



I don't see any way that the concrete floor could do anything to the
battery.

However, you would have been better off leaving them outside. Keeping
them cold would have been better for them than bringing them inside.
A warm battery will self-discharge faster than a cold one.

When you are storing a battery it's a good idea to charge it once a month.
Letting a battery go completely dead is bad for it (I suspect this is
what caused your problems).

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