take care,make sure you can identify the the positive and negative,if theres no colours or markings ,the positive is the larger terminal,,,,hook one battery positive ,to the other ones negative,,that leaves you with positive free on one battery ,and one negative free on the other,this will double the voltage to 12 volts,you can use these free terminals as one 12 volt battery,if you do this with a pair of 12volt batteries you will have 24 volts as used on many trucks,,,if you hook the positive to the positive,and the negative to the negative with your 6 volt batteries ,,the voltage will stay the same but it will be like a higher capacity battery.,same for 12 volt batteries
