Two 12 volt batteries in parallel give you 12 volts. Take two batteries and connect them in parallel.
Help Wiring 4 12volt Batteries To Make 24 Volts Passive
Connecting two 12 volt batteries in parallel. If the input rating on the inverter no matter what the output wattage says 12 volts you must only connect two batteries in parallel. Two 12 volt batteries wired in parallel continue to produce 12 volts but the capacity doubles. Two 12 volt batteries wired in series produce 24 volts but the capacity remains the same as one for a 12 volt battery. Four 12 volt 2000 mah wired in parallel can provide 12 volt 8000 mah 2000 mah x 4. Take another set of batteries and wire them together in parallel as well. Use one battery cable.
Finally take a jumper wire and bridge the positive terminal of one parallel connection to the negative terminal of the second parallel battery pair. The parallel connection of two identical batteries allows to get twice the capacity of the individual batteries keeping the same rated voltage. Connecting them in series will seriously damage the inverter. Batteries may be wired in parallel or in series. Two 12 volt batteries in series give you 24 volts. But what happens if you wire batteries of different voltages and amp hour capacities together in parallel.
This is the big no go area. Connecting batteries of different voltages in parallel. Charging 12 volt batteries wired in parallel requires a 12 volt battery charger. Following this example where there are two 12v 200ah batteries connected in parallel we will therefore have a voltage of 12v volts and a total capacity of 400ah ampere hour. Make a parallel connection for the two 12 volt batteries. Connect the two positive terminals on both batteries together.
Attach the positive terminals together and the negative terminals together.