theaveng
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Why's 120 volt charge time so long?

Wed Oct 03, 2012 9:47 am

7 hours for 240V and 20 hours for 120V. I thought it would be exactly half for the lower voltage?
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ebill3
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 9:58 am

theaveng wrote:7 hours for 240V and 20 hours for 120V. I thought it would be exactly half for the lower voltage?
Looks like you thought wrong. :o
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davewill
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 10:02 am

The 120v charging is limited to 12amps (1.44kW). 240v charging is done at 16a (3.84kW). That comes to 2.67 times slower, plus 120v charging is less efficient...there's a fixed overhead for the cooling system that brings the practical difference close to 3 times slower.
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RegGuheert
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 10:05 am

theaveng wrote:7 hours for 240V and 20 hours for 120V. I thought it would be exactly half for the lower voltage?
You are correct about the voltage ratio, but there are two reasons for this apparent discrepancy:

1). The currents are also different. The National Electrical Code requires continuous loads to not draw more than 80% of the rated current of the plug, the 120VAC current is limited to 12A. The 240VAC setting limits the current to 16A, which is compatible with wiring gauge down to 12 AWG.
2). There is a parasitic load of about 300W that runs during charging. These pumps draw the same power regardless whether the charging is done with 120VAC or 240VAC. This power takes a larger fraction of the available power away from charging when using 120VAC, This further slowing charging. Interestingly, this causes 240VAC charging to be more efficient.

Because of these two issues, 120VAC charging tends to take about three times as long as 240VAC charging.
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gaswalla
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 12:13 pm

davewill wrote:The 120v charging is limited to 12amps (1.44kW). 240v charging is done at 16a (3.84kW). That comes to 2.67 times slower, plus 120v charging is less efficient...there's a fixed overhead for the cooling system that brings the practical difference close to 3 times slower.
there's a cooling system?

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davewill
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 12:17 pm

gaswalla wrote:there's a cooling system?
For the charger, motor and inverter, not the batteries.
Last edited by davewill on Wed Oct 03, 2012 12:30 pm, edited 1 time in total.
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derkraut
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 12:21 pm

RegGuheert wrote:
theaveng wrote:7 hours for 240V and 20 hours for 120V. I thought it would be exactly half for the lower voltage?
You are correct about the voltage ratio, but there are two reasons for this apparent discrepancy:

1). The currents are also different. The National Electrical Code requires continuous loads to not draw more than 80% of the rated current of the plug, the 120VAC current is limited to 12A. The 240VAC setting limits the current to 16A, which is compatible with wiring gauge down to 12 AWG.
2). There is a parasitic load of about 300W that runs during charging. These pumps draw the same power regardless whether the charging is done with 120VAC or 240VAC. This power takes a larger fraction of the available power away from charging when using 120VAC, This further slowing charging. Interestingly, this causes 240VAC charging to be more efficient.

Because of these two issues, 120VAC charging tends to take about three times as long as 240VAC charging.
Hey RegGuheert---I've gotta hand it to you; your post here is the first one that I can actually fully comprehend. I'm "electrically challenged" you see. YOU DA MAN! :mrgreen:
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RegGuheert
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 12:27 pm

derkraut wrote:Hey RegGuheert---I've gotta hand it to you; your post here is the first one that I can actually fully comprehend. I'm "electrically challenged" you see. YOU DA MAN! :mrgreen:
I'm glad it was useful for someone. After I composed it I saw that Dave had said the same thing in about one-third as many words, but I posted anyway in case someone cared about the additional details.

I guess Dave's reply was L2 while mine was L1! :lol:
RegGuheert
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10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
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gaswalla
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 12:31 pm

davewill wrote:
gaswalla wrote:there's a cooling system?
For the charger, motor and inverter, not the batteries.
that's a shame..

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RegGuheert
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Re: Why's 120 volt charge time so long?

Wed Oct 03, 2012 12:34 pm

gaswalla wrote:
davewill wrote:
gaswalla wrote:there's a cooling system?
For the charger, motor and inverter, not the batteries.
that's a shame..
Please note that the LEAF uses a more traditional automotive cooling system which is only capable of moving the temperature closer to ambient. It does NOT have a refrigeration system in the loop like the Volt so it would not very useful for cooling the batteries.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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