value of my 2014 Leaf

[WetEV]

Good test, and good result. An L2 EVSE has about 12% losses during charging so your test implies ~ 18.6 kWh usable, very close to losing the 12th capacity bar. Everybody should evaluate their cars the way you have done.

If the battery wasn't cold. I'd bet it was, this time of year.

I'd only driven about 2 miles to charger. Yes battery probably cold. So if cold, what would be different? Not a good test? Not a good result? No 12% loss during charging?

TLDR: You will have more battery capacity than 18.6kWh at a battery temperature of 25C.

Li ion batteries generally have a peak capacity at a specific temperature, and lower capacities at both higher and lower temperatures. I don't have enough data to say exactly how much lower. Start here:

https://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures

Warning, different chemistries have different properties over temperature. Getting good numbers on what the LEAF cell capacity vs temperature isn't easy. The graph below is for a "Commercial cylindrical lithium-ion cells rated 700 mAh, 3.7 V". The LEAF's battery is different. The "Leaf Range Chart" gives "Subtract 1% from range for each 4F/2C below 70F/20C", and I'm fairly certain that the actual loss of capacity with lower temperatures isn't as large as that based on my recharge data. I'm also fairly sure that the LEAF drops off faster than the graph below.

So if your battery was at 0C, the graph below would suggest your temporary loss due to lower temperatures as ~4%, if the cell chemistry was identical to the LEAFs.

My advice is to do this test at as close to 25C battery temperature as reasonable, and be consistent at the temperature between tests. Use LeafSpy to get battery temperatures, the TBs are too coarse to be useful.

Source:
doi: 10.1149/2.0591803jes
J. Electrochem. Soc. 2018 volume 165, issue 3, A674-A679

 

[rawlins02]

So if your battery was at 0C, the graph below would suggest your temporary loss due to lower temperatures as ~4%, if the cell chemistry was identical to the LEAFs.

My advice is to do this test at as close to 25C battery temperature as reasonable, and be consistent at the temperature between tests. Use LeafSpy to get battery temperatures, the TBs are too coarse to be useful.

Good info. Appreciate the help. For now I'll assume battery is capable of storing closer to 20 kWh. I have LeafSpy on phone, but do not have the dongle. Yes would like to do more tests at 25C. Hope to have car evaluated in near future at the CarMax store in Westborough as @RonDawg suggested earlier.