Actual service life really depends on the operation.

The batteries are made up of proven components with a high reliability.

Calculated MTBF (Mean time between failure or service life) is not applicable to batteries. The actual reliability of the battery system will be directly dependent on the manner in which the user operates the aircraft, the actual conditions in which the aircraft operates, and the accidental abuse to which the battery may be subjected.

The primary cause of battery failure in aircraft is due to customer abuse. This comes in a wide variety of forms including as follows: Overcharge, over-discharge, allowing a discharged battery to stand for several days before recharging, and cycling the battery repeatedly by allowing parasitic loads when the master switch is off are the most prevalent. It is for these reasons that we cannot really make one blanket statement to cover all operations.

With that in mind, where the battery continues to perform and test well, we recommend you replace it after four years. The battery may actually still be fine at that point, but as they age the issue is vibration induced fatigue. Batteries are subjected to a reduced vibration standard since they are short life components. The probability of something breaking internally in the battery resulting in an open circuit (no power) increases as the battery ages and is subject to more cycles of landing and in flight vibration.