Nissan Leaf - Charging.

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acmotor
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Post by acmotor » Tue, 27 Aug 2013, 16:31

Good question.

Part of the answer may be that the EV battery pack is isolated and monitored from the EV earth.
Feeding it with a non isolated (from AC mains) DC power source would result in an earth fault error and the EV disconnect the charging itself. i.e. a bad boy charger ( directly rectified mains) would not work and without that earth fault monitoring, the EV body could become live or blow a big fuse somewhere.

TJ, your CHAdeMO would have DC earth fault monitoring in itself, in addition to the EV's monitoring ?
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Post by coulomb » Tue, 27 Aug 2013, 18:36

PlanB wrote: Why the mandated isolation xformer? An earthed 3 phase motor doesn't need one, nor does the VFD.

I think it's because an EV has capacitive coupling to the (usually) metal chassis. A non-isolated HF switch mode power supply would have high frequency square waves between windings and chassis. You could conduct a lot of that away through the earth lead, but they prefer no current at all through the earth lead (except briefly in a fault condition to clear a breaker or RCD). Inductance in the earth lead would mean that there would still be some bite to the metal in many circumstances.

[ Edit: this was not my best thought-through post. It's basically shot down in the next 4 posts. ]


DC motors with their brush dust would be an extra problem.
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Post by weber » Tue, 27 Aug 2013, 20:45

coulomb wrote:I think it's because an EV has capacitive coupling to the (usually) metal chassis. A non-isolated HF switch mode power supply would have high frequency square waves between windings and chassis. You could conduct a lot of that away through the earth lead, but they prefer no current at all through the earth lead (except briefly in a fault condition to clear a breaker or RCD). Inductance in the earth lead would mean that there would still be some bite to the metal in many circumstances.

DC motors with their brush dust would be an extra problem.
But surely the only significant capacitance or conductance between battery and chassis is in the motor. And surely the motor must be isolated from the battery during DC charging.
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Post by acmotor » Tue, 27 Aug 2013, 22:34

weber wrote:
coulomb wrote:I think it's because an EV has capacitive coupling to the (usually) metal chassis. A non-isolated HF switch mode power supply would have high frequency square waves between windings and chassis. You could conduct a lot of that away through the earth lead, but they prefer no current at all through the earth lead (except briefly in a fault condition to clear a breaker or RCD). Inductance in the earth lead would mean that there would still be some bite to the metal in many circumstances.

DC motors with their brush dust would be an extra problem.
But surely the only significant capacitance or conductance between battery and chassis is in the motor. And surely the motor must be isolated from the battery during DC charging.


Yes to motor isolation during DC charging, as per the iMiEV circuit at least. Wasn't there a charging system by tesla that used the motor as inductor ?

Either way, a non isolated HF SMPS would be a buck converter whose output, if being fed to a battery at least, would have had ripple deliberately removed. i.e. no switching artifacts (easy HF filtering).
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Post by weber » Tue, 27 Aug 2013, 22:57

acmotor wrote:Wasn't there a charging system by tesla that used the motor as inductor ?
Right. But that's for AC input. We're talking Chademo. That's why I wrote "isolated ... during DC charging".
Either way, ... would have had ripple deliberately removed. i.e. no switching artifacts (easy HF filtering).

Right. But I guess I'm in favour of hazardous EV voltages floating anyway. Is a HF transformer such a big deal?
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Post by Tritium_James » Tue, 27 Aug 2013, 23:24

The main reason for the transformer is probably that they're being paranoid. It's probably not necessary, and it definitely adds a lot of cost, bulk, and losses.

Yes, our charger (and any Chademo charger) monitors both the AC side for earth leakage, and runs an isolation monitor on the DC side as well. This has to be capable of being self-checking. There's also a check that applies full voltage to the cable before the car closes it's battery contactors, to check for cable isolation faults, shorts, etc.

The charger has to also match the requested current/voltage from the vehicle quite closely, or the sequence gets shut down. There's quite tight timing requirements on comms, ramp rates, response times, etc. It's fairly complex.

We passed Chademo certification (in Japan) in the fastest ever time, apparently. Still took over a week...

Don't get me started on the SAE Combo standard - the comms for that are a nightmare!

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Post by acmotor » Wed, 28 Aug 2013, 04:15

Lets be honest. In the scheme of things, CHAdeMO isn't complex, just good practice. Image

Well done on the lightning approval. Image After all, it isn't that complex. Image
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Post by acmotor » Wed, 28 Aug 2013, 05:54

weber wrote:
acmotor wrote:Wasn't there a charging system by tesla that used the motor as inductor ?
Right. But that's for AC input. We're talking Chademo. That's why I wrote "isolated ... during DC charging".....


Well there you go, and I thought it was common practice to charge a battery off 'DC' anyway. Image Sorry, I do get what you mean, CHAdeMO and all that. I was just going one step further since the emotor is isolated during AC charging as well (except the case cited) since it is still DC charging, just with the AC to DC conversion onboard. Image Ho Hum.
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Post by PlanB » Wed, 28 Aug 2013, 13:52

Bit of thread drift here TJ & MX twins, but how onerous & expensive is the Leaf servicing regime? I'm almost tempted to raid the Model S sinking fund to buy one except that the thought of new car ownership & having to take it back to the dealership for servicing to keep the warranty alive chills me to the core.
PS: I'm liking the impressive dimensions of your CHAdeMO beast TJ. With the ever increasing trend to miniaturisation it's been a long time since I've seen a piece of electronics that comes in at 2 metres tall. Reminds me of some 19" rackmount from my youth!

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Post by weber » Wed, 28 Aug 2013, 13:59

PlanB wrote: Bit of thread drift here TJ & MX twins, but how onerous & expensive is the Leaf servicing regime?
Just had first service. I have no idea what they did, except wash it, yay! But the first service is free. The next service is at 10,000 km and costs $90.
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Post by Tritium_James » Wed, 28 Aug 2013, 18:59

Yep, we paid $80+GST for the last service on ours. I think they check the wheels are still attached and give you the battery health printout!

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Post by PlanB » Sun, 01 Sep 2013, 15:50

OK I'm confused now. Went to a Nissan dealership & they have an Origin energy charging station about the size of a scuba tank plugged into what looked like a 3 phase outlet. They reckoned it recharges their demonstrator in 2 hours. That's too quick to be J1772 so it's got to be CHAdeMO right? I thought fast DC chargers were all 6' tall like TJs VeeFill? The Leaf is areal nice experience by the way, I'm very tempted.

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Post by Simon » Sun, 01 Sep 2013, 16:16

Would be a j1772 EVSE and clueless salesmen. Although if it was a 6.6kw leaf then 2hours would be all it would take to recharge from 50%..



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Post by PlanB » Sun, 01 Sep 2013, 16:31

I think you're right Simon. The module looks like a free standing level2 (7kw)from the Origin website to me. Thing is the car I drove is a 2013 demonstrator so it's limited to 3.3kw anyway. I had lots of questions about the Leaf's GPRS based telematics etc, but soon learned the sales person is not the one to ask.

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Post by bladecar » Sun, 01 Sep 2013, 19:32

When I have looked at a new Prius on a couple of occasions separated by a year or so, I found that that there seemed to be maybe just one salesman out of all of them who was THE MAN to talk to.   What that man really knew no longer worries me though they seemed ok.   The salesman we bought one off was very pleasant (and I must get on to the sales report thingie and tell Toyota so) and didn't profess to know a lot about it. It didn't matter as I was quite happy to find out for myself. I suppose the thing is that they are salesmen, not information providers, whatever we would like them to be.
I've seen somewhere that a salesman is really only a salesman if the customer bought a car only after at some point, having decided that they were definitely not going to buy a/the car.

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Post by Johny » Mon, 02 Sep 2013, 15:42

PlanB wrote:That's too quick to be J1772 so it's got to be CHAdeMO right? I thought fast DC chargers were all 6' tall like TJs VeeFill? The Leaf is areal nice experience by the way, I'm very tempted.
They take it out for a test drive then plug it in and it takes two hours to charge. That's a two hour charge - right.

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Post by Tritium_James » Mon, 02 Sep 2013, 16:17

Yep, it's limited by the 3.3kW charger in the car, so it's still 6-8 hours for a full charge. The salesmen are completely clueless about DC fast charging - the guy that sold ours didn't even know what the 2nd charging connector in the car was for...

PlanB, don't put too much hope on the telemetry. It's flaky and mostly useless. Most trips on our Leaf don't even show up on the website, and the ones that do are quite obviously the wrong distance. In fact I think you'd have to try pretty hard to make it any worse!

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Post by E-STATION » Mon, 02 Sep 2013, 16:20

PlanB wrote: OK I'm confused now. Went to a Nissan dealership & they have an Origin energy charging station about the size of a scuba tank plugged into what looked like a 3 phase outlet. They reckoned it recharges their demonstrator in 2 hours. That's too quick to be J1772 so it's got to be CHAdeMO right? I thought fast DC chargers were all 6' tall like TJs VeeFill? The Leaf is areal nice experience by the way, I'm very tempted.


The charging stations provided by the Nissan dealers are J1772 and deliver up to 32 amps. AFAIK there are no CHAdeMO charging stations installed in any Nissan dealership.

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Post by PlanB » Thu, 12 Sep 2013, 15:34

Good grief! Had a Leaf on charge here overnight, who's idea was it to insert a house brick in the cable 6" from the plug? Apart from a few blinkin' lights & the J1772 oscillator what other stuff could possibly be in there to make it so heavy? Recharged 100km in 5 hrs = 5 x 10 x 240 = 12kwh? So that makes the Leaf a 120wh/km drive?

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Post by Johny » Thu, 12 Sep 2013, 15:45

Ha. I agree with the brick comment. The best power economy we ever got was closer to 170Wh/km and that was on the car display - not the charging. As said earlier - it was during winter - but the days I drove it I turned Climate control off and it still wasn't anywhere near the iMiev (or Vogue).

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Post by g4qber » Thu, 12 Sep 2013, 15:46

Brian M's leaf drew 18A from e-station's 16A fbox
this box had a component replaced though.

the 15A Clipsal Powermate powermeter was having its overload LED lit.

will have to re-check this one day.

the genuine "emergency" Nissan EVSE was drawing <10A; which was good to know for Brian.
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Post by PlanB » Fri, 13 Sep 2013, 00:37

Yeah I'm a bit suspicious, 120Wh/km seems too good to be true but the EVSE kit that came with the car was definitely drawing only 10A and the range meter did go from 53km to 159km in 5 hrs

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Post by leighf » Fri, 13 Sep 2013, 01:00

I've been routinely getting (according to the dash) 160Wh/km in winter and was getting 140-150Wh/km in summer so 120Wh/km sounds suspicious to me as well.

The guess-o-meter is however notoriously optimistic so the indicated 100km of range added is unlikely to be achievable.

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Post by PlanB » Fri, 13 Sep 2013, 01:40

Interesting. I should have checked the mains current when we unplugged, maybe it tapered off throughout the 5hrs?

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Post by PlanB » Sat, 14 Sep 2013, 23:01

Better price than Origin energy, not sure the curled up cord is a good idea.

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