Battery Room Ventilation Calculator
Hydrogen dilution airflow for battery banks.
Enter your values
ⓘ Live results
Results
- Required ventilation
- 12.9 CFM
- With 25% safety factor
- 16.1 CFM
- Air changes provided
- 0.65
- Minimum 1 ACH
- 20 CFM
- Design airflow
- 20 CFM
Quick answer
Battery ventilation is based on hydrogen evolution during charging, sized to hold concentration under 1% by volume.
CFM = 0.0269 x cells x charge current (per IEEE)
How to use the Battery Room Ventilation Calculator
- 1Count the cells and take the maximum charge current from the charger nameplate.
- 2Compare the hydrogen-based figure with a 1 ACH minimum and use the larger.
- 3Place the exhaust point high — hydrogen collects at the ceiling.
Worked example
Using the values the calculator loads with:
Inputs
- Number of cells24
- Charge current20 A
- Room volume1200 cu ft
Results
- Required ventilation12.9 CFM
- With 25% safety factor16.1 CFM
- Air changes provided0.65
- Minimum 1 ACH20 CFM
- Design airflow20 CFM
Frequently asked questions
Do sealed AGM batteries need this?
Much less, but valve-regulated cells still vent under overcharge, so codes often still require ventilation.
What is the danger threshold?
Hydrogen is flammable at 4% in air; designs target 1% for a wide margin.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.