Each 12 volt 100 amp hour battery is connected to the adjacent battery in series to make 24 volts. Then, each 24 volt pair is connected in parallel to the next 24 volt pair underneath. You can connect additional batteries using this method with as many pairs as you would like.
Parallel wiring connections are made by connecting a positive terminal (+) to a positive terminal (+) and a negative terminal (-) to a negative terminal (-).
Next, connect your charging and load cables on opposite corners of the battery bank as shown below for even charging distribution. Your load connections are made to your inverter or other power draw (load) away from your batteries.
Each 12 volt 100 amp hour battery is connected to three more batteries in series to achieve 48 volts. Then, each 48 volt string of batteries is connected in parallel to the next 48 volt string of batteries underneath. When you connect batteries in parallel, the opposite of series connections happens. The voltage will remain the same, but the amp hours will double. Again, make your positive and negative charging and load connections at opposite corners of the battery bank for even distribution.