What is a parallel circuit?
A parallel connection or circuit is used to increase capacity. By connecting two or more batteries in parallel, their total output power (Ah) is added up while their voltage (V) remains the same. To connect the batteries in parallel, the positive terminal of one battery is connected to the positive terminal of the next, while the negative terminal of the first battery is connected to the negative terminal of the next. To provide an example: if 10 batteries rated for 12V at 50Ah are connected in parallel, this creates a battery system capable of supplying 12V at 500Ah. One should always remember to use connecting cables of the same thickness and length when building a parallel circuit.
As with series circuits, the batteries with different capacities (Ah) or voltages (V) may never be connected to one another in parallel. Besides using batteries rated for the same capacity and voltage when creating a parallel circuit, Intercel recommends using only batteries of a single brand.