One of the worst things that can go wrong with an aircraft is a dead battery. Aircraft batteries are used for many electrical functions, from the initial powering of the aircraft to a critical component of the electrical emergency systems.
Aircraft batteries have a shelf life and will naturally discharge a small amount every day that it is either in storage or unused in the aircraft. Like other aircraft components, proper storage, inspection, and maintenance procedures need to be performed to make sure the battery stays functioning properly for many years of dependable service.
Aircraft Battery Types
Aircraft batteries are usually identified by the material used for the plates. The two most common types of battery used are vented or sealed Lead-Acid and Nickel-Cadmium (NiCd) batteries. Most small private aircraft use lead-acid batteries. Most commercial and corporate aircraft use Nickel-Cadmium batteries. Other battery types include Nickel Metal Hydride and Lithium-Ion.
Choosing the battery best suited for a particular aircraft depends on several characteristics, such as weight, cost, shelf life, charging or discharge rates, and maintenance requirements. The differences in battery type use are significant, so changing to a new battery type may be viewed as a major alteration.
Aircraft Battery Inspection and Maintenance
The main reason batteries fail is that they are not regularly maintained. If the battery connections, water level, or the charge state are only checked at the annual inspection, battery failure will be likely. Regular maintenance is necessary to preserve the usefulness and performance of the battery.
Battery inspection and maintenance procedures and intervals can vary with the type of chemical composition, the type of physical construction and the temperature at which the batteries are stored. All maintenance should be done by following the battery manufacturer’s recommendations contained in the maintenance manual.
The mechanical integrity of the battery needs to be inspected regularly. This involves visually checking the battery for any physical damage, checking for corrosion or oxidation at the battery connections, and ensuring that the battery is properly connected. The battery cables can get hot if they are loose or the connections are dirty and do not allow a tight fit.
Aircraft Battery Storage
The optimum storage conditions for batteries depend on the battery type. Stored batteries are subject to discharge, breakdown of the chemical contents, and the electrolyte drying out which will cause the battery to lose its effectiveness. Heat accelerates each of these processes, therefore, it is recommended that the battery is stored in a cool, clean, dry, non-corrosive environment to maximize its shelf life. Batteries stored at a lower temperature can be stored longer, can reduce the time between required maintenance, and will save storage maintenance costs.
A temperature range of 5°C to 15°C is preferred for most battery types. The battery should be stored in such a way to avoid freezing of the electrolyte, which could permanently damage the battery. The battery should be fully charged when initially placed in storage and should be regularly tested to ensure that it does not reach a discharged state. If possible, the best way to keep a battery healthy while in storage is to connect it to a smart charger, which will only apply the appropriate amount of current required to preserve the life of the battery.
It is dangerous to store vented Lead-Acid and Nickel-Cadmium batteries in the same area. The chemical differences between the battery types can neutralize each battery causing permanent damage and rendering them useless. This potential for cross-contamination is reduced between sealed Lead-Acid and Nickel-Cadmium batteries, but generally, those types should always remain separated as well.