 Although Li-Ion batteries typically have shorter lifetimes than Ni-H2 batteries as they cannot sustain as many charge/discharge cycles before suffering notable degradation, the ISS Li-Ion batteries have been designed for 60,000 cycles and ten years of lifetime, much longer than the original Ni-H2 batteries' design life span of 6.5 years.The power management and distribution subsystem operates at a primary bus voltage set to "V"mp, the peak power point of the solar arrays., "V"mp was 160 volts DC (direct current).