What's the maximum charging voltage?

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johnrhansen

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Joined
Aug 12, 2013
Messages
1,100
Location
Seattle, WA
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?
 
johnrhansen said:
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 said:
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.
 
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.
 
johnrhansen said:
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.
 
No, but it is a terrible idea to put the transformer AFTER the EVSE...

johnrhansen said:
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.
 
On the LEAF there is nothing to gain going above 240 volts, on Tesla based vehicles, 265 volts give you the fastest charge.
 
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
 
johnrhansen said:
what if you have a 50 amp EVSE? What's the most current the leaf can draw at 208 volts?

It would probably draw between 31 and 32 amperes if it has the 6 kW onboard charger, otherwise it would draw about 18 amperes for the 3.3 kW charger. It would draw a bit more to compensate if the voltage sags below 208.

Owner manual for 2015 lists maximum rated current at 32 amperes (if equipped with 6 kW charger) or 18 amperes (if equipped with 3.3 kW charger).

Gerry
 
kajol said:
I just got a 16/32 volt buck/help transformer, 1kva. I'm supposing it may enable my charge to hold up time on excursions by raising the charging voltage a tad. I realize 240 is great, and that is the primary concern I'm attempting to do is to take the 208 volts from certain spots and knock it to 240. In any case, imagine a scenario in which I took the 240 and knock it up to 272. Would that sear the leaf


The car doesn't care if you give it 208V or 240V. It'll draw 6.6kW and charge. It'll draw ~31A@208V and~27A@240V. I don't know what the max input voltage is for the charger, but I don't see any point or advantage to raising it above 240V, nor do I see any advantage to bumping to 240V from 208V.
1kVA is 1000W. You're going to decrease your charge wattage by 5600W with that little transformer.
 
kajol said:
I just got a 16/32 volt buck/help transformer, 1kva. I'm supposing it may enable my charge to hold up time on excursions by raising the charging voltage a tad. I realize 240 is great, and that is the primary concern I'm attempting to do is to take the 208 volts from certain spots and knock it to 240. In any case, imagine a scenario in which I took the 240 and knock it up to 272. Would that sear the leaf

Moderator - this user seems to simply be parroting previous posts as a pretense to putting their spam link out there.
 
91040 said:
^^^I reported the first two posts by kajol to the moderator the other day. Hopefully, they will act.

The spammer and his posts are now gone. I'm not going to bother deleting the quotes of the posts unless the authors request it - their posts would make no sense without the quotes. I did delete the link in the quotes.
 
Tsiah said:
kajol said:
I just got a 16/32 volt buck/help transformer, 1kva. I'm supposing it may enable my charge to hold up time on excursions by raising the charging voltage a tad. I realize 240 is great, and that is the primary concern I'm attempting to do is to take the 208 volts from certain spots and knock it to 240. In any case, imagine a scenario in which I took the 240 and knock it up to 272. Would that sear the leaf


The car doesn't care if you give it 208V or 240V. It'll draw 6.6kW and charge. It'll draw ~31A@208V and~27A@240V. I don't know what the max input voltage is for the charger, but I don't see any point or advantage to raising it above 240V, nor do I see any advantage to bumping to 240V from 208V.
1kVA is 1000W. You're going to decrease your charge wattage by 5600W with that little transformer.
This is totally incorrect, at least for both my '12 and '13 Leafs :)
My cars max out at either 16a(for the '12) or 27.5a(for the '13) so voltage makes a large difference for me AFA charging speed. It's my belief the 3.6kW or 6.6kW ratings are at maximum voltage or 240v, if you use 208v the Kw will be less. Now you Leaf may be different than mine but I know voltages and amps and know how my Leafs work(and have several EVSEs that display instantaneous amperage) :)
 
My 2011 would draw about 16 amperes at 240 volts at home and 18 amperes at 208 (usually about 212) volts at my workshop/garage. The 2015 draws about 27 amperes at 240 volts and 30 amperes at 212 volts. I suspect it would draw a little more (probably up to 32 amperes) if the voltage were lower. Therefore, as stated before, there is not much difference in charging rate unless EVSE current limit is reached.
 
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