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Re: EVSE source current

Posted: Mon Jul 12, 2010 10:32 pm
by AndyH
I get that you'd prefer 120V/16A rather than 120V 12A. No worries there!

I really think it's important that we understand that neither the charger nor the EVSE should really care about either number per se - they're just random numbers on a scale between the 8A min and 80A max. The EVSE can dial-in a 10% duty cycle to signal 8A available just as easily as it can set a 50% duty cycle to signal 30A.

There should be no problem at all (ignoring EVSE warranty and possibly UL recognition) to hack the OEM L1 EVSE that's likely preset to 20% duty cycle for 12A and reset the duty cycle to about 27% to allow the charger to pull 16A.

My Chinese charger that auto dials from 85V to about 260V is pushing 21A into the battery from a standard 15 A circuit. I'll bet we can do the same with the Leaf's L1 unit if we want to hack it. ;)

It's all good!

Re: EVSE source current

Posted: Tue Jul 13, 2010 8:32 am
by garygid
Charger AC current Requirement Example:

An efficient charger with a 120v AC input, putting 21 amps into a 75 volt (21 cells x 3.5 volts = 73.5 volts) battery makes about (21 x 75 = 1575 watts) of DC output.

So, the (maybe 94%) efficient (probably "switching" type) charger might draw about 14 amps (120 x 14 = 1680 watts) from the AC lines?

And, perhaps a little less if one actually has 124v AC instead of 120v?

That might explain why a 15-amp breaker does not "pop" when doing "21-amp charging". :)

Maybe my numbers are not perfect, but the general idea still holds.

Having 16 amps "allowed" gives us an extra 33% over the power we "are allowed" with the 12-volt max limit. So, 20-hour charging would drop to about 15 hours, and a "half" charge of 10 hours would drop to only about 7.5 hours ... possibly suitable for really useful 120v charging while at work.

Re: EVSE source current

Posted: Tue Jul 13, 2010 8:52 am
by LTLFTcomposite
Here's something to think about... the 120 volt cord plugs into the 1772 connector right? Is there a counterpart to that for cars being sold in Europe where 220 is the norm? I wonder if the on board charger is voltage sensing.. ie same thing for both Europe and US.

Re: EVSE source current

Posted: Tue Jul 13, 2010 9:11 am
by garygid
Yes, it appears that the "included" EVSE for the UK will be a plugin 240 volt (Level 2) portable unit, probably set for something like 14 or 15 amps, whatever is normally available their "standard" wall socket.

Yes, it would be nice to get one to "evaluate" here!

If anybody locates a source, please let us know.

Re: EVSE source current

Posted: Tue Jul 13, 2010 9:19 am
by LTLFTcomposite
garygid wrote:Yes, it appears that the "included" EVSE for the UK will be a plugin 240 volt (Level 2) portable unit, probably set for something like 14 or 15 amps, whatever is normally available their "standard" wall socket.

Yes, it would be nice to get one to "evaluate" here!

If anybody locates a source, please let us know.
The 120 volt cord for the US is not an "EVSE" per se, right? Basically just a cord with a GFI?

Re: EVSE source current

Posted: Tue Jul 13, 2010 10:00 am
by LEAFer
LTLFTcomposite wrote:The 120 volt cord for the US is not an "EVSE" per se, right? Basically just a cord with a GFI?
No ... I was confused about that too, because that's how the Tesla Roadster MC120 works. For Volt and LEAF it's apparently a "real" EVSE with pilot signal.
But back to what you were saying above ... is it V-sensitive ? Or more specifically, is the US version Voltage sensitive ? What if you just changed the NEMA 5-15P/5-20P to NEMA 6-20P and run it at 240V :twisted: ?
Would you then be able to charge at 240V/12A = 2.88kW ? 8-) In half the time ?
( I don't give up easily ... )

Re: EVSE source current

Posted: Tue Jul 13, 2010 10:16 am
by LTLFTcomposite
LEAFer wrote:
LTLFTcomposite wrote:The 120 volt cord for the US is not an "EVSE" per se, right? Basically just a cord with a GFI?
No ... I was confused about that too, because that's how the Tesla Roadster MC120 works. For Volt and LEAF it's apparently a "real" EVSE with pilot signal.
But back to what you were saying above ... is it V-sensitive ? Or more specifically, is the US version Voltage sensitive ? What if you just changed the NEMA 5-15P/5-20P to NEMA 6-20P and run it at 240V :twisted: ?
Would you then be able to charge at 240V/12A = 2.88kW ? 8-) In half the time ?
( I don't give up easily ... )
not to mention if you have a dedicated 120v 20A receptacle you could convert it to 240V just by changing to a double pole breaker

Re: EVSE source current

Posted: Tue Jul 13, 2010 10:25 am
by LEAFer
LTLFTcomposite wrote:not to mention if you have a dedicated 120v 20A receptacle you could convert it to 240V just by changing to a double pole breaker
Yes, but I wouldn't want to do that with a 120V NEMA 5-15/20 receptacle ... it WILL cause accidents. So, converting to the NEMA 6 series (which is 240volts) will prevent that. But, of course, in addition you would do as you said, "convert" the 20A dedicated (only one outlet) circuit from a single to double-pole breaker (and watch the wiring hot-hot-ground when you replace the plug at the end of the EVSE).

Any expert here ... agree this would work ?

(Edit: to keep the EVSE unmodified, could make an adapter (or pigtail) instead (from NEMA 5-15R to NEMA 6-20P.)

Re: EVSE source current

Posted: Tue Jul 13, 2010 10:43 am
by Bicster
Or as I suggested in another thread... get the 230V (Europe) portable EVSE from a European Nissan dealer, replace the plug on the end, and use it in the US. I doubt very much that the line frequency will matter.

If the US-spec portable EVSE turns out to be 240V-tolerant, so much the better, but it will still only draw 12A.

Maybe if the replacement L1 EVSE's are cheap enough, they can be hacked by replacing some of the guts. Or just lobotomized as a source for the charging cable and connector...

A homebrew solution will look more attractive if the connectors can be sourced easily. I'm in for a few if they're cheap enough. I have a fully licensed copy of Cadsoft Eagle that I can dust off if necessary :)

Re: EVSE source current

Posted: Tue Jul 13, 2010 10:50 am
by evnow
Or get it from Japan - where nodoubt it will be available earlier. There are places like PriceJapan.com which can sell you almost anything from Japan for a 5% margin on the lowest quoated price. I've done that for home theatre related stuff - not sure about auto.