> >>>
>>> DO not ask whether I am trying evil things.
>>> I just wanna return a rechargeable battery
>>> back to safe state.
>>
>> If it is in a safe state it is no longer rechargeable.
>
> You mean when rechargeable battery is fully
> discharged, it really become a DRY cell? :)
>
No. It becomes sufficiently chemically altered that it will no longer accept charge. Like setting off an atomic bomb is how you make it safe.