A mobile robot is limited by what it can carry, and power is often the tightest constraint. Battery management tracks charge, manages temperature and plans around the fact that every sensor, motor and computer draws from the same finite store.
Smart systems route robots to charge during natural lulls and balance performance against endurance, since running flat out shortens working time. How gracefully a fleet handles charging, without leaving gaps in the work, often matters more than the raw capacity of any single battery.