A parasitic load is a small, continuous flow of DC current that takes power from the battery even when the aircraft master switch is turned off. Parasitic loads are present, to a greater or lesser degree, in almost all modern aircraft. Examples of parasitic loads are relays, clocks, radios, and on-board computers. These loads are generally low amperage (e.g., under 50 milliamperes), but since they are continuously present they can deplete the battery’s capacity if the aircraft is inactive for an extended time. One of the inherent dangers is that a battery without enough emergency power reserve can often still start the engine(s).

A long term, low drain rate can deeply discharge the battery, deeper than what can occur with normal aircraft loads. Repeated deep discharges of this nature will shorten the battery life substantially. A battery deeply discharged in this manner may not be recoverable with normal charging methods. If the parasitic drain is high the battery will become completely discharged in a few days and render the aircraft inoperable causing an AOG event with unexpected expenditures for obtaining an urgent replacement, freight and installation.

Concorde Battery Corporation’s Parasitic Load Test Adapter (PLTA) makes it easy to measure the parasitic load of aircraft batteries equipped with an MS3509 Style quick disconnect receptacle. The Parasitic Load Test Adapter is designed to connect between the battery receptacle and the aircraft’s mating plug, with separate test leads for connection to a calibrated digital multimeter.

For more information on the PLTA please download the Parasitic Load Tester Instruction Manual from www.concordebattery.com. To purchase a PLTA, contact a Concorde Battery Distributor and ask for part number 4102.

Concorde Battery Corporation
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