charging a 12v battery with a 36 volt Battery Bank. Possible? Easy or Hard?

Thread Starter


Joined Mar 22, 2011
I am curious about the possibilities of using a 36V Deep Cycle Battery Bank to Maintain and charge a 12Volt Deep cycle battery?

My goal is to have a system that has both 36v and 12v applications. The goal is to have one point of recharge in the system from an outside source.

I would like to be able to recharge the 36V Bank and have it maintain and charge a 12v bank.

I don't want to jump into the 36v series at the 12v point in the series to do this. Which I don't know is even possible for charging but I know is doeable if I want to pull 12v power from the series but highly Not recommended. I know that the inequality this creates within the series will degrade the bank faster.

What are my options on a DC to DC charger?

My project.

I have a Golf cart using as a work vehicle that has a 36v Battery (Six 6V batteries in series) I want to add an ac Inverter to the Vehicle, I know I can get an AC inverter that works off of 36v but I don't need that expense.

I want to simply add in a 12v battery for which there is a free space within the golf cart that the battery will fit nicely, that I can use to run the AC inverter plus I will be able to run 12v accessories like lights and add a cigarette power socket to power other stuff without adding a 36v to 12v Buck Converter and also without draining my 36v bank.

I also don't see this charging system as being connected full time. I see that when I plug in the 36v charger I would flip a switch and activate the 12v charging system too.

One pitfall I see to this is that I would be using a 36v Auto Shutoff charger, and if I add some kind of 12v charging circuit to the 36v system I could run into a current draw from the 12v charging system even after fully charging the 12v battery that would cause the 36v charger not to trip off when full.

What are the ease of doing something like this? Other Negatives?

I really don't want to plug in two different chargers as I want portability of only having the single 36v charger so i can go from location to location that is why I am looking at this solution.

Thank You.


Joined Dec 25, 2008
A buck charger would be best but since you don't want to do this you may consider using a simple linear voltage regulator with current limit. If you don't limit the current you could run into serious over-current problems when the 12 volt battery is quite low. Don't forget that charge voltage for a regular 12 volt lead-acid battery is about 13.7 volts to float and 14.4 volts for a quick charge. You might get away with 13.7 volt regulation limited to say, 5 to 10 amps. Because of the linear regulation you'll get some heating of components.