How Long Does Battery Float Charging Take?
3 Answers
Battery float charging typically requires between 5 to 10 hours, and the charging duration should not exceed 12 hours to prevent potential battery deformation or damage. Float charging is a power supply mode for battery banks, serving two primary purposes: 1. Maintaining the battery voltage within the float charging range to extend battery life; 2. Compensating for capacity loss due to self-discharge and ensuring sufficient charge. During float charging, the charging equipment provides a constant load, supplying a small current to offset the battery's self-discharge and minor discharges caused by sudden load increases during short circuits. There are two types of float charging: 1. Periodic float charging power supply; 2. Continuous float charging power supply.
I just had my battery serviced recently. For regular lead-acid batteries, the float charging time mainly depends on the state of charge - severely depleted ones may require over 12 hours. If you don't drive often, it's recommended to use a smart charger for 8-10 hours monthly. AGM start-stop batteries are much more delicate - last time I charged mine at 0.1C current for 15 hours before the green light came on. Extra caution is needed during summer heat - my neighbor's battery swelled up just last week from charging. It's better to use chargers with automatic cutoff so you don't have to monitor constantly.
After ten years of car repair, I've found many car owners overcharge their batteries. The correct approach is: charge for an additional 1-2 hours after the charger turns green, which is sufficient. For example, maintenance-free batteries will definitely be oversaturated if charged for 15 hours. The key is to check if the battery's vent holes are blocked. Last year, a car's battery exploded due to overcharging, and the electrolyte corroded the entire battery tray. For newly replaced batteries, it's recommended not to exceed 10 hours of float charging for the first three charges. Remember to open the hood for ventilation during charging—safety first.
