How to Test Whether a Battery is Good or Bad?
2 Answers
Battery monitoring methods for determining quality are: 1. Inspect the exterior: Check whether the battery casing is bulging, leaking, has broken separators, or corroded terminals. If any of these phenomena are present, it indicates the battery is dead; 2. Measure voltage: After charging for two hours, measure the voltage of individual battery cells at 20-minute intervals. If the voltage is below 13V, it indicates a problem. During discharge, measure the voltage three times at 10-minute intervals. If the discharge time is faster than other batteries and the voltage drops below 10V, the battery has an issue; 3. Check for water loss and blackening: After charging the battery for 36 hours, if the charger's red light remains on, it indicates severe water loss. Open the battery's top cover to reveal six circular holes. Check the color of the electrolyte in each hole. If it appears black, it means the lead powder from the plates has shed, indicating the battery is dead.
My most common practice is to use a multimeter to measure voltage—it's simple and reliable. Set the meter to DC voltage mode, connect it to the battery's positive and negative terminals, and it should normally display 12.6 volts or higher. If the reading drops below 12 volts, the battery might be failing soon, so try charging it immediately. Then perform a load test—for example, measure the voltage while turning on the headlights or the AC fan. If the voltage drops sharply, it means the battery can't handle the load. I also regularly check the battery's exterior for cracks or leaks and inspect the terminals for oxidation or corrosion—cleaning them can extend the battery's lifespan. Car batteries typically last three to four years before aging, especially prone to issues in winter. Detecting problems early and replacing the battery can avoid the embarrassment of a roadside breakdown, saving both hassle and money.
