The battery in any aircraft electrical system is asked to accomplish the following at any given time:

1. Deliver large flows of energy for short intervals in cranking the engine, and recover quickly from these processes,
2. Deliver many watt-hours of energy when used as a redundant source of electrical power in case of alternator failure,
3. Provide filtering and bus stabilization for the alternator,

and it must do so in adverse environments of heat, cold, strong vibrations, and various g-loads.

As the battery ages and is subjected to many starts and many hours of operation, the internal structure begins to slowly break down, and the internal resistance increases. The battery eventually succumbs to age and abuse. This inevitable decay erodes not only the battery's cranking power, but also more importantly its life and ability to store energy.

While the measured open circuit voltage is can still be nominal, the internal resistance rises; this results in decreasing efficiency in discharging and charging as energy is lost to the internal heating that results. Not only is capacity and cranking power reduced, but also the inefficiency of tapping the remaining capacity is significantly increased.

If we are to design an electrical system that will be failure tolerant, we must consider the battery's condition upon the possible failure of the alternator.

Therefore, I propose that the existing Concorde RG (recombinant gas) battery be placed on a mandatory replacement schedule of every 2 years.