cell_chandra

The Bolt pack entry should flag one chemistry distinction that matters practically for salvage buyers: the pre-recall (2017–2021) packs use LG Chem NMC, while the replacement packs distributed under the recall campaign use a reformulated NCMA cathode — nickel cobalt manganese aluminum. These are not the same material and the performance profile differs in ways worth understanding. NCMA adds roughly 5% aluminum substitution at the nickel sites. That substitution meaningfully improves thermal stability: onset temperature for thermal runaway in NCMA is approximately 40–50°C higher than in NMC 811. NCMA also shows better calendar aging in accelerated life testing because the aluminum stabilizes the layered oxide structure against the phase transitions that drive capacity fade in high-nickel cathodes over time. The tradeoff is slightly lower peak energy density, which GM accepted because the stability gain outweighed it for the automotive application — and because the Bolt fire incidents were specifically related to the NMC chemistry under certain conditions. From a salvage buyer's perspective: a post-recall replacement pack is chemistry-meaningfully different from a 2018 original pack, and generally in a favorable direction. When comparing pricing between Bolt packs, it's worth asking the seller whether the pack is original or a recall replacement. The answer affects both safety profile and expected longevity — and because GM did the thermal system revalidation for the new chemistry, the cooling calibration on the replacement modules is specifically matched to NCMA behavior. That's not a trivial difference if you're repurposing the pack's original BMS hardware.