That would depend on the size of the battery, you want the amps of the charger to be reasonably proportional to the capacity of the battery.
6volts 2amps for 6 volt battery, and 12 volts 6amps for a 12 volt battery. Don't charge a 6 volt battery on the 12 volt setting or it will explode!!!!!!!!! you're ok going the other way though.
If your load runs on 6 volts, you cannot replace it with a 12 volt battery. You will be exceeding the voltage rating of your load and will start a fire.If you want more amps (capacity) then you can wire more 6 volt batteries in parallel with the first.
If it's a car/motorcycle battery you will be welding! If it's a small electronics battery nothing. Volts are not really the issue here, but amps are. And yes some old cars did or do have 6 volt batteries if not converted...
The formula you are looking for is W = I x E.
No, it will overcharge the 6 volt battery.
A 6 volt wet battery has 3 cells. A 6 volt dry battery has 4 cells.
No
if it is any think over 1 volt it is not a cell battery it is just a 6 volt battery if you had a 1 volt then it would be a cell battery
Impossible to do with a single 6 volt battery.
If you are asking the question, can you charge a 6 volt battery with a 12 volt charger, the answer is no.
No, you cannot charge an 8 volt battery with a 6 volt charger. The voltage of the charger must match the voltage of the battery.