Our ESS contains multiple overlapping safety systems – some active and some passive. Each module has its own microprocessor circuitry that monitors a wide range of conditions as well as actively balancing the cell voltage to help mitigate the danger of overcharging (and potential damage from over-discharge).
There are sensors inside the ESS that sniff for smoke,
check for the existence of water immersions (if the car were driven into a lake, for example), and continually monitor the pack to ensure that it is thermally stable. Each cell is independently fused, not once, but twice. And the pack has been designed to passively contain any single cell entering thermal runaway (e.g. start burning) without propagating further. (For more information on the Tesla Roadster's ESS, see our
blog and
white paper on the subject.)