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Battery Bank Amp Hour Calculator

Convert between amp-hours, kilowatt-hours and runtime for a battery bank.

About Battery Bank Amp Hour Calculator

Amp-hours only describe energy once multiplied by voltage. The C-rate matters because high discharge rates reduce effective capacity, especially in lead-acid chemistries. A battery rated at the 20-hour rate delivers noticeably less capacity when discharged in two hours, an effect described by Peukert’s law.

Formula

Battery Bank Amp Hour

kWh = Ah × V ÷ 1,000; runtime = usable kWh × 1,000 ÷ load watts

C-rate
Discharge current as a multiple of capacity, affecting available capacity

Worked example

With the default values below, Battery Bank Amp Hour Calculator returns Bank Energy of 19.2000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Bank capacityminimum 0 Ah
400 Ah
System voltageminimum 1 V
48 V
Loadminimum 1 W
1,000 W
Usable depth of dischargeaccepts 0–100 %
80 %

Results

Bank Energy
19.2000 kWh
Usable Energy
15.3600 kWh
Runtime at That Load
15.360 h
Load Current
20.833 A
Discharge C-Rate
0.0521 C

Step by step

  1. 1Values used
  2. 2Battery Bank Amp Hour
  3. 3Bank Energy= 19.2000 kWh
  4. 4Usable Energy= 15.3600 kWh
  5. 5Runtime at That Load= 15.360 h
  6. 6Load Current= 20.833 A
  7. 7Discharge C-Rate= 0.0521 C

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Battery Bank Amp Hour calculated?

kWh = Ah × V ÷ 1,000; runtime = usable kWh × 1,000 ÷ load watts Amp-hours only describe energy once multiplied by voltage. The C-rate matters because high discharge rates reduce effective capacity, especially in lead-acid chemistries.

Why does Battery Bank Amp Hour matter?

A battery rated at the 20-hour rate delivers noticeably less capacity when discharged in two hours, an effect described by Peukert’s law.

What values do I need to enter?

This calculator takes 4 inputs: Bank capacity, System voltage, Load, Usable depth of discharge. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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