Hydrogen Concentration Worksheet
During the recharge process, a lead acid battery releases hydrogen and oxygen through the electrolysis of sulfuric acid. The beginning of gassing is determined by the battery voltage. The amount of gas released depends on the current that is utilized in the electrolysis of the sulfuric acid. As the battery reaches its full state of charge, less current is used in converting lead sulfate from the negative and positive plates and more current is used in the gassing process.
4 Percent Concentraion
Four percent concentration of hydrogen is dangerous and can potentially explode. The National Fire Protection Association (NFPA) allows up to 1% concentration of hydrogen in a battery charging area. It is important to check with the local fire department for their local code. To keep the hydrogen concentration below 1%, adequate ventilation must be provided.
Rate Of Hydrogen Release:
1 amphere X 1 hour X 1 cell = 0.016 cubic feet of hydrogen / amphere hour / cell
Battery Hydrogen Calculation:
Rate of hydrogen concentration in cubic feet per hour is:
(battery amp hour rating) X (finish rate [in percent]) X (#of cells) X (0.016 cu.ft./ah/cell)
Rate Of Hydrogen Concentration:(battery amp hour rating) X (finish rate [in percent]) X (#of cells) X (0.016 cu.ft./ah/cell)
Example
Type Of Battery Used: 18-85F-29 (1190 Amp Hours) X (0.05 finish rate) X (18 cells) X (0.016 cu.ft./amp hours/cell) = 17.14 cu.ft./ battery X 15 batteries = |
Calculating Maximum Hydrogen ConcentrationLength X Width X Height = Cubic Feet
Example:
50 feet (Length) X 30 feet (Width) X 20 feet (Height) = 30,000 Cubic Feet X 0.01 (maximum allowable concentration) = |
Rate To Maximum Allowable Concentration:Maximum Hydrogen Concentration / Rate Of Hydrogen Concentration = Rate To Max Allowable Concentration
Example:
300 Cubic Feet / 257.1 cu.ft./hour = 1.17 hour or 70.01 minutes |
Rate Of Air Volume Removal:Room Volume / Rate To Maximum Allowable Concentration = Rate Of Air Volume Removal
Example:
30,000 cu.ft. / 70.01 minutes = 428.51 cu.ft./minute |