Concorde aircraft batteries are valve-regulated, recombinant gas, absorbed electrolyte, lead acid batteries. Positive and negative plates are tightly packed and sandwiched between layers of absorptive glass mat (AGM) and proprietary PolyGuard® separators.  The AGM consists of a blend of glass fibers of varying length and diameter that have superior wicking characteristics promoting maximum retention of electrolyte and minimum resistance to ion movement.  The PolyGuard® is a thin micro porous polyethylene layer that surrounds the AGM layer providing an extra barrier against plate-to-plate shorts for improved battery durability.  The dual AGM / PolyGuard® separator system is a unique feature of Concorde RG® Series batteries.


During manufacturing, cells are soaked with electrolyte, a mixture of sulfuric acid and water.   Electrolyte is absorbed within the pores of the plates and AGM separator.  The superior wicking characteristics of the AGM promotes maximum retention of the electrolyte. The electrolyte is held in place by the capillary action between the fluid and the glass mat fibers.  Excess electrolyte is then drained from the batteries. The glass mat remains 90-95% saturated but unlike flooded cells there is no “free” electrolyte.


On discharge, lead dioxide (PbO2) of the positive electrode and sponge lead (Pb) of the negative electrode are both converted to lead sulfate (PbSO4). The sulfuric acid (H2SO4) in the electrolyte is an active component in the reaction at both electrodes. On charge, the lead sulfate in the positive electrode is converted to lead dioxide (PbO2) and oxygen is also produced by electrolysis of the water. The void space in the AGM provides channels by which the oxygen travels from the positive to the negative plates. When the oxygen reaches the negative plate, it reacts with the sponge lead to form lead oxide and water.  This reaction at the negative plate suppresses the generation of hydrogen that otherwise would evolve from the negative plate. The recombination of oxygen and suppression of hydrogen virtually eliminates the escape of the gas from the cell, so topping up with water is never necessary over the life of the battery.


When flooded (vented) batteries are on charge, the charge current electrolyzes the water component of the electrolyte.  The oxygen generated at the positive plates escapes from the cell.  Concurrently, hydrogen is generated at the negative plates and escapes from the cell.  The overall result is the gassing of the cells and water loss, so periodic topping up with water is required.


Each cell is sealed with a pressure relief valve.  The pressure relief valve is designed to open when the internal pressure of a cell is approximately 1.5 psi above the external pressure.  The pressure relief valve prevents excessive pressure buildup when the battery is being charged, and automatically reseals once the pressure is released.  A slight bulge in the battery container can appear when the internal pressure increases slightly, but not enough to open the pressure relief valve.  Alternatively, if the pressure relief value opens at altitude and the battery is then returned to the ground, the external pressure can be greater than the internal pressure, resulting in a concave battery container.  Both of these conditions are normal and do not affect the battery’s operation.


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