jgc
Posts: 3
Joined: Wed Feb 20, 2019 10:41 am
Delivery Date: 10 Jan 2019

What's the charging efficiency?

Wed Feb 20, 2019 11:40 am

I've looked around this board, and elsewhere, but can't seem to find an answer to what I hope is a simple question.
My LEAF is 40kWh ... but I don't know how much electricity it takes to charge it up to 40kWh. Is a bit more (say 45kWh) or a lot more (60kWh) or even more? I guess this will be different between different PVSE systems in different countries; ideally I'd want to know it for the UK for typical home charging pods (6kW in my case).

I'm interested to know this so I can more precisely understand what my 'fuel' costs are.

LeftieBiker
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Re: What's the charging efficiency?

Wed Feb 20, 2019 2:46 pm

You need to post your cost per KWH. Then, we can multiply that by about 37, if you like. ;-)
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

WetEV
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Location: Near Seattle, WA

Re: What's the charging efficiency?

Wed Feb 20, 2019 3:09 pm

jgc wrote:I've looked around this board, and elsewhere, but can't seem to find an answer to what I hope is a simple question.
My LEAF is 40kWh ... but I don't know how much electricity it takes to charge it up to 40kWh. Is a bit more (say 45kWh) or a lot more (60kWh) or even more? I guess this will be different between different PVSE systems in different countries; ideally I'd want to know it for the UK for typical home charging pods (6kW in my case).

I'm interested to know this so I can more precisely understand what my 'fuel' costs are.


Efficiency of charging is near to 85 percent. So if the battery was actually 40kWh, and it was empty, it would take about 47kWh to charge to full. This isn't realistic for several reasons. The battery is actually somewhat smaller than 40kWh when new. The capacity of the battery changes slightly with temperature. And charging from empty to full should be a very rare event.

Best practice would be to keep the battery from being much below 40% charge, and charging to 100% only when needed, and leaving within an hour or two.
WetEV
#49
Most everything around here is wet during the rainy season. And the rainy season is long.
2012 Leaf SL Red (Totaled)
2014 Leaf SL Red

SageBrush
Posts: 4218
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

Re: What's the charging efficiency?

Wed Feb 20, 2019 4:19 pm

90% is pretty close
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

jgc
Posts: 3
Joined: Wed Feb 20, 2019 10:41 am
Delivery Date: 10 Jan 2019

Re: What's the charging efficiency?

Wed Feb 20, 2019 5:47 pm

Many thanks, @WetEV and @SageBrush. That's good enough for me to go with. I don't have a clean way of telling what my electricity usage is just for the car charging, so want to estimate it from what the car says it's taking in.

SageBrush
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Location: Colorado

Re: What's the charging efficiency?

Wed Feb 20, 2019 7:30 pm

https://iaspub.epa.gov/otaqpub/display_ ... 416&flag=1
Page #6

The EPA metered the amount to charge the car from a SoC of zero to 100% using an L2 charger (~ the same as OP) at 44.8 kWh. Works out to 11% charging losses presuming 40 kWh maximum available

At the bottom of the same page Nissan reported 209 Wh/mile from the battery and 239 Wh/mile from the meter:
1 - (209/239) = 12% charging losses.
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

8leaf
Posts: 5
Joined: Thu Nov 08, 2018 11:32 am
Delivery Date: 28 Sep 2018
Leaf Number: 310910

Re: What's the charging efficiency?

Tue Feb 26, 2019 2:23 pm

Or you can calculate that using what's available thru the instruments of the car.
What I did is write down the percentage and miles available before I start trickle charge overnight, which is 1,4 kWh as reported by the car on 120V 15A standard plug using the stock evse on 2018.
Assuming the battery is 40kWh at 100% you can figure out how much it went in at the end of your charging session. For me this is 10 hours(10pm - 8am) , which translates to roughly 30% gain in available charge/ range.
40kWh*0.3 =12 kWh(~45 miles) added in 10 hours and 10*1.4kWh = 14kWh. So used 14kWh to gain 12kWh in the battery, which translates to 85,71 % efficiency.
You might get lower efficiency if you charge on L2 (~7kWh) or QC due to more heat build up in the battery.
Will have to check this once I install L2 at home or record some of the L2 or QC public charging sessions to see what the efficiency would be.
The problem would be the QC since it's not a constant kWh rate and it fluctuates or rather tapers of to prevent overheating of the battery.


If you care about estimated cost of ownership you can download this app:
https://mygreencar.com/

not perfect but I can track my speed/distance and travel times and see how much it would cost me between my virtual cars.

They're still in beta and not sure if available at your Region.

tomcon
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Joined: Mon Jan 07, 2019 1:08 am
Delivery Date: 30 Oct 2018
Location: Seattle, WA

Re: What's the charging efficiency?

Tue May 28, 2019 10:43 pm

I am only getting about 76% efficiency at L1 the way i calculate it.

I have a KwH meter on the plug, so i measure the KwH going out of the plug and into the car that way.

I reset the car's meter and the plug meter at the same time.

Here i'll illustrate my calculation. For 153 miles driven (across multiple charges), the meter reported 61.2 KwH. In the meanwhile the car reported 3.3mi/KwH corresponding to the same 153 miles. So, at 3.3 mi/KwH, simply dividing, the 153 miles = 46.4 KwH. I calculate that the car reported 24% less KwH than the plug [my calc: (61.2-46.4)/61.2 = 24%]. Those numbers are typical for other repeated measurements I've done (tracked for several months), always in the range 23%-25% less reported by car compared to plug.

I keep seeing people report much higher numbers, not sure why mine seem like so much more is lost, unless L1 is that much less efficient than L2. I was using climate control during this time (winter, but in Seattle so not too cold). I assume the 3.3 mi/KwH the car reported included the draw from climate control.

WetEV
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Re: What's the charging efficiency?

Wed May 29, 2019 4:12 am

tomcon wrote:I am only getting about 76% efficiency at L1 the way i calculate it.

I keep seeing people report much higher numbers, not sure why mine seem like so much more is lost, unless L1 is that much less efficient than L2. I was using climate control during this time (winter, but in Seattle so not too cold). I assume the 3.3 mi/KwH the car reported included the draw from climate control.


L2 efficiency is much higher than L1.
WetEV
#49
Most everything around here is wet during the rainy season. And the rainy season is long.
2012 Leaf SL Red (Totaled)
2014 Leaf SL Red

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Nubo
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Re: What's the charging efficiency?

Wed May 29, 2019 12:22 pm

8leaf wrote:... I start trickle charge overnight, which is 1,4 kWh as reported by the car on 120V 15A standard plug using the stock evse on 2018. ... You might get lower efficiency if you charge on L2 ....


Nope, L2 is more efficient because the electricity required to run the water pump and other systems is a smaller percentage of incoming power, and they run for a lot less time than they would with L1 charging.
I noticed you're still working with polymers.

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