In E-latch designs where more than one supercapacitor is stacked in series, a cell balancing circuit is recommended to equally distribute the total stack voltage among the supercapacitors. Cell balancing is essential for supercapacitors connected in series because even small variations in capacitance, leakage current, or internal resistance between the supercapacitors can cause uneven voltage distribution. Without balancing, some of the supercapacitors can be driven above the rated voltage during charging, leading to accelerated aging, reduced capacity, or even catastrophic failure. Balancing maintains that each supercapacitor operates within safe voltage limits, improving reliability, extending service life, and maintaining consistent performance. This preventive measure is especially important in automotive applications, where the cost of failure or maintenance is significant.

For designs using up to seven supercapacitors in series, the BQ76907-Q1 provides a highly integrated, high accuracy design for monitoring, protecting, and balancing of individual caps in a series stack. If a safety-rated device is needed, the BQ78709-Q1 is a similar device with an ASIL-B rating.