I have 6 12 volt car batteries hook up to produce 72v. I have seen chargers that can be connected to each battery and charged at 12v each while the batteries are still series and using the 72v from them. But they are expensive. What kind of circuit would it take to do this from 12v to charge the batteries while still using the 72v.
Thanks Ed

 

What it takes is six (6) seperate transformer windings driving six (6) seperate brain circuits to keep the batteries from connecting to each other through the chargers. The cheap way might be to buy 6 cheap 12V chargers and make sure they do not have their charging leads connected to the metal case or earth ground (in the power cord).

Is that what you needed?

 

How are these new charges setup to do this. If I would use diodes to each lead going to battery to charge would this work or is there circuit I could build other than having 6 transfomers.
Thanks Ed

 

6 different chargers would be "set up" by connecting one to each battery. Diodes will not fix the isolation problem. A circuit to do this would be a 72 volt battery charger, but that is exactly what you were trying to avoid in the first question.

 

I have altenator that has 12v dc is the anyway to use that source to do this.

 

One 12 volt alternator will charge one battery.

 

If I would use the stator wires wired to 3phase bridges. I will work out the rest of circuit. Would that give me isolation?
Thanks Ed

 

Is this battery bank indoors? Or in the garage/workshop maybe?
Fire precautions/risk?

You can use 6 relays and only charge one battery a time, for some minutes.

If you don't take much current from the battery bank, this won't be an issue.

Isn't there another solution you can use? Why 6 batteries?

 

If I would use the stator wires wired to 3phase bridges. I will work out the rest of circuit. Would that give me isolation?
Thanks Ed

Nope, still no isolation. The only way to achieve isolation is to have six separate transformers (or alternators) or one transformer with six separate output windings.