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Electric Vehicles

Hydrogen gas is generated as a natural byproduct of the lead-acid battery charging process. A four percent concentration of hydrogen gas is explosive and could cause severe injury or death. Charging must take place in an area that is adequately ventilated (minimum of five air exchanges per hour).

It is vital that a qualified consulting civil engineer licensed in the state where the facility is located examine the building plans.

The type, size, quantity, and location of ventilators to be used while charging of batteries is taking place must be determined. Hydrogen gas is a natural by-product of the charging process. Hydrogen is lighter than air and may accumulate and become trapped in ceiling cavities. Hydrogen is highly explosive and concentrations of only four percent are explosive.

The amount of hydrogen gas generated is dependent on many factors:

  1. The age of the battery pack
  2. The make and model of the battery pack
  3. The percentage of discharge of the battery pack
  4. The amount of electrolyte above the separators of each battery
  5. The type of charger
  6. The finish rate of the charger
  7. The ambient temperature

There are other factors that may affect the amount of hydrogen generated. The majority of gassing occurs in the last hours of the charge cycle and may double with a 25°F temperature rise or with a higher finishing rate of charge.

A significant amount of hydrogen is developed by each golf car and every effort must be made to prevent it from accumulating.

Five complete air exchanges per hour are considered suitable for ventilating an electric vehicle storage and charging area. The emphasis is on COMPLETE with no isolated pockets of gas remaining. Hydrogen detectors are available from safety equipment suppliers. There are other knowledgeable agencies that may recommend more or less air exchanges; be sure to check with local and state codes to confirm their requirements. As always, we suggest that you follow the most stringent code or recommendation.