How to Charge a Car Battery?

2 Answers
Devin
07/23/25 8:26pm
Methods for charging a car battery: 1. Connect the positive terminal of the battery to the positive terminal of the power source, and the negative terminal of the battery to the negative terminal of the power source; 2. The initial charging is carried out in two stages: First, charge with the initial charging current until the electrolyte releases bubbles and the single-cell voltage rises to 2.3 to 2.4V. Then, reduce the current to half of the initial charging current and continue charging until the electrolyte releases intense bubbles, and both the characteristics and voltage remain stable for 3 consecutive hours. The total charging time is approximately 45 to 65 hours. It should be noted that a new battery often does not reach its full capacity after the first charge, so a discharge cycle should be performed. Discharge at a 20-hour rate, i.e., discharge with a current equal to one-twentieth of the rated capacity until the single-cell voltage drops to 1.75V, and then recharge until fully charged. If the capacity is still below 90% of the rated capacity after one charge-discharge cycle, another charge-discharge cycle should be performed.
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McJune
08/10/25 6:25pm
I think car battery charging is quite common and should be done step by step. The preferred method is driving: when the engine is running, the alternator charges automatically, so frequent long-distance driving can maintain the battery level. The second method is using an external charger, suitable for situations where the battery is dead and the car won't start. When operating, first park and turn off the engine, find a ventilated place, and wear protective goggles. Then connect the charger: red wire to the battery positive terminal, black wire to the negative terminal or a metal part of the car body to avoid sparks. Set the charger to the 12V standard and choose the slow charging mode for the safest option, taking about 8-10 hours to fully charge a standard battery. Don't forget that fast charging, although quick, can damage the battery, so avoid frequent use. Also, safety precautions: don't smoke nearby while charging, as hydrogen gas may cause an explosion. I usually check if the battery terminals are clean and remove any corrosion; regularly test the voltage to ensure it's not undercharged, and charge more frequently in winter to prevent freezing. A tip to extend battery life is to avoid frequent short trips that drain the battery, and buying a smart charger with a maintenance mode is very convenient.
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