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Powerwall 2 batery recharge with a generator?

Powerwall 2 batery recharge with a generator?

I am interested in installing a powerwall 2 but I want to know if a generator can be installed as an alternative method of charging the battery.

vpadillapr | 5 February, 2018

02/05/18

FloridaDave | 10 February, 2018

Powerwalls are listed as backup generators themselves. Thats how you can have your power on during an outage with powerwalls and a PV system vs no power during a outage with PV only. So you will use a generator to charge your generator in order to power your house. Thats very wasteful.

psusi | 10 February, 2018

It isn't a generator; its a battery. And when the choice is between having no power ( the battery will only last a few hours ), and running a generator, the choice is clear.

michael_kaatsch | 12 February, 2018

Can a Powerwall be integrated into an existing off grid system? Even if you had to insert the Powerwall between the existing inverter and the main electrical panel to the house, this assumes the inverter on the Powerwall is sufficient?
Would a 4048 inverter be enough to charge the Powerwall?

murat.topcu | 20 February, 2018

"Can a Powerwall be integrated into an existing off grid system?"

Great quations. I want to integrate in our company Powerwall(s) into an existing grid system to charge them at night or at times, when the waether is not that great.

Steve1081 | 20 February, 2018

Here is the answer:

Generator Integration

How would Powerwall be installed with a backup generator?
Powerwall can be added to an existing system that has solar panels and a backup generator connected with an external Automatic Transfer Switch (ATS) or Manual Transfer Switch (MTS). Powerwall is installed between the electrical service entrance and the transfer switch, where it charges from solar while the grid is operational.

How does Powerwall work with an existing backup generator?
In an outage, Powerwall responds immediately and provides backup power before the ATS is able to detect the outage. The ATS switches to the generator only when the Powerwall state of charge drops below a set threshold, or if loads exceed Powerwall's maximum output. When grid power returns, the ATS turns off the generator and Powerwall can again charge from solar. If Powerwall is installed with an MTS, manual operation of the switch is required to power the home with the generator.

Can my generator charge Powerwall?
Powerwall does not currently have the ability to charge from a generator. Please stay tuned for future updates.

Does Powerwall work with existing battery systems?
Powerwall does not currently have the ability to work with existing battery systems. Please stay tuned for future updates.

I have a wind turbine/hydro turbine. Can I charge Powerwall with it?
Powerwall does not currently integrate with other renewable generation equipment. Please stay tuned for future updates.

https://www.tesla.com/support/energy/learn/powerwall/generator-integration

Steve1081 | 20 February, 2018

It says "Stay Tuned" so hopefully they are working on the ability for Powerwall to be charged by a generator for off grid or power outage systems to improve efficiency vs just going 100% to the generator when the Powerwall / Solar can't keep up. In theory the powerwall(s) would allow for a smaller and more efficient generator by handling the demand spikes of large motors starting (AC, Well Pumps, Pool Pumps, etc.).

murat.topcu | 20 February, 2018

I found the answer:

https://www.tesla.com/support/energy/learn/powerwall/functionality

Can Powerwall charge from the grid?
When Powerwall is installed without solar, it can charge from the grid to support backup operation.

When Powerwall is installed with solar, it is not currently able to charge from the grid. Powerwall installations on new and existing solar systems are designed to qualify for the Federal Investment Tax Credit, which requires 100% charging from solar. Powerwall installations must also comply with rules around grid charging which vary by utility.

gballant4570 | 18 March, 2018

I think it's more regulations involved with tax incentives than ability to set things up that way. To qualify for the incentives, the battery must only be charged by solar. In the USA anyhow......

keckel2 | 26 March, 2018

I will be doing a backup generator in my installation. We get tropical weather and the grid can be down for weeks. I will also have solar but the risk of losing my PV in a storm is also pretty high. A Generac running Propane while not green will provide reliability for our highest probabaility risk. Now, the question. the Q&A talks about integrating generators and when the power wall fall below a threshold it will switch to the generator through the Auto switch. Great! What is the threshold? Can the Power wall signal the generator to start and warm up say 2 to 3 minutes before the load is shed to the generator? I have a generator at a remote cabin and it works by auto switch but power has to be lost for about a minute before the generator is signaled to start. It starts, warms up for about 2 minutes then connects to the load. So I have about 3 minutes without power. It would be difficult to time this exactly or by paralleling the generator then dropping the powerwall. I guess my question is how is the generator signaled except by loss of power? Follow on question, When grid power comes back on, the generator will disconnect, will the powerwall still operate ?

JerryLove | 27 March, 2018

I've got some similar questions and concerns. I am in hurricane territory. I'd like to be able to primarily use solar during an extended power outage; but there's no guarentee that production will meet demand.

So I need a generator.

In a perfect world, a low-power generator would be used to supplement the powerwall to prevent it from hitting zero charge... basically the generator would act like a solar panel (but one that was turned on and off based on criteria).

The alternative is a full-sized generator, at which point the math doesn't work for adding power-walls.

Eduardo.Delgado.PE | 16 January, 2019

How does Powerwall work with an existing backup generator?
On a previous post the note below was published but...how we can switch back to the solar system to resume charging if we have an extended utility outage such as with Hurricane Maria?
I am leaning to install Tesla at home but still need to clarify this point as we have also a 19KW Caterpillar Generator with an ATS.

Thanks!!!

"In an outage, Powerwall responds immediately and provides backup power before the ATS is able to detect the outage. The ATS switches to the generator only when the Powerwall state of charge drops below a set threshold, or if loads exceed Powerwall's maximum output. When grid power returns, the ATS turns off the generator and Powerwall can again charge from solar. If Powerwall is installed with an MTS, manual operation of the switch is required to power the home with the generator."

marc.e.marcsf | 3 February, 2019

My powerwall install happened about a year ago. I had the same questions about Solar charging, Wind turbine charging and gas generator charging. I could not get a straight answer out of anyone. It seems as gballant4570 and murat.topcu are pretty much on point.

However, after the install, it appears pretty simple to added a generator onto the AC feed from the solar panel (e.g. merge this AC feed with a generator feed) into the Powerwall Gateway. Then the Gateway wouldn’t know the difference whether it was Solar or Generator.

This could also be done at the Grid feed to the Gateway but this would be a bit more difficult since in my configuration it back feeds the grid when there’s surplus. This wouldn’t be possible to back feed a generator. However, if you branched the grid feed prior to the Gateway (e.g. put in a ATS or MTS there to have either Grid or Generator) then the generator could turn on when the Grid is down.

I’m also told (haven’t verified it yet) that the Powerwall/Gateway gets a signal when the powerwall is ‘empty’ or cannot supply the sufficient feed current. This could easily be tapped to turn on the Generator and trigger the ATS.

After all 110/220v 60Hz doesn’t have a difference whether it comes from the Grid or Wind Turbine or Solar. It’s all the same but on different feed legs into the GateWay.

DanielD | 19 October, 2019

Just saw this thread now as I'd hoped to charge my Powerwall from a generator.

I wanted to correct erroneous information above. "However, after the install, it appears pretty simple to [add] a generator onto the AC feed from the solar panel [... into the] Gateway. Then the Gateway wouldn't know the difference whether it was Solar or Generator."

That is not possible. Solar inverters (that are used with the Powerwall) are grid following. Grid following devices can't function unless they are tied to a grid. That's why adding a Powerwall to a grid-tie solar system enables off-grid operation: when the Gateway is disconnected from the utility, the Powerwalls go into grid-forming mode and the inverters can follow that.

AC gensets are grid forming. If you connect a grid forming device to a grid, disaster results. You'll destroy your genset and possibly a bunch of other things, all within a fraction of a second.

Also, grid-tie solar inverters support curtailment: if the Powerwall increases frequency (because the Powerwall is off grid and the battery is fully charged, but the inverters are producing power), the inverters will trip off. A genset will not.

In theory it is possible to take the DC output of a DC generator and connect that to a grid-following inverter. I have never seen anyone do this. If anyone has done it, please reply on this thread.

gregbrew | 19 October, 2019

Even if you could "fool" the TEG into thinking that the gas generator was the grid, it would be a very bad idea. Unlike the grid, a generator is not an energy "sink". All it would take is a momentary condition where the inverter tried to backfeed the "grid"...and it would destroy the generator and possibly the inverter with it.

Besides, in the USA, most utilities forbid the charging of Powerwalls from the grid, except in potential grid emergencies via the "Stormwatch" feature. So, the TEG wouldn't allow it anyway. Charging the PWs from the grid *is* allowed in some other countries. (Australia and Britain are two.) Hacking the TEG's firmware for US applications would probably be the only solution around that. I suspect that Tesla would frown upon that type of activity.

KTL | 29 October, 2019

Still no answer on what the "set threshold" is? When the battery loses grid power and is "low" can you set the % value of when the battery will kick on the backup generator? Letting it drain all the way down will cause a 3+ min outage while the generator turns on and produces load.. I don't want to charge the powerwall, I want to not have a disruption in power... allowing the generator to turn on 3 or so min. before full drain will solve that... but no one is able to answer? is the value settable on the powerwall?
This seems like an easy answer.. either it is useless to have a backup generator and you will still have the 3 min outage once the powerwall drains, or it is smart (or a manual setting on % battery remaining) enough to trigger the genertor startup process to not disrupt power... which is it?

"In an outage, Powerwall responds immediately and provides backup power before the ATS is able to detect the outage. The ATS switches to the generator only when the Powerwall state of charge drops below a ***set threshold*** (in the current web page this reads "low change") , or if loads exceed Powerwall's maximum output. When grid power returns, the ATS turns off the generator and Powerwall can again charge from solar. If Powerwall is installed with an MTS, manual operation of the switch is required to power the home with the generator."

Passion2Fly | 29 October, 2019

When connected to Solar, the TEG will do frequency shifting to control the solar inverter. The threshold is ~70% SOC. When the battery drops below, the solar inverter is turned on and the battery is recharging. When full, the TEG will turn off the solar inverter and supply the house from the battery.