Question? Help please

[endean0]

Can anyone help please.

If I connect 3 car batterys together and start charging them, will all three take a charge or only the first one, or possibly one at a time after the first has become fully charged?
Would the way they are connected make any difference, parrallel or series?

Thanks

 

[Nigel Goodwin]

Can anyone help please.

If I connect 3 car batterys together and start charging them, will all three take a charge or only the first one, or possibly one at a time after the first has become fully charged?
Would the way they are connected make any difference, parrallel or series?

If you connect any batteries in parallel they will feed current from the higher charged one to the lower one, until all the batteries are balanced - if the batteries are permanently connected in this way it doesn't matter too much. But if you're intending coupling three batteries together just for charging it's something to be aware of - best to feed each battery through it's own blocking rectifer to prevent it.

Having done this, the lowest one will take most (if not all?) of the current initially, as the charge on that one rises the others will start to get more of the share - eventually they 'should' reach equal levels of charge, and hopefully will share the charging current between them. I'm presuming the three batteries are absolutely identical?, and in a similar state of health?.

Personally I would advise providing seperate charging circuits for each battery, it could be as simple as a resistor and blocking rectifer feeding each one seperately from a common charger.

In series different concerns apply, but again, if they are normally used in series it would be fine - and, in actual fact, this is how the battery itself is constructed - six 2V cells connected in series to give 12V.