What Causes a Car Battery to Not Charge?

[VanMatthew]

The reason a car battery fails to charge is due to sulfation of the plates, which refers to the excessive deposition of lead sulfate on the internal plates of the battery, leading to increased internal resistance and reduced capacity. The functions of a car battery include: 1. Providing power to the starter and ignition system; 2. Supplying stable DC power to electrical devices; 3. Stabilizing the voltage of the AC power generated by the alternator. To diagnose a car battery that won't charge, check the following: 1. The connection lines and plug contacts of the charging circuit; 2. Whether the charger is damaged and the parameters of the charger; 3. Whether the battery is dry or lacks electrolyte; 4. Whether the plates are sulfated.

[LillianaFitz]

I've encountered this situation many times while repairing vehicles. There could be multiple factors preventing charging. The most common issue is charger malfunction, such as loose plugs or damaged internal components, which prevents current transmission. Another possibility is problems with the car battery itself - if it's been used for several years and has aged, with dried-up internal electrolyte or corroded electrodes, recharging won't help. Poor wire connections, like rusted terminals or dirt blockage, can also increase resistance. Low ambient temperatures can reduce charging efficiency too, just like how batteries struggle to hold charge in winter. I recommend first checking the charging equipment - try a new charger. If that doesn't work, test the battery voltage; it should normally be above 12V. If it's lower, the battery might need replacement. Regular cleaning of battery terminals during maintenance can extend its lifespan.

[ChaseLee]

I often deal with similar issues when repairing cars, and the key is to troubleshoot step by step. First, confirm whether the charger is functioning properly and test the socket voltage. If the battery terminals are loose or severely corroded, use sandpaper to clean the connection points. Wiring faults like short circuits or open circuits can blow fuses, so check the fuse box and replace any blown parts. Alternator failure is also a common cause, such as a loose belt or damaged voltage regulator, which prevents the battery from charging. If you notice smoke or overheating, stop operations immediately to prevent accidents. Preventive measures include avoiding excessive battery discharge and regularly inspecting the electrical system to ensure driving safety.

[ColinRose]

My car also had this charging issue before, and the reasons were quite simple. First, the charger might be broken or not plugged in properly—try unplugging and reinserting it while checking the indicator light. Second, the battery could be too old, unable to hold a full charge after a few attempts; replacing it solved the problem immediately. Third, loose or corroded connections can interrupt current flow—cleaning them might help. Keeping the garage dry and well-ventilated is also crucial to prevent moisture from affecting the charging process. If the problem persists, it’s best to visit a professional shop for diagnosis to avoid minor issues turning into major faults.