Battery Buffers

[JTM]

I assume that only making 18.8kWh of power available from the i3's 21.6kWh battery, is to provide a buffer in prevention total charge depletion (bricking) but does it also serve the function of reducing an overly high full charge in order to extend battery life?


Still learning so much about these cars!

JTM

 

[Jeffj]

There is a lot more to the equation than just "18.8 usable out of 22". The extra capacity helps with keeping discharge rates high as the battery depletes (think of a tape recorder slowing down as the batteries run out - not a desirable characteristic in an automotive battery), helps balance out the charging load, accounts for high and low temperature performance, etc. Most electric's have extra capacity to make up for these characteristics. I think the Volt has something like a 30% buffer in its batteries for just these reasons. I think BMW would have been better served by just stating 18.8 or 19 kWh as the capacity, as the term "usable" capacity tends to create too many questions.

 

[jadnashuanh]

There is a substantial buffer maintained at both the top and bottom of use of the battery to maximize its service life.