Battery Recall for cars with E400 high-voltage battery.

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68% is the BMS SoC which tracks how much usable capacity your battery pack has remaining. Display SoC will always show 100% at full charge as it scale the BMS SoC. For example, at ~34% BMS SoC, your Display SoC will show 50%, etc. It looks like your battery pack is failing fast if it dropped from 74% not that long ago - it won't be long before it's in the shop again for a battery replacement.
If the BMS SOC shown by Car Scanner shows how much of the original capacity is remaining, it seems to me to be identical to the SOH. If I'm wrong I'd like to know why.
 
You are close IanL but BMS SoC and SoH differ in three ways:

1. They will only be similar at 100% display SoC. As you use energy, SoH will stay the same while BMS SoC will decrease based on lowest cell voltage.
2. BMS SoC will be lower than 100% in most cars with top buffer. Eg if BMS artificially limits cells to 4.15v instead of 4.2v, BMS SoC may top out at 96% (100% - 0.05v/1.2v). SoH scales to 100% including the top buffer or in my 2018 case, it scaled to 110% when the car was new - it dependent on how each car manufacturer programs it. SoH changes as the cells degrade (see #3 below).
3. BMS SoC shows number based on lowest cell voltage. SoH is determined over the long term when you cycle the battery semi-fully depleting and recharging the battery. It's based on actual energy input and output measured through the shunt throughout the voltage range of the cells. Take lead acid battery capacity test as an example - at 100%, it may measure healthy at resting voltage but only have half the amp hours capacity when you try to actually use the battery - that's what SoH measure.
 
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andrew1joe : your theory does not match reality. Try reading through some of the longer threads on this forum for example the soulspy thread and then explain data such as this. see -Soul Spy?

Here are my numbers at 100% charged
battery.SOC_precise_pt 63.082
battery.SOC_pct 95
battery.SOC_display_pct
battery.available_charge_power_kW 69.69
battery.available_disharge_power_kW 90
battery.max_cell_detoriation_pct 36
battery.min_cell_detoriation_pct 22.1
 
JejuSoul, sorry I'm not as familiar with SoulSpy. For the example you posted above, do you have the mapping to PIDs and the equations used? Also does "SOC_precise_pt" map to BMS SoC and "SOC_pct" map to Display SoC or is that "SOC_display_pct" which is empty?
 
The author of SoulSpy told me he did not know what the parameters SOC_precise_pct and SOC_pct were, and he assigned the names by guesswork. From recent discussion (see post #214) it appears that SOC_pct is BMS SoC, SOC_display_pct is what the dash says, and SOC_precise_pct is unknown.

My current data is:
SOC_display_pct 81.5 (the dash shows 81)
SOC_pct 77.5
SOC_precise_pct 90.824219
battery.available_charge_power_kW 70.18
battery.available_discharge_power_kW 90
battery.max_cell_detoriation_pct not shown on 2018 model readout
battery.min_cell_detoriation_pct not shown on 2018 model readout

All cells show 3.9V
battery_max_cell_SOH_pct 0
battery_min_cell_SOH_pct 100


Mine is a 2018 model, so SoulSpy reads the SOH from the BMS and shows SOH 100%. My own computation from records of mileage, m/kWh and displayed SoC before and after charging suggests it is about 101 to 102%. ( I assume the BMS does not provide values in excess of 100%).
 
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Thanks Ian.

On the 2018 SoulSpy has changed the names
battery.max_cell_detoriation_pct to battery_max_cell_SOH_pct
battery.min_cell_detoriation_pct to battery_min_cell_SOH_pct

These are the same PIDs as the earlier model but have a different meaning.
Before they used to show the deterioration from usable capacity plus early-years buffer. The safety buffer is never lost and never shown by the BMS.
SOH is measured against usable capacity which enabled a calculation to be made.
100% of usable capacity + 10% of early-years buffer = 110%
It's a bit silly to use percentages greater than 100% but it does help accurately plot a graph to estimate when you'd reach 70%

The 2018 PIDs never showed this. Nor do the PIDs of any 27kWh car that has had a replacement battery with E400 cells with an updated BMS. I have no idea what the new values actually show.
 
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