Using V2L as alternative to generator in Sonnen ECO system

I live in Maine, USA. I have a Sonnen ECO battery system (max 16kwh, currently at 12kwh) with PV. For the most part, it works great. The one part of the design I am not crazy about is . . . If the PV panels are covered with snow and the grid is out, I only have available the power left in the battery system. I have compensated for this by have an external plug that I can hook a generator to to charge the batteries if, in this situation, the batteries get too low.

I am exploring purchasing an EV and one of the things I am wondering is whether I can use V2L technology (provided the EV supports) to plug in my EV to recharge my Sonnen battery array in the situation I mentioned above. Would this work?

The reason this seems preferable to me as opposed to V2G or V2H is that I would not have to change my system or my relation with the power company (I would also avoid needing to buy a bi-directional EV charger.


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Hi Fran, if you are already using a plug-in generator to charge the batteries, then there is no reason why you couldn’t use a vehicle with V2L in place of the generator. The only issue may be with the power rating of the generator compared to the EV. I’m assuming your generator is rated at 5 to 8kVA, while most EV’s with V2L are limited to 3.5kW (4kVA).

A better option, as explained in the V2L article, is to use an AC changeover switch to directly power the backup loads via the EV. This would be much less complicated and reduces the risk of potential issues using the EV with the Sonnen ECO system.

The biggest concern with using any alternative power source (Generator or EV) to charge a battery in a Hybrid solar system such as the Sonnen ECO, is the potential for the Hybrid system to back feed (or export) excess solar into the source causing irreversible damage.

Thank you for your response.

While not fool-proof, it seems it could be relatively safe to charge the Sonnen battery system and power my house if:

  • I am definitively running in off-grid mode. The Sonnen system “throws the switch” when grid power is unavailable and only throws it back when grid power is detected. If the battery has declined (e.g. say 30% remaining) and PV generation not producing (e.g. due to snow cover), I then throw the main switch to grid to make sure no backfeed to grid occurs.
  • I flick off the breaker associated with the SolarEdge inverter connected to my PV array. This should disallow PV as a source of backfeed.
  • I keep usage in house to under whatever the V2L EV rating is. The excess would then be used to charge the battery.
  • I disconnect the EV once Sonnen battery is charged and flick all the switches to their starting positions,.

Is this sound thinking? Am I missing something?

Hi Fran,

Yes, if you are careful and follow the steps you listed, then I think you should have no problem using an EV with a V2L rating of at least 15A (3.3kW). You may have difficulties with an alternative power source rated less than this as the Sonnen ECO system requires at least 3.3kW, depending on which model you have.

Do you have the latest Gen 3 Sonnon ECO or an older one? The older models were only rated at 3.3kW, so you should be fine. The newer models are more powerful and could potentially draw overload the EV when it tries to charge the battery. Can you set the charge rating using the Sonnen App?

Thanks again for responding.

I have a Gen 2. The Sonnen app does not show me the settings (that is reserved for the authorized installer) so I sent a query to support and will report back when I hear.

I do not have a sub-board with essential loads. The Sonnen is set up as a whole house backup. With that in mind, I don’t think the transfer switch mentioned in the V2L article is applicable. Am I reading that correctly? Or are there advantages to setting that up?

There is really only one non-discretionary load and that is the electric hot water heater. If I am home in a storm or I am away for more than a day or two, I shut that off at the circuit board. I then just use the stove judiciously and avoid the dryer, etc.


Here is a bit more information from Sonnen support:
“The generator must meet the below specifications in order to operate with the sonnen:

  • Max 12kw (a 50A OCPD must be installed between the sonnen and generator if gen > 12kW in size)
  • 240V split phase
  • Pure Sine Wave output
  • 4 wire: L1, L2, Neutral, Ground
  • Manual or 2-wire autostart feature
    • If autostart it must use one of these three methods:
      • 12V two wire
      • 24V two wire
      • two wire dry contact
  • < 5% Total Harmonic Distortion (THD)

As far as for an EV, the sonnen is currently only able to support a level 1 charger.

Level 1 charger (L1) is the slowest type of charging equipment. L1 chargers plug directly into a standard 120 volt (V) AC outlet supplying an average power output of 1.3 kW to 2.4 kW. I was informed that sonnen’s can only support L1 charging.

I think the wording about “Level 1 Charger” is around using the Sonnen to charge an EV.

Sonnen says they do not currently support charging from an EV but I am still trying to figure out if this is a technical limitation or just a support position. The generator I use with the Sonnen is portable and complies with their specifications. If an EV AC output is in that same range, I can’t see why V2L from an EV would not work.

Any thoughts?

There is no minimum generator size specified, but it does state that it needs to be a 240V split phase supply so I’m not sure how it would go with only 1 phase (240V). Most countries, like here in Australia, have only one phase so it wouldn’t be a problem. :thinking:

Is your current portable generator split phase?

Yes, a Level 1 charger is just an EV charger. Level 1 chargers are usually rated at 10A (2.4kW)

Hi Jason,

This is the generator that I bought from Revision . . . the approved installer of my Sonnen system . . .
[]( series/0196610-a-gp5500.pdf?ext=.pdf)

The model number is 5939-5. It is single phase with an AC rated output running watts of 5500 watts and maximum starting output of 6875 watts.

I use the twist lock output to connect to the external plug at my house that connects to the Sonnen system. That output is 25A. 120v/240v

I would imagine that if this is approved by Sonnen then there is no technical reason that an EV output plug that is 25A 120v/240v and has a maximum output of 5500 or less shouldn’t work.

Make sense?

@arpeggiotech, true. However, the problem is I don’t know of any EVs with V2L that have a 120v/240V output. They generally only have either 120v or 240V, not both (split phase).