Free Battery Runtime calculator with clear step-by-step results.
Converts a battery's amp-hour rating into real runtime. Nameplate capacity is derated by the depth of discharge you are willing to use and by inverter losses, then divided by the load in watts. The DC current figure tells you whether your cabling and fusing are adequate for that draw.
Usable energy
Usable Wh = Ah x V x depth of discharge x inverter efficiency
Runtime
Hours = usable Wh / load watts
Battery installations involve fire and electrical shock hazards. Sizing, fusing and ventilation must follow the manufacturer's specification and local electrical code.
Lead-acid banks lose most of their cycle life below 50% discharge, and even lithium packs reserve headroom. The depth-of-discharge field is what keeps the estimate honest.
Yes, for lead-acid. Peukert's effect means a heavy draw yields fewer usable amp-hours than the 20-hour rating suggests. Lithium chemistries are far less affected.