Lead acid 12 volt batteries are used for many different purposes, not just as automobile batteries. Solar power systems and starting systems for heavy machinery are two such examples. Depending on the size of the system and the power needed, one or more batteries can be connected together to provide the additional power. In a 36-volt system, three 12-volt lead acid batteries are connected in series to form a 36-volt string. Connecting batteries together requires only a few tools.
Set three lead acid batteries side by side. Using a permanent marker, label the first battery B1, the second battery B2 and the third battery B3. This will make it easier to reference each battery.
Loosen the clamps on two battery cables so that they will fit over the battery posts easily. Connect one end of one battery cable to the negative post of B1, which will be marked with a minus sign. Connect the other end of that same battery cable to the positive post of B2 (marked with a plus). Tighten the clamps on both of these posts using a socket wrench or box wrench.
Connect one end of the second battery cable to the negative post of B2, and connect the other end to the positive terminal of B3. Tighten the clamps on both posts. This finishes connecting the batteries in series. Voltage for this unit is measured across the positive terminal of B1 and the negative terminal of B3.