What is the Charging efficiency for Leaf ?

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Well-known member
Apr 22, 2010
Seattle, WA
There have been some sporading discussion of the charging efficiency in various threads. I wanted to get your opinion in one thread.

I drove 32 miles yesterday from the dealer. Blink showed 13.58 kwh of charging at night - so it comes to 2.36 miles/kwh wall to wheels.

Assuming 80% charging efficiency, that would be about 2.95 mpkwh or some 71 miles range. If the efficiency is higher, say 90%, we are looking at just 63 miles of range (2.6 mpkwh). That looks a little low, given my freeway driving was limited to 55 to 60, even though the temperature was 30 deg and the climate control was consuming about 3 kw. I've seen a figure of 85% for charging (like Prof Bossel).
Does LiMn have lower charging efficiency than LiFePO4? Because I'd expect around 90% or better.
JRP3 said:
Does LiMn have lower charging efficiency than LiFePO4? Because I'd expect around 90% or better.
When I say charging efficiency, I'm talking about AC-DC conversion + battery charging i.e. wall to battery.
In a 3.3kW charging assuming AC-DC 97% efficiency, and low internal battery resistance around 0.005 Ohms the total efficiency could be around 95%.
In a quick charge 50kW (assuming constant power) it would be around 90%.
This is going to be hard to calculate without a true SOC meter showing Ah available in the pack. I suppose Turbo could use his laptop to read the value on the CAN to compare to his TED meter on the wall outlet. Phil probably has a way to read the SOC with his instrumentation, but for a regular user without this information it is just guessing.
I have to agree with JRP - my Chinese chargers are more efficient than that as well. Beware the ghosts of yesterday's lead and nickel. ;)

That's it - we need a MNL theme song to help us get our heads in the right place.

Change "pentiums" to "lithium"


It's all about the lithium, baby! :lol:
All we can determine with some certainty at this point is the total AC KWh from the wall into the car as measured with a Kill-A-Watt, TED, or similar, and the total miles driven as measured by the car's odometer.

If we want to calculate the charger/battery efficiency, we have to assume that the onboard DC kWh reading is correct. Reading the many posts, it seems to me that we haven't figured out how to get trustworthy DC kWh numbers from the car yet.

So I believe that we can calculate AC mpkWh fairly well, but not DC mpkWh, nor the charging/battery efficiency.
If we dig thru the service manuals, and then bribe Ingineer and/or Turbo2ltr with some sort of lubricant ;) we might find that we can either obtain a direct kWh reading, or get a very reasonable number using the car's state of charge info.

The car has a current sensor on the charger so we should have DC from charger to pack on the CAN buss. The car also has a current sensor from battery to inverter - that should be on the CAN buss as well. SoC is there as well - Turbo is working on that now.
As you may already know, I had a TOU meter fitted late Tuesday morning. It was fairly sunny that day, and we didn't need any grid power until late in the afternoon. The next morning, after charging the car, the meter showed that I had pulled 24kWh from the grid. So that's household for the night and charging from ~33% (4 SOC bars showing). Assume a worst case of 25% if you want.

This morning, without needing to charge the car last night, the meter showed that I had taken an additional 6kWh from the grid for household use since checking the meter late afternoon yesterday.

Since both days had similar usage other than the charging (maybe a hair more yesterday), I would have to assume that the car needed 18-19kWh to charge to 100% on Tuesday night, 20kWh at the very most.
Got another data point for you - checked the meter just before going to bed last night and it was at 85kWh. This morning, immediately after charging, I checked it again and it was at 106kWh. So that's 21kWh from 9pm last night to 6am this morning. Allow 2-3kWh for the house in those 9 hours and that is, once again, 18-19kWh to fill the car from ~66% depleted.
its going to be hard to correlate any real numbers when we have to thumbnail the usage on the house. i have a daily use meter that i can access online and it varies GREATLY. mostly because we have electric dryer and on clothes day, it skyrockets. now that i am charging my Leaf, i find that 120 volt charging has great advantages as far as monitoring what i put in and get out to the point where i am going to use public charging rarely for a while until i can get a good idea of the numbers i am seeing.

but if i take my MPK numbers from the car. divide it by miles driven, i get what is alleged to be power used my car in DC. if i divide that my my power from wall recorded by Kill a Watt which is supposed to be all but dead on, i get a ratio of around 70%
mwalsh said:
Oh, I see what you guys are looking for....DC figures. I can't be much help with that.

LOL!! oh ya, its easy to understand why u think its not an issue since you essentially charge for free.

i envy u in a way you could never understand
Well you should consider the AC -> Battery efficiency since that's all on-board, right? Not just the DC charger output -> battery efficiency. But hey, to each their own...

Here's what I'd do:

Step 1) Locate the DC output wiring for the charger. (Image borrowed from Ingineer and this thread)


Step 2) Gear up: Get yourself a clamp-on meter. Be prepared to drop $200+ for one that will measure DC current, though, as the vast majority will only do AC. If the meter doesn't have a set of leads and the ability to measure DC voltages (up to 500V minimum I'd say for the LEAF's pack) then you'll need a second meter for that too.

Do what you need to get the current meter around either of the DC leads coming out of the charger. Measure the current while charging - probably around 3-5 amps DC for Level 1. Measure the voltage across the two DC leads and multiply the two to get a power reading.

Use your Kill-a-watt to measure power at the wall socket. Trust the LEAF's dash output to measure power consumed (mi/kWh). Now you know, approximately, what's going in from the wall socket, what's coming out at the wheels, and a point between the charger and battery. With this you can get a rough idea of what's going on from Wall->Charger, Charger->Battery and Battery->Wheels.

Naturally the actual power varies during the charging cycle. Someone had a graph they got from TED which showed power as a function of time but there are so many graphs posted to this forum it's impossible to find :lol: - so serious bonus points for whipping up your own computerized DAQ to monitor DC power.