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Kia e-Niro MY20 64 kWh - Gravity Blue
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Which manufacturer is advising charging to 100% regularly to ‘balance cells’?

And how does that square with the fact that you can’t charge a BEV pack to 100% anyway, Tesla excepted?

Ergo, the BMS can balance at less than 100%.
Yes it can, but it'll not balance when it's below its defined 100% SoC. The Kia Connect app even has an indicator on the status screen that indicates 'balancing'. The battery icon will blink or something like that. You can also check what's happening once 100% is reached. You'll see the charging voltage drop since at that moment the BMS starts balancing the cells and will try to bring the lower ones up to the voltage of the higher cells. This process may take a couple of minutes or an hour, depends on the state.

Another indicator that it does not balance throughout the charge is that once cells are un-balanced (check via an ODBC reader), they will remain unbalanced until you charge to 100%
 

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Kia e-Niro MY20 64 kWh - Gravity Blue
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That’s a conscious choice by Kia, which is fine, but just confirms my point that a BMS can balance individual cells at less than 100%.

I get that Kia call it 100% for ease of understanding by customers, when it’s actually 90% in reality.
Yes, but it will NOT do it while charging to lower percentages than the (virtual) 100%.

I also believe you're overly optimistic about the top buffer. It's a generally accepted fact that the e-Niro has a gross capacity of 67 kWh. So 100% SoC will be closer to 97% than 90%. Good thing is though that the NCM622 chemistry has a better resistance to high SoC than NCM811.
 
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