Overcharging batteries to see what happens is not charging them more than 100% of their capacity.
When they are fully charged, no more energy can be stored.
It is like filling a gas can over it’s capacity. Sure you can keep pouring gas in the inlet, but it just escapes and makes a potential explosion.
All the energy is used up making explosive gasses.
They may find out what happens, but in the end they can’t get any more energy out than 100% of capacity.
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