How to Charge Two 6V Batteries Wired in Series

Updated 12/23/2025 | Published 01/15/2019

Question:

What size battery cables do I need to attach two 6 volt batteries 220AH together and can I use a 12 volt charger to charge or do I need a 6 volt?

asked by: LeRoy

Expert Reply:

In order to connect your two 6 volt 220Ah batteries together in series I recommend using a minimum of 4 gauge wire on each terminal. In order to charge the batteries you can use either a 6 volt or 12 volt battery charger, it all just depends on how you want to charge them. If you want to charge both together then you will need to use the battery charger in 12 volt mode (if applicable) and at the end of the series. If you want to charge each battery separately then you will need to use the battery charger in 6 volt mode (if applicable) and on each battery.

In order to charge both batteries together I recommend using the NOCO Genius On-Board Battery Charger part # 329-GEN1 which will be prefect for your two 6 volt 220Ah batteries. Please note that as you are wiring the batteries in series the voltage will double but the output (Ah) will remain the same.

I have attached a photo for you as well.

expert reply by: Conner L