Do lead acid batteries give off hydrogen gas when being discharged? Or only when they're being charged?

2 Answers

  • 4 months ago
    Favorite Answer

    Lead-acid (LA) batteries ....

    The discharge of a LA battery does not produce produce hydrogen gas. Whether hydrogen gas is produced during the charging of the LA battery depends on the type.

    For years cars have used "flooded" LA batteries where the water level must be maintained at intervals due to its conversion to H2 and O2 gases during the electrolysis which accompanied charging.

    With the advent of "sealed" and "maintenance free" LA batteries hydrogen ion (H+) is indirectly combined with O2 which may be produced during the charging cycle to generate water. Therefore, the water remains at a constant level, and doesn't require replenishment, hence, no "maintenance." Sealed LA batteries aren't really sealed. They have a valve or a plug which will release H2 and O2 gases if the batteries are overcharged.

  • 4 months ago

    When they are being charged.

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