Skip to main content

Home  Mission  About Us  Service  Technical Information  Contact Information   
1. > 2. > 3. > 4. > 5. > 6. > 7. > 8. > 9. > 10. >  
Hydrogen Concentration Worksheet


During the recharging process, a lead battery releases hydrogen and oxygen through the electrolysis
of sulfuric acid. The beginning of gassing is determined by the battery voltage, but the amount of gas
depends on the current that isn't absorbed by the battery and is used in the electrolysis. As the battery
reaches its full state of charge, the acceptance of current becomes less and the liberation of hydrogen
is more.
Four percent (4%) concentration of hydrogen is dangerous and has a potential for an explosion.
Generally, the maximum allowable concentration of hydrogen is 1.50% of the room's cubic footage. To
keep the hydrogen concentration below 4%, adequate ventilation or proper air exchange of the room
must be provided.
 
Rate of Hydrogen Release
1 Ampere x 1 Hour x 1 Cell = 0.016 cubic feet / Ampere Hour / Cell
Battery Hydrogen Calculation
Ampere Hour x Finish Rate (percent) x Number of Cells x 0.016 Cubic Feet / Ampere Hour / Cell

Example:
Quantity = 20 Batteries
Type = 3DJ-200
Ampere Hour = 200 Ampere Hour
Battery Hydrogen Calculation
200 AH x 0.05 x 60 Cells x 0.016 Cubic Feet / Ampere Hour / Cell =
9.6 Cubic Feet / Hour / Battery x 20 Batteries = 192.0 Cubic Feet / Hour

Room Calculation
40' Long x 30' Wide x 15' High = 18,000 Cubic Feet
18,000 Cubic Feet x 0.015 (Maximum Allowable Concentration) = 270 Cubic Feet (Maximum)
Rate of Concentration Calculation
270 Cubic Feet (Maximum Allowable) ÷ 192.0 Cubic Feet / Hour = 1.4 Hours or 85 Minutes
Rate of Air Volume Removal
18,000 Cubic Feet ÷ 85 Minutes = 211.76 Cubic Feet / Minute
You will need at least one exchange of air per hour in the substation with the existing air conditioning system in order to NOT have a ventilation fan to exhaust battery gasses.