What causes the auxiliary battery failure in Mercedes-Benz E300?
2 Answers
Mercedes-Benz E300 auxiliary battery failure causes and solutions are as follows: Circuit failure: The main issues are battery damage, circuit failure, or control circuit problems. Solutions: First, check the generator's belt and plug to see if they are loose, as poor contact caused by looseness can be resolved by tightening. Check if the battery is dead; if so, recharge it. For specific situations, it is necessary to go to a 4S store for professional inspection and then determine the repair based on the results. The battery of the Mercedes-Benz E300L is located at the rear right corner of the engine compartment, and the battery can be seen by opening the plastic cover above it. The auxiliary battery is a very small backup battery, model: 12v, 12AH battery, which is an emergency power supply battery.
My Mercedes-Benz E300 had an auxiliary battery warning last year, which turned out to be mainly due to battery aging. The auxiliary battery in this car is usually installed under the front passenger footwell or in the trunk compartment, specifically powering the start-stop system and onboard electronics. Frequent start-stop cycles in daily driving consume significant power, and if you often take short trips, the alternator may not fully recharge the battery, leading to power depletion. Once when I was away on business for half a month without driving, the car immediately showed a fault upon return, with voltage dropping below 10V. I recommend turning off the auto start-stop feature during normal starts to reduce load. The auxiliary battery typically lasts 2-3 years - when warning alerts appear, it's best to promptly check the charge/discharge current. If internal resistance exceeds standards, replacement is needed. Also, try to avoid installing always-on devices like 24-hour dashcams that continuously drain power.
