The MOPS have a higher threshold for failures than the 787 special conditions, however, as allowances for unsafe cell temperature and pressure excursions and explosive or toxic gas accumulation are made only for “extremely improbable” failures of the equipment, a threshold generally reserved for catastrophic failures. In FAA parlance, that equates to one failure in 1 billion flights, or 100 times more infrequent than the extremely remote failure case in the 787 special conditions.

Worst-case tests the RTCA recommends include an “induced destructive overcharge with protection disabled test” that looks for “any evidence” of flames from the battery for 3 hr. after the overcharge source is removed, and “effectiveness of the battery containment case to contain all debris resulting from any explosion during or after the test”.