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Amps for a new charger ?

Posted: Fri Dec 04, 2015 8:44 am
by wildviking
I am doing a new install in my garage for a new 2016 leaf . I have a 220 30 amp welding circuit available to use but I was wonder from all the experts here is that the best or should I have the electrician put in a new bigger circuit ? Kind of confused as the the best way to go for the quickest charge on the new leaf. Sorry if this is a lame question I tried to search the answer but wound up getting more confused ..

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 9:15 am
by pkulak
30 amps isn't going to be enough to charge your Leaf as fast as it can. Technically, that's 5.7 KW, and the Leaf will draw 6.6 if you let it. So, you'd have to get an EVSE that can be set to 30 amps, or just use a 20 amp one. That'll be just fine, of course, but ideally you want a 40-amp circuit. The wiring may actually support 40 amps, so it could just be a matter of swapping the breaker and the plug. And you don't need neutral, so even if it's only 3-wire, you're still good.

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 9:17 am
by pncguy
First, ask yourself if you want to "future proof" your installation. If you do, then you likely want to get a circuit that can handle a higher current.

If you don't, then ask what your vehicles maximum charging capacity is. Hint: if you have an SV or an SL, it is 6.6kW. If you have an S, it is either 3.6 or 6.6kW.

If your circuit is 220V, 30A, then you first have to understand that the 30A rating is not for a continuous draw. The rating must be 125% of the maximum continuous current draw. So to go the other way, you calculate 30A/1.25 = 24A. If the voltage available at the car is truly 220V, then the power that you can deliver is 220V x 24A = 5.28kW. (Note that you could only go to 6.6kW/240V = 27.5A for your vehicle, anyway...)

So, if you truly want to maximize your charging speed, you'll need to upgrade.

But first I would suggest living with your L1 charging to see how much speed you really need. My family has decided that we do want the full 6.6kW rate allowed because we want the flexibility to charge to 100%, use the full charge in the morning, recharge, and use the full charge to go out at night. You can't do that with normal L1. L1 charging is typically 12Ax120V = 1.44kW. You may find that the 1.44kW it fine for your needs, or you may find that getting an EVSE that will deliver 24A is just fine, too.

Given that you already have a plug, I might investigate an EVSE that can deliver 30A if you want it, but also has a feature that allows you to turn down the allowed current draw to 24A. That way, if you want a faster charge, your EVSE can do it, but you'll need to install a bigger circuit.

[And I just read the post that got there before I finished this one - yeah, you might check to see if the wiring can already handle 40A. Then you're good to go with a 30A EVSE.]

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 9:21 am
by pncguy
pkulak wrote:30 amps isn't going to be enough to charge your Leaf as fast as it can. Technically, that's 5.7 KW


How did you calculate 5.7kW given a 220V, 30A rated circuit?

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 9:39 am
by TimLee
pncguy wrote:
pkulak wrote:30 amps isn't going to be enough to charge your Leaf as fast as it can. Technically, that's 5.7 KW


How did you calculate 5.7kW given a 220V, 30A rated circuit?

Continuous load cannot be more than 80% of the breaker rating.
And it is nominally 240V, not 220V.

30 times 0.8 times 240 is 5.7 kW.

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 10:22 am
by pncguy
OP, did you get enough info to answer your question? There are a lot of different numbers to toss around (220V vs 240V vs 208V, 30A, 24A, etc.) but I think we put all the info above to answer your question.

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 2:24 pm
by wmcbrine
pkulak wrote:30 amps isn't going to be enough to charge your Leaf as fast as it can.

Pretty close, though. 24 amps continuous vs. 27.5. I'd save the money.

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 2:42 pm
by Valdemar
wmcbrine wrote:
pkulak wrote:30 amps isn't going to be enough to charge your Leaf as fast as it can.

Pretty close, though. 24 amps continuous vs. 27.5. I'd save the money.


+1. Unless the OP has a very specific reason to be able to charge 10% faster on a regular basis. For overnight charging it mostly doesn't make any difference. A 24A EVSE is probably less expensive than a 30A one as well.

Re: Amps for a new charger ?

Posted: Fri Dec 04, 2015 3:38 pm
by LeftieBiker
First, virtually all US grid voltage is now 240 volts, not the old 220 standard, so more power is provided via the higher voltage. Second, the Leaf charges at 27.5 amps max, so a 30 amp circuit will come close, as noted above. I would definitely not upgrade that circuit unless I really needed to charge the car at 100% of its possible charging speed, as long as the wiring and outlet are in good shape. Third, you can put an 'adjustable' 14-30/14-50 plug on the EVSE (you can leave off the Neutral prong, as it isn't used in an EVSE circuit), allowing you to take it with you and charge at RV parks, if that's a possibility for you. You already have a wiring option that many of us envy.

Re: Amps for a new charger ?

Posted: Sat Dec 05, 2015 3:04 am
by RonDawg
If the OP can live with a 6 hour turnaround time vs. 5, I would stick with what's already there and get a 24 amp EVSE like the Clipper Creek HCS-30 for $565. Yes it's the same price as the 32 amp HCS-40 but there's no added cost for upgrading the wiring and changing out the breaker.

If the OP can live with an 8 hour turnaround time, the 20 amp LCS-25 is almost $100 less.

These figures assume a 24 kWH battery that is fully drained. If you have a 30 kWH battery then add 25% to the charging times.