when your charging your putting in what was taking out.
similar to a bottle of pop if you buy 500ml drink 100ml you can only put 100ml back in then it's full any more will over fill. Try and force it in will cause more pressure inside and will need to vent to release that pressure.
To be that high in volts they have been overcharged a few times.
The worst about anyone elses batteries you have no clue how they was treated and will end up costing more than just buying a new in packet pack.
Was you the one thinking about a power supply. i have just modded the ps3 unit. 23.5A 12V delivered to door then modded for less than £10