Is the Lizard really 25 KWH?

[tkdbrusco]

I found some interesting data on my pack after taking a reading last night. Let me know what you guys think of the below assumptions...

I got home last night with a low 18% charge. I know it was nearing the 17% switch since I'd been driving around for 1-2 miles with 18% on the dash.

So I took a reading at this low percentage because I hadn't done so before. I usually only took them at a higher SOC. Here's the reading.

50 GIDS
3.88 kwh
25.93% SOC
87.21% SOH
88.53 HX
57.78 Ahr
59 degrees
My car has 22,075 miles on it.

What I found strange about these numbers was the 25.93% SOC compared to the 18% on the dash reading. This wound indicate that the car is holding back about 7.8% at the bottom of the pack, and given that it only ever reads as high as 97.3% SOC when full, there's another 2.7% at the top. So we have roughly 10% of unused capacity in play here? This caught my attention because when I took a reading a few weeks ago with 41% charge reading on the dash, my app said 44.82% (only a 3.82% differential). Where did the extra 4% come from on last night's reading?

Furthermore, if you extrapolate the data out and realize that the most kWh we've ever seen in a new 2015 has been 22.6 kWh of usable capacity, and add back in the 10% of hidden capacity, you get a 25kwh pack (not 24!) Furthermore if I scale out the 50 Gids/3.88 kWh comparison, I'll find that 22.6 kWh is equal to exactly 292 Gids.

Does this prove that the pack really does have more than 24kwh? Is there actually 25kwh in there? Is the Lizard nothing more than a slightly bigger pack with 1 kWh of cells that are eaten away as the battery degrades? I suppose the only way to find out for sure is the drive the pack down to absolute zero (maybe I'll do this tonight?) and see what the completely dead pack shows for remaining capacity? If it is showing roughly 7% with 0 Gids remaining, then I think we've proven that the 24kwh pack is actually a 25kwh pack.

Or am I missing something here?

 

[edatoakrun]

...am I missing something here?

AVTA testing showed the range of capacities in 2012 and 2013 LEAFs:

http://avt.inel.gov/fsev.shtml

IIRC, average baseline static capacity for 2012s tested was ~23.4 kWh, and ~24.2 kWh for the 2013s.

I would expect newer "24 kWh" LEAF packs have probably continued to have greater average capacity since 2013, but I am concerned you are at risk of driving yourself mad if you continue to try to calculate battery capacity based on LBC readings...

 

[tkdbrusco]

Oh yes. I do drive myself mad with the analysis of the battery!

Here's a new one taken last night at 10% of charge remaining on the dash.

Reading on the App...

29 GIDS
2.25 KWH
17.93% SOC

Meaning that there's 7.9% hidden in the bottom, and another 2.7% hidden in the top, for a grand total of about 10.5% hidden capacity. Scale out these numbers based on my best ever reading of 292 GIDS and 22.6 KWH and you'll find that if you include this reserve capacity, the pack must be 25 Kwh total.

 

[DaveEV]

To confirm, do the following:

1. Drain to turtle, grab pack and cell-pair voltages and other data (gids, SOC, pack temp, etc).
2. Charge back up to 100% with an EVSE or circuit that can measure energy usage.

 

[minispeed]

I've linked to this before, take it for what it's worth.

This place sells used leaf cells and makes packs for DIY application. They have a lot of info on tests they did early on. The say that the max voltage of each cell is 8.4 regardless of year.

11/12 cells they say are 60 Ah
13/14 cells they say are 62 Ah
15 cells they say are 64 Ah

do the math with 48 modules and you get
11/12 = 24.192 kWh
13/14 = 24.998 kWh
15 = 25.804 kWh

http://hybridautocenter.com/HAC4/in...4&name=lithium-batteries-and-packs&Itemid=605

I don't know enough to say if their claims are accurate.

 

[tkdbrusco]

My calculations don't put it that high, but I think they are easily 25 kwh.

 

[tkdbrusco]

I've also noticed that the reserve capacity at the bottom differs with outside temp. Looking at some old readings from the summer when I was at 10% of remaining power, leaf spy said 15.2% on the app, but last week when I did the same test, it said about 19%? Would there be any login behind reserving more capacity on the bottom when temps are low? This could also explain the phenomenon of the 2015 packs having drops in max GIDS during the winter months and then picking back up in the summer.