• The JFM Engineering Battery Shop is equipped with our own Charger-Analyzers and our own computerized Data Acquisition and Charger-Analyzer control system, both characterized by high accuracy and precision.

• Battery service is performed under stringent procedures geared to returning battery performance as dictated by the battery and airframe manufacturers.
  
• All test details are fully recorded and they are maintained in our electronic database and paper filing system.

• Our Battery Shop is affiliated with Satair-Aero Quality Sales, which gives us access to all required cells and other replacement parts.
  
• Tests performed:

Note: Description of tests refer primarily to Nickel-Cadmium batteries. Additional comments are provided for Lead-Acid batteries.

Top charge:

    Top charge is the simplest type of service for all types of batteries. Batteries are "topped off" before being put on the aircraft to compensate for self-discharge while in storage. Top charge is also used to determine the proper electrolyte level. Water is normally lost during usage and it is also lost due to evaporation. When the battery reaches full charge, the electrolyte is at its maximum level; distilled water is added as required.
    The top charge process is also used to measure cell voltages, to determine that each cell reaches the proper charge voltage and to check if any cells exhibit a temperature rise and/or drop in their voltage under constant charge current (topping current).
    Lead-Acid batteries are also top charged, and if of the flooded type, the specific gravity and level of electrolyte is also tested and adjusted as necessary. On sealed batteries, the specific gravity of the electrolyte cannot be measured.

Capacity Test:

    This is the most important test, for it determines if the battery is fit to return to service. After receiving a full charge, the battery is subjected for one hour to a typical discharge current of 100% of its rating. If none of the cells drop below 1V, the battery passes the capacity test. It is then recharged and returned to service. If one or more of the cells drop below 1V (even if the battery as a unit does not drop below 20V) the battery fails the capacity test.
    What happens next depends on the individual condition of the cells. If the cell voltages are reasonably similar (balanced), the battery is recharged and re-tested for capacity. If the cells are heavily unbalanced, then, the battery is subjected to a full discharge (deep cycle).
    If after three tries, one or more cells fail to meet the capacity test, they are replaced. If more than 20% of the cells need to be replaced, it is recommended that either all the cells be replaced or that the entire battery be replaced .
   Lead-Acid batteries are similarly tested for capacity, but with no individual cell readings (terminals for individual cells are not available).

Deep Cycle:

    A battery where the cells are heavily unbalanced, either as received for testing or after failing a capacity test, must be fully discharged. This allows all cells to start from zero in the subsequent recharge, thus restoring the balance in the cell voltages.
   Lead-Acid batteries are never discharged to zero during testing

Overhaul:

    Batteries are not repairable, at least not with the same meaning that we apply to other devices. The basic component of the battery is the cell (or cell block in a Lead-Acid battery). If cells fail to perform, they are replaced. The same is true for other parts such as temperature sensors, connectors, links and fasteners.
    A battery received for overhaul will get fully disassembled and washed. Cells will be inspected for leaks and burns. Interconnecting hardware, (connectors, links, screws, nuts and washers), are normally cleaned. If burned or corroded, they are replaced.

3 - Battery Testing Consulting

JFM Engineering can assist you with consulting support for the establishment of a Battery Testing Facility and with training in Battery Testing

4 - Articles on Battery Testing

Aircraft Battery Testing Definitions and Notes
Battery Testing Guidelines
Importance of Water Leveling
Series Testing of Nickel-Cadmium Batteries