rkshack
Posts: 36
Joined: Tue May 29, 2012 5:01 pm
Delivery Date: 28 May 2012

charging efficiency

Sat Jun 02, 2012 7:36 am

I am not sure the best way to ask this question. If I fully charge my leaf from 0 to 100% how much electricity does it take to do that. I know the battery holds 24kwh. How much of my house hold electricity does it take to fill that 24kwh. Is there some loss somewhere in the system that makes it use 25kwh of my electricity. I can't imagine that it is 100% efficicient. Also is there a difference in that efficiency with a home charging station and the trickle charger?

rkshack

adspguy
Posts: 94
Joined: Tue Apr 10, 2012 1:12 pm
Delivery Date: 23 Apr 2012
Leaf Number: 018978
Location: Newton, MA

Re: charging efficiency

Sat Jun 02, 2012 7:46 am

From what I've read there is a flat 300w loss during charging. Using an L2 evse makes it charge faster so the 300w loss is for a shorter time, therefore the efficiency is better. I was using the included l1 evse but then had Phil at evseupgrade upgrade it to L2 rev 2 so I get the fastest L2 charging and the lowest cost L2. I highly recommend that approach, especially if like me, you can't score one of the free L2.

rkshack
Posts: 36
Joined: Tue May 29, 2012 5:01 pm
Delivery Date: 28 May 2012

Re: charging efficiency

Sat Jun 02, 2012 8:00 am

adspguy wrote:From what I've read there is a flat 300w loss during charging. Using an L2 evse makes it charge faster so the 300w loss is for a shorter time, therefore the efficiency is better. I was using the included l1 evse but then had Phil at evseupgrade upgrade it to L2 rev 2 so I get the fastest L2 charging and the lowest cost L2. I highly recommend that approach, especially if like me, you can't score one of the free L2.

Is the 300w for a full charge. So if I do a half charger from 12-24kw is the waste 150w. So if am doing my calculation for expense I should add .3 to the kwh that I am figuring. For example I pay $.086 per kwh from my power company. So If I can calculate 24.3 x .086 to give me my cost in dollars.

rkshack

adspguy
Posts: 94
Joined: Tue Apr 10, 2012 1:12 pm
Delivery Date: 23 Apr 2012
Leaf Number: 018978
Location: Newton, MA

Re: charging efficiency

Sat Jun 02, 2012 10:31 am

No it is 300w for the entire charging time. So, so say it takes you 12hours to charge using L1, with that you would be losing an extra 300w*12hours=3.6kwh. If you used an L2 for 5.25 hours instead, you would only lose 300w*5.25hours=1.575kwh. So you save a couple of kwh for about the same amount of battery charge.

Herm
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Location: Timbuktu, Mali

Re: charging efficiency

Sat Jun 02, 2012 11:49 am

Its 300w per hour

So it it takes 6 hours for a full charge then you used 300w x 6h or 1800 wh, or 1.8kWh.. since the average rate is $0.12 per kWh then that works out to 22 cents

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TonyWilliams
Posts: 10091
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Location: San Diego
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Re: charging efficiency

Sat Jun 02, 2012 11:52 am

73% at 120 volts
84% at 240 volts
90%+ on DC

Chieftan68
Posts: 28
Joined: Thu May 24, 2012 3:36 pm
Delivery Date: 18 May 2012
Leaf Number: 271
Location: San Diego County

Re: charging efficiency

Sat Jun 02, 2012 11:59 am

A lot has been made about the efficiency of the LV1 vs. LV2 charging :o . If you are making a decision based on cost savings between these two (that is, the recapture of the "wasted" kwh because of the longer recharge time of LV1) and not on the speed of the charging cycle (LV2 faster), you are wasting your time. :shock:

Using the provided example, you could recapture approximately 740 kwh/yr using the LV2 over the LV1. Even at my outrageous 14.4 cents per kwh, that's a yearly savings of about $107. If I could install a LV2 charger for about $1,200 (EVSE plus installation), the payback on that installation is 11 years :? . A lot more if the price of the EVSE LV2 charging station plus installation is greater than $1,200. :o Not a very good investment. :oops:

The above, of course, is based on stable electricity costs (maybe) and the EVSE LV2 charger staying the same price (not likely). Conjigure with those two inputs and the payback period may be a bit shorter if the charger comes down in price and electricity rates rise significantly.

In my particular case (based on yearly estimated driving), the payback period is 25 years. So, unless you need the benefit of a fast charge vs. a slow charge, there is no need to use an LV2 IF what you are after is significant efficiency cost savings between the two systems.

I only use an LV1 and do just fine.
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rkshack
Posts: 36
Joined: Tue May 29, 2012 5:01 pm
Delivery Date: 28 May 2012

Re: charging efficiency

Sat Jun 02, 2012 12:37 pm

TonyWilliams wrote:73% at 120 volts
84% at 240 volts
90%+ on DC

What are these percents?
rkshack

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Boomer23
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Delivery Date: 30 Mar 2011
Location: Orange County, CA

Re: charging efficiency

Sat Jun 02, 2012 12:47 pm

First off, you are not charging from zero to 24 kWh. Nissan has limited user access to only a percentage of the full pack capacity. Most of us accept the estimate that user available capacity is 21 to 21.5 kWh.

Owners who have charged at 240 Volts to "full" 100% charge from "turtle" (which is as empty as the car will allow you to get) in new cars with full battery capacity have reported using about 25 kWh from the power panel, as I recall. I think that I used 26.2 kWh, but my reading was considered an outlier.
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dgpcolorado
Posts: 3124
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Location: The Western Slope, Colorado

Re: charging efficiency

Sat Jun 02, 2012 1:24 pm

rkshack wrote:
TonyWilliams wrote:73% at 120 volts
84% at 240 volts
90%+ on DC
What are these percents?
rkshack
Those are the approximate efficiencies of charging the current LEAF at those voltages. As explained by others above, the 300 Watt "overhead" for charging is reduced with faster charging speeds.

I charge at 240 Volts, 16 Amps and get about 84-85% efficiency. This is calculated by comparing the power I use "at the wall" per mile with the power used per mile as reported by the car. In May my numbers were 4.36 miles/kWh at the wall and 5.1 miles/kWh in power use reported on the dash of the car.
4.36/5.1 = 85%
The missing 15% is the loss of the charging process.
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