Lead-acid batteries linked in series provide larger amounts of voltage than a single battery provides. In a series circuit, the voltages of batteries linked together is cumulative. For example, two 12-volt batteries provide 24 volts, and three 6-volt batteries provide 18 volts. Boats, golf carts and some cars use several relatively cheap low-voltage batteries to do the job of a very expensive higher-powered battery. Charging batteries linked in series is straightforward but requires higher-voltage charging equipment.

 

1. Count the number of lead-acid batteries linked together. Determine the voltage of a single battery. The voltage will be printed somewhere on the battery casing, and each batterycharger should have the same voltage. Multiply the number of batteries by the voltage of a single battery to find the total voltage. For example, eight 6-volt batteries linked in series give a total voltage of 48 volts because 8 multiplied by 6 equals 48.

 

2. Determine whether the batteries are maintenance-free. Look on the casing for information about the type of battery. Batteries that are not maintenance-free require checking before charging to ensure that they contain sufficient electrolyte. Unscrew the vent caps that form a line along the top of a battery that's not maintenance-free. Each cap, when removed, allows a view into the battery. If the metal plates are showing above the liquid, top up using either battery water or deionized water. Fill until the plates are just submerged. Loosely replace the caps, but do not tighten them.

 

3. Charge the line of batteries using either one charger for each battery in the line, or connect a charger, rated for the total voltage of the batteries, across the unused terminals at opposite ends of the linked batteries. If you use one charger with each battery, connect them as if each battery was a stand-alone battery being charged normally. High-voltage chargers designed to charge strings of serial-linked batteries are available from boating, solar power and golfing supply stores. Sizes up to 60 volts are common.

 

4. Disconnect the charger when the built-in charge meter indicates that charging is complete. Do this by switching off the power to the charger and then disconnecting the charger leads from the battery. Tighten any vent caps loosened in Step 2.