Car battery chargers connect to car batteries with positive and negative cables and clamps, which are usually red and black and marked with a plus and minus sign. The positive clamps connect to the positive posts on the batteries themselves, and the negative clamps connect to vehicle frames or some other unpainted surface away from the battery.
Drivers should connect the positive clamp first and the negative second. Some vehicles are positively grounded, which means that the negative cable clamps onto the battery and the positive cable clamps to the frame. This information is included in the car's user manual. Keep the charger as far away from the battery as possible and only connect it when both the car and the charger are turned off and unplugged. Charge a car's battery following the instructions below.
Step 1: Read the instructions
Each charger varies, which means that different models may work in different ways. Chargers usually come with instruction manuals. Read the instructions carefully before plugging in their chargers and turning them on.
Step 2: Set the voltage and amperage
Following the instructions in their manuals, set the voltage and amperage on the charger. A low amperage charges more slowly, but the charge will last longer. A higher amperage is much faster to complete, but does not usually charge the battery fully. The voltage should correspond with the voltage on the battery. Drivers can usually find this information in their vehicle user manuals.
Step 3: Charge the battery and disconnect
To charge the battery, plug in the charger and turn it on. Once the battery is fully charged, turn off the charger and unplug it. Disconnect the cables, starting with the negative and finishing with the positive.