New Aircraft Battery Parasitic Load Tester from Concorde

Concorde Battery Corporation has released a new Parasitic Load Tester (PLT) to measure the parasitic load / drain on aircraft batteries when the master switch is off and the aircraft is inactive. The tester is designed to mate with a MS3509 style quick disconnect receptacle. This innovative PLT was conceived and engineered in response to concerns in the aviation community about the effect of parasitic loads / drains on battery capacity, state of charge, airworthiness and battery life.

A parasitic load is a small, continuous flow of DC current that takes power from the battery when the master switch is off. Parasitic loads are present in most modern aircraft to some degree. Examples of parasitic loads are relays, clocks, radios and on board computers. Depending on the magnitude of the parasitic load, the battery in an inactive aircraft may be depleted within weeks or even days. A battery discharged in this manner can cause an AOG event. Another inherent danger is that a battery without enough emergency power reserve can often still start the engine(s), leaving you vulnerable in the case of a generator failure. The FAA requires aircraft batteries to be certified with a minimum of 80% capacity for emergency power reserve in the event of an electrical generating system failure.

Repetitive deep discharges from parasitic drain will shorten the battery life and batteries deeply discharged in this manner may not be recoverable. If authorized by the aircraft manufacturer, disconnecting the battery from the battery plug when the aircraft is stored will eliminate the parasitic load.

Measuring parasitic load is easy to do by connecting the PLT between the battery receptacle and the aircraft mating plug. The PLT is a molded polypropylene body equipped with separate test leads for connection to a digital multimeter (DMM). Concorde PLT part number 4102, is rated for loads up to 10 amperes and is equipped with a 10 amp fuse.

Instructions on how to measure parasitic load and calculate time to battery depletion are provided in Instruction Manual, Aircraft Battery Parasitic Load Tester, Document No. 5-0409. The manual is packaged with the PLT and is also available online at

Concorde Battery Corporation manufacturers over 90 lead acid aircraft battery models designed for Original Equipment or direct replacements. Certifications and approvals include Type Certified, TSO-C173 & FAA-PMA. Concorde’s recombinant gas and absorbed glass mat technology has been proven and adopted for use on military and commercial aircraft worldwide since 1987. Concorde manufactures to ISO 9001 + AS9100 quality standards.