WetEV wrote: ↑
Thu Jul 22, 2021 6:38 am
Drive the car until the battery is down to about 10%.
Plug into a charging station that records kWh delivered. Charge to 100%
The battery holds about the number of kWh delivered by the charging station.
There are a bunch of small effects that should be mentioned. Charging efficiency isn't exactly 90%, battery temperature should be at about 20C or 68F, metered kWh is likely off by a percent or two and I'm sure that there are more. But for a simple test, I don't think that this can be topped.
I also think that this is a good approach. To clarify though, ~ 0.9*the kWh metered goes into the battery.
There is however a more convenient approach that comes close in accuracy: A home EVSE is going to have a pretty constant charge until 90% SoC. So plug in at a low SoC, charge up to ~ 90% and calculate. A check after an hour of charging should give a pretty good idea when 90% SoC will be reached. It does not have to be exact.
A 30 Amp EVSE at 240v is used
Start at e.g 12% SoC
Charge 3 hours to reach 91% SoC
6 kWh per hour for 3 hours reached the battery so 18 kWh = 79% charge, and a full charge would be 18/0.79 = 22.78 kWh
It bears mention that both of these methods, in addition to the capacity bars meter, are not including any usable reserve. For that you need LeafSpy.