Both chemistries are safe when properly engineered and maintained, but the risk profile differs. Lead acid batteries can off-gas hydrogen during charging and contain corrosive sulfuric acid electrolyte, which poses spill and handling risks. Lithium batteries don't off-gas the same way and have no liquid acid to leak, but they do require a properly engineered battery management system (BMS) to manage cell balancing, overcharge protection, and thermal limits. A well-designed BMS is what separates a safe, long-lasting lithium pack from a poorly engineered one — Vollterra's cells are built with [insert specific BMS/thermal safety architecture details] to manage this at the pack level.