V2B (Vehicle 2 Battery) as a V2H alternative – Klein Erna has an idea and a question

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Vehicle 2 Battery (V2B isn’t actually a term. I made it up. Perhaps there’s a good reason for that too.)

On a longer drive in my new electric car with V2L (Vehicle 2 Load), I did a bit of thinking, like “little old me”.

If I’m already charging my MultiPlus 2 48/3000/35-32 GX with 2x Pylontech either via PV or from the mains on the AC side, why not also use the car’s 84 kWh?

>I’m not talking about charging for free at IKEA and then filling up my 10 kWh battery — that would be too much effort for me. But in winter, with the dynamic prices from Tibber, I often pay €1 or more. At the same time, I can no longer get the Pylontech fully charged from the PV system.

So my idea is this: when there’s effectively no excess PV available, I could use the wallbox to charge, based on the price, say 11 kWh into the car and 1.5 kWh into the Pylontech for one hour a day at a cheap rate, and then use the car to charge the Pylontech for several hours.

So that’s what “little old me” came up with.

Electric car V2L → Schuko plug → AC In on the MultiPlus

Of course, this won’t work as it stands, because the mains supply is also connected to the AC In, and both sources can’t be used together.

So there would also need to be a changeover switch BEFORE the AC In, to switch between the mains supply and the electric car’s V2L. The changeover switch must mechanically or electrically prevent both sources from being connected at the same time (2-pole, for L and N).

A Victron VE Transfer Switch should then be possible/necessary, right? But at over €200, it would never pay for itself.

Are there any alternatives, particularly mechanical ones?

Has anyone already implemented this and could tell me how / with what?
Or would you say — keep well away. Should “little old me” not be having thoughts like these :slight_smile:

Thanks for the input/feedback

Jörg

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The Multi would probably also still need to be reprogrammed, because it won’t accept V2L as the “grid”.

For the changeover switch, I’d probably use a Hager SFB 225.

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Thanks for the quick feedback.

So Little Erna can keep “thinking”.

As far as I know, V2L in my EV generates its own 230 V network.

I’ll take a look at the Hager SFB 225 and Hager SFT 240.

I’m curious to see whether anyone has already built or cobbled together something like this.

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We discussed the topic of „V2B“ or V2H some time ago … I think it was even on the old forum … and it ultimately came down to using a separate charger. With a shunt in the DC line, it could then also be represented graphically as an AC or DC generator.

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Yes, I have something like that in operation with an EV6. In that case, though, I used an old MP2 to connect the V2L port. A normal charger or power supply would work here too. An MP2 with a grid code compliant with VDE-ARN-4105 won’t switch the car through (even if your changeover device works). So you’ll either have to use a charger or reprogramme your existing MP2 every time.

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Hello,

I’ve built and tested the whole setup for someone before.

It doesn’t work with just a changeover switch, because the Multi only accepts the vehicle’s power when it is operating without a GridCode.

That’s why, in this case, an additional MultiPlus was purchased and connected to the Cerbo via a USB-MK3. It then had a Type 2 plug as its connection.

The whole “logic” behind it was programmed in Node-RED.

The setup was operated exactly as you want it for one winter, and then dismantled again.

  • Too much energy loss: AC grid → DC car battery → AC grid
  • Having two plugs — one for charging and one for discharging — was too impractical (automatic switching was possible, but it was no longer within budget)
  • Too expensive (MultiPlus, MK3, fuse, cables, etc.)
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And if you don’t want to overcomplicate things, you can also use an MP2 connected only to your car on the AC-In side and to your Pylontech batteries on the DC side, controlled via MK3 by your Cerbo. You’ll just need to configure the voltage settings on the MP2. :grinning_face:

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Thanks for the feedback.

Well, our little Erna has certainly come up with something.

But “thought of” isn’t the same as “done”.

An extra charger for the Pylontech, or even a second MP2, makes it very uneconomical after all, since there’s no way to recoup the €200–400 cost, including the wiring. And even if you factor in a bit of tech-freak money because Erna wants something like that, it would still involve the extra effort, and you’d only use it ten times.

So I’ll have to wait for a V2H solution with a new wallbox for my EV6 after all.

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Perhaps simply increasing the size of the home battery a little and making its use dependent on the electricity price would already help avoid drawing power from the grid when prices are high. Pylontech isn’t exactly ideal in terms of value for money, of course.

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However, in my opinion, the problem is the single MultiPlus-II 3000, as it can only charge the battery at around 1.7 kW… it takes far too long to charge the battery, since electricity prices are generally only rock-bottom for a short time.

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Exactly, that’s the point. I can enable dynamic charging, of course. But then I only get about 2 kWh into it.

Increasing the battery capacity doesn’t really help either. I can’t even properly charge the 10 kWh battery to full in winter.

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Perhaps it would be easier to look for a normal electricity tariff … I have one, for example … they supply electricity at 22.7 ct/kWh…

Then I don’t need to worry about it…

And a simpler solution might be to connect your car directly to a switched-off phase of the house … but that depends on the appliances drawing power … and on whether it’s permitted ?? No idea ,O)))) Or simply connect a large power consumer directly to the car..

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Since an EV6 supplies a maximum of 16 A via V2L, which is already quite a lot, that may not be a suitable approach either. Depending on what’s connected to that phase and how everyone in the household goes about switching things on and off… :wink:

14

You can connect a TelKo power supply to the V2L port and use it to charge the battery directly via the DC bus.
You’ll then also need a SmartShunt to integrate the “DC generator” into the system.

But are the cost of buying the components and the time needed to set up the controls really worthwhile for 9 kWh/day, potentially saving 10 ct/kWh each time?

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Basically, I would also implement it using a blue CEE camping plug-and-socket connector (wall-mounted, not a trailing connection), followed by the power supply, MP2 and battery.

But is it really always just about whether it’s “worth it” or “cheaper”?

It’s also about pushing fossil-fuel generators out of the grid (during the transition period) — especially when an electricity-driven heating system (i.e. an air-to-water heat pump) is used at home.

However, this only works if the alternative source is 100% renewable energy.

So-called dynamic/flexible tariffs are not a solution, because the sun doesn’t shine at night (there may be wind in the north), and they merely feed the profits of gas-fired power plant operators.

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Good morning,

I use a 24V 3K Multi in charger only mode, the grid input limit from the Multi on 11A, that’s all, the car can deliver 3500W, so it never overheats the car inverter nor the Multi.

I use it only for emergencies.

Regards, Jeroen.