About Battery Bank Calculator

Calculates the series and parallel battery configuration needed for an off-grid or backup power system. You enter daily energy consumption, system voltage (12V–480V), battery specs, and desired days of autonomy. The tool accounts for depth of discharge and round-trip efficiency—which vary significantly between the six supported battery chemistries—to compute total batteries needed, wiring configuration, usable capacity, and estimated cost.

• Six battery chemistries with real-world parameters: lead-acid (50% DoD, 80% efficiency, 500 cycles), AGM (50%, 85%, 700), gel (60%, 85%, 1,000), LiFePO4 (80%, 95%, 3,000), Li-ion (80%, 92%, 2,000), carbon foam (70%, 90%, 3,500)
• Series count = system voltage ÷ battery voltage; parallel count derived from total required capacity after DoD and efficiency derating
• Days of autonomy factor multiplies required capacity—critical for sizing systems in areas with intermittent solar or unreliable grid
• System voltages from 12V (small off-grid) to 480V (commercial installations)
• Cost estimate based on battery count and user-entered per-battery price

Frequently Asked Questions

Why does depth of discharge matter so much?

A lead-acid battery rated at 100Ah only gives you 50Ah usable (50% DoD) before you start destroying it. LiFePO4 gives you 80Ah from the same nominal capacity. DoD directly determines how many batteries you need—ignoring it leads to undersized systems that kill batteries early.

LiFePO4 vs. lead-acid: is the premium worth it?

Almost always yes for anything beyond a weekend cabin. LiFePO4 costs 2–3× more upfront but delivers 6× the cycle life, 60% more usable capacity per battery, and 95% round-trip efficiency vs. 80%. Over the system’s lifetime, the cost per kWh delivered is usually lower.