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I was sitting in the hot tub and this crossed my mind: Do seal lead-acid batteries vent hydrogen when they charge/discharge?
 

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Sealed PbA can vent when you overcharge them. When sealed PbA vent it is bad news, as there is no way to replace the vented hydrogen gas; it is important that this gas is preserved for the battery's recombination process. Floodeds vent, and because of it, you must periodically water them. There is no way to water sealed batteries.
 

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I was sitting in the hot tub and this crossed my mind: Do seal lead-acid batteries vent hydrogen when they charge/discharge?
Just be clear, no, under normal conditions they do not vent. As Toecutter mentioned, it is possible though...if overcharged.
 
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All batteries are designed to vent in case of an overcharge in some way or another. They blow a cap or blow up. :)

Don't overcharge. Simple.
 

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I wanted to add that they can vent if over-discharged too. In a series string it is possible to reverse a single weak cell on discharge. It starts charging in backwards with the discharge current, and has little tolerance for that. It will quickly see high reverse voltages and start venting hydrogen.

They can also blow steam from discharging into a short circuit or near short circuit.
 

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Two words... Thermal runaway...

A sealed battery can have this happen just as easy and a pressure release or cap will open, venting the hydrogen, hopefully into a well ventilated area..

Thermal runaway is when a battery is charging and over heats lowing resistance and the battery sucks in more current, gets hotter, lower resistance, and the battery suck in more current......

Out door telco cabinets have blown up from this occurring. (Non venting cabinet in the winter... a little spark.....)



I was sitting in the hot tub and this crossed my mind: Do seal lead-acid batteries vent hydrogen when they charge/discharge?
 
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