The CJ4's phosphate-based lithium-ion batteries weighed 30 lb. less than the equivalent nickel-cadmium battery that was available. Though packing about half the energy density of a cobalt oxide cathode battery, the phosphate-based chemistry has four-times the number of life cycles while having “inert” failure modes, according to Gallman.

The inertness of failure modes came into question however in the fall of 2011 when a maintenance worker hooked an “energized ground power unit” to a CJ4 battery and a fire reportedly broke out after thermal runaway in the battery. In early October that year, the FAA issued an emergency AD that required operators to replace lithium-ion batteries with the nickel-cadmium option.