What's the maximum charging voltage?

[johnrhansen]

I just got a 16/32 volt buck/boost transformer, 1kva. I'm thinking it might help my charge wait time on road trips by raising the charging voltage just a bit. I know 240 is good, and that's the main thing I'm trying to do is to take the 208 volts from some places and bump it to 240. But what if i took the 240 and bumped it up to 272? Would that fry the leaf?

[mwalsh]

I just got a 16/32 volt buck/boost transformer, 1kva. I'm thinking it might help my charge wait time on road trips by raising the charging voltage just a bit. I know 240 is good, and that's the main thing I'm trying to do is to take the 208 volts from some places and bump it to 240. But what if i took the 240 and bumped it up to 272? Would that fry the leaf?

It would likely fry your upgraded EVSE. I talked to Ingineer Phil about a very similar scenario some time ago and he said it wasn't a good idea.

[johnrhansen]

I forgot to say. It would be after the evse. The evse would get the supply voltage.

[dhanson865]

I forgot to say. It would be after the evse. The evse would get the supply voltage.

how are you going to boost voltage between the evse and the car? You are going to put a J1772 connector and inlet on the voltage booster?

And what EVSE are you using, the Bosch 30A or the evseupgrade?

I know my openevse doesn't have any problems with 245 volts at my house. I don't think I'd try anything over 250 volts.

[TomT]

A terrible and very dangerous idea, if it even worked at all...

I forgot to say. It would be after the evse. The evse would get the supply voltage.

[johnrhansen]

It's not a terrible idea to raise 208 volts to 240. It's designed for 240. but anything past that I am dubious about, and this is why I asked.

[dhanson865]

It's not a terrible idea to raise 208 volts to 240. It's designed for 240. but anything past that I am dubious about, and this is why I asked.

It's not designed to be between the evse and the car though. By design you should be upping the voltage from the wall to the evse.

If you are trying to raise the voltage of a public evse where no wall outlet is involved then you are bypassing safeguards in the evse or at the least have to build a very complicated pass through setup.

[TomT]

No, but it is a terrible idea to put the transformer AFTER the EVSE...

It's not a terrible idea to raise 208 volts to 240. It's designed for 240. but anything past that I am dubious about, and this is why I asked.

[pchilds]

On the LEAF there is nothing to gain going above 240 volts, on Tesla based vehicles, 265 volts give you the fastest charge.

[GerryAZ]

If the EVSE has a high enough current limit, there is no difference in charging time between 208 and 240 volts because the onboard charger will draw more current to compensate for the lower voltage. With a 3.3 kW onboard charger, there will be no difference in charging time as long as the EVSE allows at least 18 amperes. With a 30-ampere EVSE and 6 kW onboard charger, charging times will be slightly less at 240 volts because the charger will draw about 27 amperes at 240 and 30 amperes (current limit of EVSE) at 208 (6480 W input at 240 volts and 6240 W input at 208 volts). The difference in time is only about 4 percent. If the EVSE has a lower current limit, then the charging time would be 13 percent less at 240 vs. 208 volts (208/240=0.867).

Gerry