Autopsy of Battle Born LFP battery with the ‘thermal safety’ on the bus bar. (Credit: Will Prowse)After users of Battle Born LFP batteries encountered issues such as a heavily discolored positive terminal and other signs of overheating, multiple autopsies showed that the cause appeared to be the insertion of a thermoplastic between the bus bar and the terminal. Over time thermal creep loosened the connections, causing poor contact and melting plastic enclosures. According to Battle Born, this is actually part of an ingenious thermal safety design, and in a recently published article they explain how it works.The basic theory appears to be that if there’s a thermal event, the ABS thermoplastic will soften and reduce the pressure on the bolted-together copper bus bar and brass terminal. This then allows for an aluminium-oxide layer to form on the aluminium connecting bolt courtesy of the dissimilar copper/aluminium interface. Aluminium-oxide is non-conductive and thus interrupts the flow of current.Of course, there are countless issues with that theory, least of all the many reports of in-field failures. We recently covered [Will Prowse] studying the death of one of these 100 Ah LFP batteries from brand-new to failure under controlled circumstances. This clearly shows the thermal creep loosening up the connection and causing poor contact between the bus bar, the bolt and the terminal, with poor contact and thermal issues resulting.Naturally, [Will Prowse] had to address this most recent statement by Battle Born, with the latter taking care to indirectly attack and dismiss his findings. Here Battle Born’s argument seems to hinge on the removal of the lid damaging this aluminium-oxide layer and preventing the ‘thermal safety’ from working, yet not addressed are the many batteries that failed in the field and showed loose connections due to thermal creep from the ABS layer.It’s also never addressed why these LFP batteries cannot simply be equipped with a traditional thermal fuse rather than this convoluted contraption, among many other questions that remain. Correspondingly [Will] is rather incredulous at this response, as should anyone be who has been following this saga.