Can I use EV charger as a 3ph dumpload off grid?

I have a big 3phase coupled off grid PV instalation. 20kWp +45kWh BYD batteries using SMA 3phase inverters.

Can i use the EV charger as dump load for excess generation? Will it work off grid?


I’m surprised no one has added anything to this thread.

What car are you planning to use? The 3-phase EVSE has some weirdness about charging single phase cars, so you might come acropper there.

How does your inverter handle out-of-balance phases?

Not being an EV expert, I wasn’t going to comment. However…

I think it all depends on what you want to achieve. If it’s a perfect balance, then from what others have written, the EV is likely to be unable to vary its charge rate sufficiently finely or frequently to follow other loads switching on and off. But if you have sufficient surplus capacity to have the EV as the primary dump load and (say) Robin’s Mk2 that’s able to follow and achieve a better (or even perfect) balance, then I see it as feasible and worth close investigation.

The inverter, if it’s feeding a normal house, will never have a fully balanced load anyway, so it will probably come down to the degree of imbalance that it can tolerate.

Can’t speak to the 3 phase bit, but you can use an OpenEVSE charge controller off grid.

You need to create a feed which you can use to represent the excess PV power and use that to control the charge rate. With a battery system it’s not very important to have fast response as you aren’t trying to minimise export.

I have a system with 14kW of PV, 19kWhr of storage and a nominla 8kW inverter charger and it works OK with OpenEVSE.

It does have some issues, the main one is that it starts charging at 30A, regardless of the amount of PV power available and sometimes keeps going at that rate for some time. Mostly that isn’t an issue, but if you get a situation with low PV and high demand from other loads the inverter can shut down.

It’s also quite slow to resume a high rate of charge after a period of low PV output. Last time I charged my car I disabled the rate control and just charge at the maximum rate. the PV system batteries had to supply a bit of energy to the car but the car charged in a reasonable time and the battery still recharged fully after the car had finished charging.