up with whole house backup. If the Grid goes down the Powerwalls kick in, if the Powerwalls are depleted the generator kicks in.

That is standard wiring, which I already have wired this way. Title of this thread is funny. Assumption is one could charge ones powerwalls if no solar and power out. Oh well.

 

[Vines]

That is standard wiring, which I already have wired this way. Title of this thread is funny. Assumption is one could charge ones powerwalls if no solar and power out. Oh well.

If you have an off-grid system it will recharge batteries, instead of how I described above.

There are a few posts about how to recharge the PW from generator power by fooling the GW2, but this is not Tesla supported except one of the 2 ways I described above.

 

[shs1]

Attached is the diagram of my installation of Powerwall(s) with a generator. As was discussed above it took many months for Tesla to approve of any installation where a generator was involved, but this setup which we proposed assured that the Powerwalls Tesla Backup Gateway would never “see” the generator and finally Tesla allowed the installation to go forward. Obviously the generator cannot be used to charge the Powerwall(s) in this configuration.

Although, at the time, Tesla insisted that the generator related transfer switch be only manual, our installation used an unmodified Kohler ATS associated with our 18 kW Kohler generator. As discussed above, if during a power failure, the Powerwall(s) go into standby for any reason, the ATS detects this, starts the generator, and connects the generator to the house, isolating the Powerwall(s) and solar. In this condition the solar can and does charge the Powerwall(s). I was concerned that there may be an unstable condition where the generator ATS would see the voltage from the recovering Powerwall(s)and switch back to it, only to fail again if the load was too great. In practice I have not seen this happen, but I realize it could.

For that and other reasons, I do have manual control of the ATS from a switch inside the house (the generator and Powerwall(s) are ~200 yards from the house) so that if I anticipate a load that the Powerwall(s) can’t handle or the SOC is getting low, I can force the generator ATS to connect the generator to the house and leave the solar and Powerwall(s) isolated. In this manual mode of operation, it will also not detect the grid coming back online, so under those circumstances I must monitor the grid separately and act accordingly.

Although Tesla strongly opposed any installation with a generator involved when we started this project, they do today, but with a configuration like the one we worked out with them that assures the Powerwall(s) and generator are isolated from each other. I even see a generator icon in the Tesla app, but have yet to install the CTs necessary to use that feature.

 

[kms123]

I joined just to reply to this thread, which I found very helpful. We have a single Powerwall 2 and a minimal solar setup, really just to protect us against semi-regular but typically brief power outages in our area. I've wanted to incorporate greater protection against longer outages, but did not want to invest in a much larger solar system.

I managed to find this document on tesla's site which displays a number of powerwall configurations that incorporate a generator. Here's the link,

https://www.tesla.com/sites/default/files/Tesla Product Suite Prewire Guidance.pdf

and the document, just in case it disappears from the web.

 

[kms123]

Here's two images from the document I posted. I believe the first is equivalent to your installation: