Lesson 2/Learning Event 1
In order to increase voltage, the batteries are connected in series. Recall that in a series circuit the
current has only one path to follow; therefore, the same current will flow through all batteries when
they are connected in series. A series connection of two batteries is made by connecting the
negative terminal post of one battery to the positive terminal post of another battery. Batteries
connected in series should have the same ampere-hour rating. A voltage source equal to the sum
of both batteries is then available at the two remaining terminal posts. The ampere-hour rating of
batteries connected in series is the same as the smallest battery by itself. For instance, some trucks
use two 6TN batteries which are rated at 12 volts and 100 ampere-hours each. The batteries are
connected in series to furnish a power source of 24 volts and 100 ampere-hours.
In order to increase the ampere-hour rating, the batteries are connected in parallel. In a parallel
circuit the current has more than one path to follow. Batteries connected in parallel must have the
same voltage rating. To connect two batteries in this manner, the positive terminal posts of both
batteries are connected together and then the negative terminals of the batteries are connected.
Each battery will now furnish half the current flowing in the load so their ampere-hour ratings will
be added together, but the voltage will be the same as one battery alone. The parallel connection
of batteries when used in tactical wheeled vehicles is combined with the series connection and is
known as the series-parallel connection.