generator injector for use with AC coupled battery system like powerwall or enphase

[RottenMutt]

i'm looking for a way to connect a generator to either a powerwall or ensemble system and have it charge the batteries.

enphase has this on their road map, but will not state when.

[Ampster]

The only thing I can offer is second hand information. This question is asked ocassionally on the Powerwall threads of the Tesla Motors Club forum and no one has found a way to do that. There are several obstacles. The battery in the Powerwall is not accessible without voiding the warranty. The Powerwalls are often programmed by Tesla specifically NOT to charge from the grid even though they get their energy through an AC coupling mechanism. They rely on CTs interacting with the Tesla Energy Gateway to limit grid charging. There is no generator port on the Powerwall. They may be sensitive to dirty AC from some generators.
You already have an answer from Enphase and I can only speculate that there may be similarities.

[RottenMutt]

a "generator injector" would act the same as a solar inverter, so would be connected to your generation panel so the current would flow thru the tesla CT and would charge the powerwall, really simple. should be designed so the operator can dial in a specific load on the generator, preferably both 120v and 240v compatible.
enphase said this is on there road map. I'm really posting it here so hopefully someone will beat them to it... run with the idea...

[Blacroix]

I work in the networking/telecom world - and have used 48V rectifiers quite often.

In looking at the specs of the SMA Sunnyboy SB3.0-1SP-US-41 - DC input voltage needs to be 155-480v. and DC output is up to 4800w; max AC output is 3000w. I realize that these grid tie inverters are designed to be connected to solar panels - but couldn't someone take four 48v DC rectifiers in series to feed the Sunnyboy inverter instead of solar panels? If the rectifiers were powered by a portable generator - wouldn't that be a way to "fool" a solar battery, like a Tesla Powerwall, to use a generator to charge the batteries?

I read that tesla powerwalls integrate with 3rd party inverters, like sunnyboy and enphase microinverters. I see the Enphase IQ7X is designed specifically for 96-cell (48V) panels.

Would it work if you:
- Fired up a a generator
- Used Gen AC power to connect a 480w, 48v DC "power supply" like https://www.amazon.com/DROK-110V-220...dp/B08GFQZFC1/
- Used that 48V DC to power an Enphase IQ7X

Would this essentially be a way to use a portable generator to essentially backfeed clean, inverter power into the grid (and therefore, into your Powerwall)? If this worked, it seems one would just need to run a handful of these in parallel to get the wattage they desire for charging.

If this did indeed work, then the next challenge would be how to build a controller to turn the generator on and off automatically - but I've read there is an "unofficial" API for the Tesla Powerwall that can get battery % - if that's correct, building a simple python script to poll the API every 5 minutes and build a little logic to fire the generator up at a certain percentage, then turn it off at another set point, would be pretty easy.

Would love to hear some feedback.

Brian

[bcroe]

Grid tie inverters are not designed to provide the power a load might need. They
are designed to find the Maximum Power operating Point of a solar array, and
suck that maximum power out, to be delivered to an infinite power sink that can
easily absorb whatever energy is available. That is not the operational mode
proposed above, so be prepared for maximum smoke.
Bruce (designed 48V stuff for 4 decades) Roe

[Blacroix]

No need to let the smoke out. LOL!

I only use 48v rectifiers to power gear, not to do this stuff. I am just curious, if you kick the generator/rectifier/inverter on if you have 3xPowerwalls, all at say 30% charge and kick the gen off at say 80% - I just don’t see where the issue resides. If I understand the powerwall system, so long as you have less than 7.6kw of solar per powerwall, if your solar inverters (in this example, enphase microinverters) are connected to solar panels, the power walls will charge from them.

[solardreamer]

No need to let the smoke out. LOL!

I only use 48v rectifiers to power gear, not to do this stuff. I am just curious, if you kick the generator/rectifier/inverter on if you have 3xPowerwalls, all at say 30% charge and kick the gen off at say 80% - I just don’t see where the issue resides. If I understand the powerwall system, so long as you have less than 7.6kw of solar per powerwall, if your solar inverters (in this example, enphase microinverters) are connected to solar panels, the power walls will charge from them.

I remember seeing this talked about in Tesla forums and some have tested on small scale. Tests did work but pretty inefficient charging with AC (gen)->DC(PSU)->AC(PV inverter)->DC(powerwall) conversion losses especially in the DC PSU's.

[Blacroix]

I can def imagine the lack of efficiency. I just dream of a home with a bunch of powerwalls and a roof of solar, but dislike the generator tie in method for the very rare scenario the power is out long enough to deplete the batteries (power goes out, backup gen then kicks in and we get to reset all the clocks... LOL). Maybe I am just lazy, but everything blipping at night and waking me up is just annoying. I like in Texas, so just dealt with the recent grid fiasco. Thankfully, I have a generator then I put a nat gas conversion kit on, so we had power and heat. Evaluating the options should we move homes in the future.

It’s very nice to know folks have tried this though.

[solardreamer]

I can def imagine the lack of efficiency. I just dream of a home with a bunch of powerwalls and a roof of solar, but dislike the generator tie in method for the very rare scenario the power is out long enough to deplete the batteries (power goes out, backup gen then kicks in and we get to reset all the clocks... LOL). Maybe I am just lazy, but everything blipping at night and waking me up is just annoying. I like in Texas, so just dealt with the recent grid fiasco. Thankfully, I have a generator then I put a nat gas conversion kit on, so we had power and heat. Evaluating the options should we move homes in the future.

It’s very nice to know folks have tried this though.

I appreciate and share the frustration but the idea is also not very practical in that DC wiring to microinverters or optimizers on roof tops are not easy to access. In general, generators are still much more practical emergency backup power solution than home batteries especially restrictive ones like powerwall. I read that some Texas powerwall owners had full batteries when the outages started so they couldn't use solar power for loads (this is a "feature" in most home batteries) during the day and by they time they used enough of the battery power to activate solar power the sun was already way down and not enough to charge the batteries. Powerwall not allowing direct battery charging from generators is a serious limitation for these situations. So, the powerwall owners wasted solar power and didn't have enough battery power to even start up again for the next day. Like you I have natural gas (actually tri-fuel) generator and for emergency backup power its simplicity is hard to beat.

[Ampster]

Indeed the limitation of the Powerall not having a generator port as a backup may have been a frustration for some who were caught unsuspecting. The Powerwall users that did weather the storm without depleting their Powerwalls quickly rationed their power usage so they had enough power to get through the night until the next day when the sun could charge the Powerwalls again. I even heard one account of a user that did supplement his house loads with a generator to get through the night and therefore did not deplete their Powerwall so it was ready to charge from the sun in the morning. The Powerwall has a weakness in that it cannot reboot if it is depleted and has no AC grid to reboot from. Generator input is generally not clean enough to do that. That is one of the reasons we don't see an Powerwalls running off grid set ups.

[RottenMutt]

enphase has a generator input for their battery system, but it isn't activated yet. my guess they are waiting for this "injector" to release... so stay tuned.

[Blacroix]

The more I read, the more I dislike the AC coupled Tesla Powerwalls. I really like what I am reading about The Sol-Ark 12k. I could see two of them in parallel with a nice big batt bank, solar and a backup gen.

[Ampster]

The more I read, the more I dislike the AC coupled Tesla Powerwalls. I really like what I am reading about The Sol-Ark 12k. I could see two of them in parallel with a nice big batt bank, solar and a backup gen.

Three years ago had a reservation on a Powerwall but the limitation for me was that I only needed 5kW of inverter but wanted a lot more kWhs of batteries. At the time the SolArk was not on the market so i opted for the Outback Skybox. I now have 42 kWh of LFP batteries. Since that time I have heard good things from users on other forums about the SolArk.

[solardreamer]

The more I read, the more I dislike the AC coupled Tesla Powerwalls. I really like what I am reading about The Sol-Ark 12k. I could see two of them in parallel with a nice big batt bank, solar and a backup gen.

Sol-Ark is certainly more flexible than Tesla but so is Schneider/Magnum/Outback that have been around a long time. However, even non-Powerwall hybrid systems have the "feature" that will disable solar when batteries are full.

[solardreamer]

enphase has a generator input for their battery system, but it isn't activated yet. my guess they are waiting for this "injector" to release... so stay tuned.

Your guess is as good as any. It's been vaporware for years now that I have stopped following it.