math help - chargepoint/dcqc/240 volt/GOM

[ksnogas2112]

Ok, can you guys give me a little math help?

2012 Leaf - original owner
1 capacity bar down and the obd/odb??? device I got didn't work with my phone...
Yesterday, I plugged into the DCQC (Chargepoint) and it said I was at 29% charge. However, the car said I was 'low battery' with 1 range bar left (plus the hidden 1 bar). I plugged into the DCQC and charged to ~35% which was 3 bars and got home with low battery just popping up.

Fast forward to today. Plugged into the 240 volt Chargepoint device at the office. Current (pardon pun) state is 'active charging' but it's drawing 0 Kw. I didn't set the 80% override to 100% so it should be at 80%.

The pack holds 24kWh right?

Only 22 are available to protect the top and the bottom?

20% degradation of 22 is 17 kWh right?

Charging to 80% of 17 = 13.6

Consumed 12.2 so the remaining 1kWh on the math should have been what was left in the car when I plugged it in right?

So how was the DCQC coming up with 29% when it looks like there was only around 1kWh in the pack with the low battery warning just starting?

Or did I miss something (entirely possible- history major not math major)?

Tom

 

[DaveinOlyWA]

I think you are simply wanting a super smart charging station and that is not what you will get. for one thing; a brand new pack does not accurately report SOC to the station or the station does not accurately access the SOC or something. In the grand scheme of things the real thing we can take from this is the charger has a varying level of inaccuracy.

Now all chargers are different and even the same charger at different times is different...

My real question to you is what was your role in making your area the soon to be "most EV friendly" city in America?


on your question; you are mixing two different things. if using a "cup with sand" analogy for degrading battery packs, you have a 20 oz cup that holds 20 oz when new but then you "degrade" it by adding a volume of sand equal to 10 oz of water. You now have 50% degradation or maximum of 10 oz of water. so if at 50% SOC would you have a 3rd party observer see 5 oz of water or a level "conforming" to 15 oz? (10 of sand, 5 of water)

 

[TomT]

A brand new pack has about 21.5 Kwh of usable capacity...

The pack holds 24kWh right?

 

[desiv]

So how was the DCQC coming up with 29% when it looks like there was only around 1kWh in the pack with the low battery warning just starting?

DCQCers are notoriously bad at battery percentage, at least with the older Leafs.
I know on my 2012, it's high until somewhere in the 30% range, then it gets behind on the percentage.
By the time it thinks I'm "done", I'm usually somewhere about 83%..
(I don't usually leave the car for a "full" DCQC, but it's happened a few times so I know how off it is..)

desiv