Faster charging with higher amperage?

Hi everyone,

I just purchased a 2013 Leaf SL that supports rapid charging. So far I've been using the trickle charger. I'm looking at installing an L2 charger, and was looking at 6.6-7.2KW charging stations from Blink and Siemens. Both are 30A units that require a 40A breaker.

No problems there.

Then I read that higher amperage means even faster charge times. So in theory if I went with a ClipperCreek 48A unit that requires a 60A breaker, it will charge faster than the cheaper 30A units out there.

With 6.6Kw being the max wattage of the Leaf's charger, will higher amperage from the charging unit make a meaningful difference?

Thanks! Love my new Leaf!

No, the limiting factor here is the max power that the charger in your Leaf can use to recharge the battery: 6.6 KW. Supplying it with more than that won't make a difference, so get the EVSE (just a fancy power switch, really) that requires the 40A breaker.

If you're thinking of buying a Tesla in the near future, I guess you could prepare for a charger that can use 10KW by getting an EVSE that can supply the corresponding current, or, as a compromise, just the 60A breaker + appropriate wiring, since those are a pain to redo later and won't cost too much more.

The reason I ask:

A 5v usb charger at .5 Amps takes 7 hours to fully charge my phone.
A 5v usb charger at 2.2 Amps takes 2 hours

The voltage is the same. So a 6.6kw charger doesn't seem to make reference for the number of amps it supports.

I've also seen 6.6kw chargers that seem to run with 20 amps. The indicated charging time for EVs seems longer than those at 30 amp.

adriaanm said:

No, the limiting factor here is the max power that the charger in your Leaf can use to recharge the battery: 6.6 KW. Supplying it with more than that won't make a difference, so get the EVSE (just a fancy power switch, really) that requires the 40A breaker.

If you're thinking of buying a Tesla in the near future, I guess you could prepare for a charger that can use 10KW by getting an EVSE that can supply the corresponding current, or, as a compromise, just the 60A breaker + appropriate wiring, since those are a pain to redo later and won't cost too much more.

Click to expand...

Correct.

OP should understand the difference between the EVSE (what he's looking for) for the charger, which is on-board the car for L1 and L2 AC charging. OP has used the word "charger" in many cases where he should've used EVSE.

See http://www.mynissanleaf.com/viewtopic.php?p=332668#p332668 and http://www.mynissanleaf.com/viewtopic.php?p=262630#p262630.

https://code.google.com/p/open-evse/wiki/J1772Basics and PDF at bottom of https://code.google.com/p/open-evse/downloads/listv has more info.

The charger for the LEAF is internal in the car. Thus the charger will draw what it needs, while negotiating/handshaking with the EVSE to insure that the car does not overload the EVSE. The MOST the LEAF will draw is 6.6kw, which at 240v is 27.5 amps, which is exactly what mine draws on the EVSE, when measured with a clamp amp meter.

If you have a lesser amperage EVSE, it will handshake with the car so that the car doesn't overload it. An EVSE is nothing more than a smart switch, it makes sure the car will not overload it, it constantly checks for current leakage (GFCI) and shuts off if it detects current leakage that can kill someone, but resets up to 4 times in an hour before quitting for good, and also it checks for a ground circuit to the circuit breaker panel (all plug in and many hardwire EVSEs).

There are many good EVSEs on the market, the cheapest I've found (and what I am using) is a GE from Home Depot for $399. It is however, hardwire only (by code and UL qualification). There are several other good units on the market for under $600 or so.

20 amp level 2 EVSE units output at 16 amps (max of 80% of input amps by code) and these units, again, handshake with the car's charger to insure they are not overloaded, thus the car will be charging at 16 amps times 240 volts equals 3.8kw. (volts times amps equals watts, or watts divided by volts equals amps, or watts divided by amps equals volts. If you know two, you can figure the third).

paulnptld said:

The reason I ask:

A 5v usb charger at .5 Amps takes 7 hours to fully charge my phone.
A 5v usb charger at 2.2 Amps takes 2 hours

The voltage is the same. So a 6.6kw charger doesn't seem to make reference for the number of amps it supports.

I've also seen 6.6kw chargers that seem to run with 20 amps. The indicated charging time for EVs seems longer than those at 30 amp.

Click to expand...

Watts = Volts * Amps -- When comparing, we all know the voltage is 240v, so we don't mention it.

20a * 240v = 4800W = 4.8kW
30a * 240v = 7200W = 7.2kW
27.5a * 240v = 6600W = 6.6kW

Your LEAF will charge the max of what the EVSE can supply and 6.6kW (the max the on-board charger can use).

Very helpful. Thanks so much.

As others have said, the car's internal charger sets the amps and as long as the EVSE can supply the requires current you are gold. A 2012 Leaf at L2 240 V will draw 16A from a 20A eves. it will draw the same current from a 80A EVSE ( the spec max). As long as the EVSE can supply the requested current the rest is ignored.

My Mercedes B Class would charge at 30A from a 30A EVSE. Given at least 40A it will charge fully. AS long as the EVSE will supply 40A my car is happy. Given 50A, it will ignore the excess and still charge at 40A.