Why does it take longer for the last 10-20% of a (EV) battery to charge compared to the bottom ranges?
In: Engineering
It actually has nothing to do with over charging as the other answers state and everything to do with heat.
Another clarification worth nothing is that not only is the last 10-20% slow to charge but the first 10-20%.
Due to internal resistance batteries heat up when charged and discharged. Taking the battery above a certain temperature will damage the battery permanently. The internal resistance is higher when the battery is nearly flat and nearly full. The charger thus puts in less power for these periods to stop the battery over heating.
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