High voltage energy systems for electric vehicles, and marine and home storage use series-connected lithium-ion battery packs that require battery management systems (BMS) to maintain cell output power, maximize life expectancy and for protection. Bourns reviews BMS market trends and design challenges. This paper highlights isolation of communications and transient protection solutions from isolated sigma delta converters with dynamic ranges less than 200 mV. It shows why shunt-based current measurement, signal and power transformers that feature double and reinforced insulation for high working voltages, and high-speed battery monitoring solutions provide crucial protection for IC A/D inputs.