Wh to mAh Calculator

Battery energy storage systems (BESS) on commercial sites are specified in kWh at the system level but built from cells and modules rated in mAh at a specific voltage. Converting watt-hours to milliamp-hours at the cell voltage is the working calculation behind every BESS proposal, every IoT power budget and every standby battery bank specification. A 100kWh BESS built from 3.2V LFP cells needs around 31,250 Ah of cell capacity at the cell level, distributed across series and parallel strings to hit the system voltage.

For Industrial & Commercial operators using BESS to manage MIC headroom, capacity charges, triad-replacement charges or to shift load off peak periods, the modular sizing question drives the capital cost. A 500kWh BESS rated for a 1C discharge can offset 500kW of demand for an hour, which is enough to ride through the worst of a winter evening peak on a manufacturing site. Get the cell-level capacity right and the system delivers the bill saving the financial model promised. Get it wrong and the system underdelivers in the first cold snap.

Purely Energy works with clients designing BESS into their procurement strategy. We model the bill saving from MIC reduction, capacity-charge avoidance and time-of-use arbitrage alongside the supply contract itself, so the BESS investment case stands up against the alternative of buying capacity from the grid. For IoT and comms power budgets on remote industrial sites, the same calculation supports the design of standalone solar plus battery installations that keep monitoring kit running through the winter without a mains connection.