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Boomer23
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Re: Electrical charging - measured results, 120v vs. 240v

Fri Jan 14, 2011 10:45 pm

leafme wrote:Measured my LEAF tonight while charging to get a feel for the power input for 120v and 240v EVSE conditions.
Malcolm :geek:
Malcolm, thanks a lot for this great data. Your 240 V measurement seems to corroborate my TED's reading of 3.74 kW while charging Omkar's LEAF on my AV EVSE on Jan 1.
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DaveinOlyWA
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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 5:49 am

great info!! the advantage of 240 over 110 is much more than i had anticipated. i was looking for a closer to a slightly under 50%.

now, i will be using Killawatt for all my home charging so will have a good line on charging efficiency using 110 volts.

now, as i understand it, the faster the charge, the lower the efficiency due to greater heat generation?
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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 6:10 am

Nice! Thanks for doing that.
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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 8:40 am

garygid wrote:The wall clock is only helpful if the current usage is constant.

However, from graphs of the current, the LEAF takes a substantial "siesta" before the last "burst" of charging.

Thus, the constant-current assumption that you were using is substantially wrong, especially for short-duration charges like your 1.8 hour charge. Perhaps 0.4 hours were "siesta" (zero current), and another 0.4 hours with the current tapering off (perhaps averaging 75% of full current).

During the "siesta", the cells MIGHT be doing some voltage-equalizing.
That's an encouraging concept - but do you believe it holds true to that extent even for an 80% charge? If it is the case, and the described L2 charge took less than the estimate based on constant current, that would indicate L1 charging is vastly less efficient, because the 14.85 kWh L1 charge to 80% (and accompanying low m/kWh) was measured, not estimated. That L1 charge measured total was also pretty well in line with the max constant L1 current multiplied by the elapsed time (14.85 kWh/11.5 hours = 1290 watts), which points to minimal "siesta" time if any when going to 80%, at least at L1.
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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 8:43 am

DaveinOlyWA wrote:now, as i understand it, the faster the charge, the lower the efficiency due to greater heat generation?
In general yes, but the car's cells have very low internal resistance, and both L1 and L2 are very low rates of charge relative to the pack's capabilities, that I don't expect we'll see any pack heating with either. We should see a thermal difference between L1 and DC quick/L3 though.

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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 3:20 pm

When we see the actual charging graph for an 80% charge, we will know more.

It is quite possible that an 80% charge does not include the "equilization" period, and the top-up. But then, when would equilization ever get done?

I seem to remember some mention that some equilization gets done (at least started) each time you turn the car ON.
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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 5:03 pm

garygid wrote:When we see the actual charging graph for an 80% charge, we will know more.

It is quite possible that an 80% charge does not include the "equilization" period, and the top-up. But then, when would equilization ever get done?

I seem to remember some mention that some equilization gets done (at least started) each time you turn the car ON.
There shouldn't be any reason to balance cells at any time during a charge from 0-80%. The little bit of info in the service manual suggests higher cell voltages and those won't happen until we get into the 90-100% range unless we have some really out of whack cells. Maybe later as the cells age, but shouldn't be happening this early in the pack's life.

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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 5:12 pm

I was speaking of the case where one ALWAYS charges to 80% (and NEVER charges to 100%).
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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 9:51 pm

It will be interesting to see if the designers foresaw this possibility and programmed in a "forced 100%" charge every now and then (every few thousand miles?) to ensure cell balancing. Without some per-cell electronics (which I admit, may exist for all I know), I don't believe you'd be able to ever equalize the pack otherwise..

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Re: Electrical charging - measured results, 120v vs. 240v

Sat Jan 15, 2011 10:13 pm

Balancing is something that should be working all the time even at 80%. If not then overcharging of high cells would be nearly unavoidable if charging to 100% which is one reason why 100% charging can be problematic.
Something I thought about was setting charge to 80% then letting it sit a bit then charging to 100% but not sure if the times would work with 110 volt charging being so slow
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