How to charge lead calcium batteries

battery charger image by Albert Lozano from

Vehicles use lead-acid batteries to provide a 12-volt power supply. Lead is a very soft metal so it must be strengthened by adding other chemicals. Calcium not only hardens the lead but also reduce the production of hydrogen gas when the battery is charged. In the early 1970s, lead-calcium batteries were installed as "maintenance free" batteries because less hydrogen gas resulted in the electrolyte lasting much longer. Lead-calcium batteries needed to be charged at a higher voltage, almost 15 volts and with a special "Type IU" charger.

Disconnect all the leads attached to the battery. Place them somewhere where they cannot drop back onto the battery terminals. With the leads positioned out of the way, use a cloth and a wire brush, if necessary, to clean any dirt and corrosion from the terminals until the metal shines.

Check the level of electrolyte in each cell. Remove the vent caps on the top of the battery and use a flashlight to check the level of the liquid in each cell. If the tops of the metal plates are above the liquid surface, check the manufacturers' guidelines, and then top up the cell with battery water or deionised water. Replace the screw caps, but don't fully tighten them.

Ensure the battery charger is not connected to the electricity supply.

Attach the battery charger leads to the battery terminals. The red positive lead goes to the positive terminal, and the black negative lead to the negative terminal.

Connect the charger to the power supply, and then switch it on. Leave the battery to charge, checking occasionally to ensure it is not hot or making bubbling noises. When the charger indicates that the battery is fully charged, switch off the charger, remove the charger wires and tighten the vent caps on the top of the battery.

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