5 kW inverter on 48 V batteries: circuit sizing (NEC 706)

A 5 kW inverter on a 48 V battery bank draws 104.17 A continuous at full output. Battery-to-inverter conductors and their overcurrent device must be sized at 125% of that continuous current: 130.21 A minimum (NEC 706.30 applies the standard continuous-load rule to ESS circuits; same math as 210.19(A)). The device also has to be a standard rating — 150 A is the smallest rung that qualifies (240.6(A)), and for battery circuits it must be DC-rated at the system voltage.

Article 706 requires a readily accessible disconnecting means for the ESS, within sight or lockable-open, marked with nominal voltage and available short-circuit current. That marking is not busywork: large LiFePO4 banks can deliver fault currents that exceed the interrupt (AIC) rating of bargain fuses — the OCPD's AIC must exceed the computed available fault current at its terminals.

Practical trap: 104.17 A continuous at 48 V is unforgiving of undersized lugs and long runs. Voltage drop at 2% on a 48 V bank is only 0.96 V — keep battery-inverter runs short and verify terminations are rated for the conductor size and temperature.