Two 12 volt batteries to make 24 volts.
Connect one battery cable to the positive terminal of one of your 12 volt batteries.
Two or more 12 volt batteries wired in parallelpositive to positive negative to negativeis still a 12 volt system.
You now have two batteries connected in series.
Some larger trolling motors will require 36 volts by connecting together 3 deep cycle 12 volt batteries in series.
Connect the other end to the negative terminal of the second 12 volt battery.
By wiring a pair of 12 volt batteries in series you can use the same batteries to perform two different tasks.
Two or more 12 volt batteries wired in seriesthe positive terminal of one.
How to make a 12 volt battery 24 volts.
For example a boat may have a 12 volt starter for the main engine and a 24 volt trolling motor.
Use 12 volt batteries to run a 12 volt and 24 volt devices.
This is a common application needed to supply power to a trolling motor requiring 24 volts.