Does 90-100% hold more kWh?

[devmach-e]

Agree, but that last 1% can take an hour.

Not entirely sure about that...

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[Mach-Lee]

At 99%, the battery charger switches from constant current to absorption mode charging. This means the pack voltage is held constant (about 390V) and the charger waits for the battery cells to soak up as much energy as they can. As this progresses, the amperage used gradually drops. When the cells are not taking any more amperage at 390V, then charging stops and it switches to 100% SoC.

The time it takes for the cells to taper at full voltage is dependent on the cell kinetics and temperature. If you have a warm battery, it will happen faster. Cold battery will take longer. It can also be affected by how out of balance the pack is. Charging may have to slow to wait for some cells to balance out before it can get all of them up to 4.15V.

If you haven’t charged to 100% recently, the BMS and balancing may be off such that it takes a much longer time to go from 99% to 100% (several hours) than if you just did it yesterday. If your BMS is off by 5%, then you will have to wait for that extra 5% to be put in between 99% and 100%.

The energy required to go from 99% to 100% is not constant because of the variance in accumulated BMS errors.

 

[devmach-e]

At 99%, the battery charger switches from constant current to absorption mode charging. This means the pack voltage is held constant (about 390V) and the charger waits for the battery cells to soak up as much energy as they can. As this progresses, the amperage used gradually drops. When the cells are not taking any more amperage at 390V, then charging stops and it switches to 100% SoC.

The time it takes for the cells to taper at full voltage is dependent on the cell kinetics and temperature. If you have a warm battery, it will happen faster. Cold battery will take longer. It can also be affected by how out of balance the pack is. Charging may have to slow to wait for some cells to balance out before it can get all of them up to 4.15V.

If you haven’t charged to 100% recently, the BMS and balancing may be off such that it takes a much longer time to go from 99% to 100% (several hours) than if you just did it yesterday. If your BMS is off by 5%, then you will have to wait for that extra 5% to be put in between 99% and 100%.

The energy required to go from 99% to 100% is not constant because of the variance in accumulated BMS errors.

Thanks for the clarification.

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