Battery Cell Voltages on FDRS

[louibluey]

Spent a few minutes looking around FDRS after today's TSBs were done. Came across BECM battery cell voltages. Here is a sample: (click on the pic for a larger image) (FE extended range, 4,468 miles) 98% SOC, not sure why it blew through my 80% charge limit last time, which almost always works. Two images, top of page, and scrolled down to bottom of same page.

 

[SnBGC]

Interesting how a cell with lower voltage reads with higher Ah capacity. Cells 31 and 69 comparatively. If I understood more about cell technology then I might be able to make some sense of that.
Cool stuff though.

 

[Mach-Lee]

Yes, this pack is doing very well. Only 8 mV for the cell balance delta (different between lowest and highest voltage). Imbalance should be less than 20-30 mV in a good pack. For comparison, GM specified replacement in their previous Bolt recall when the imbalance reached 80 mV.

You can also see your battery capacity and calculate your state of health. Based on each cell being 72 Ah, the extended range pack (4P) would be 288 Ah and the standard pack (3P) would be 216 Ah nominal. In this case the capacity is still at 100% health (288.34/288 = 100.1% SoH) which is impressive considering it has 4400 mi and is almost a year old. Might be good to make a note of the readings so you can track your battery degradation over time.

The display represents the pack module layout, left of screen is the front of the pack and the Tier 2 modules on the right are the second layer that form the bump under the back seat. You can also see the thermistor temperature readings. Note: not all cell modules have a thermistor, I believe the BECM only has 8 thermistor channels available so that's why.

You should also realize that the results may be different depending on the SoC; imbalance will be greater above 90% and below 30% SoC, and capacity may not fully update until you do a full charge. I always recommend keeping your battery between 20-90% for everyday use unless you need the extra range in order to maximize battery longevity. Readings may differ significantly from day to day, this is normal.

 

[Eric_C_Boston]

Looking at the Extended Battery display there appears to be a slight problem with the display when I compare it to the WSM.

The temperature of module 4 is likely for module 1. It appears the battery thermistors were originally laid out for 2 banks of 3 (A - F) in the BECM and then an additional input for each bank was added (G,H). It would be interesting to see the FDRS display on a Standard range battery.

C4816D
Pin Ch? Use
 2  A  ER03
 3  B  ER01 SR1
 4  C  ER05 SR3
 6  G  ER06 SR5
 7  Return
 9  D  ER07 SR7
10  E  ER08 SR6
11  F  ER11
13  H  ER12 SR9
14  Return

 

[louibluey]

Looking at the Extended Battery display there appears to be a slight problem with the display when I compare it to the WSM.

The temperature of module 4 is likely for module 1. It appears the battery thermistors were originally laid out for 2 banks of 3 (A - F) in the BECM and then an additional input for each bank was added (G,H). It would be interesting to see the FDRS display on a Standard range battery.

C4816D
Pin Ch? Use
2  A  ER03
3  B  ER01 SR1
4  C  ER05 SR3
6  G  ER06 SR5
7  Return
9  D  ER07 SR7
10  E  ER08 SR6
11  F  ER11
13  H  ER12 SR9
14  Return

Eric, Could you explain the code, and how you read it? Thanks!

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