I have a backup sump pump, a 12V "Basement Watchdog".
However, immediately after installing it, I found the battery was basically dead.
Not wanting to buy a very expensive replacement battery, I got a Deep Cycle Marine battery, which works beautifully.
I've been told that the "Basement Watchdog" battery is specially designed to be safe to use indoors, as it is sealed, while my Marine battery "emits dangerous fumes".
The sump pit is in my basement, in a crawl space.
While there is certainly a lack of ventilation, it does have an hvac register (which doesn't prevent the crawl space from smelling like standing ground water when there are a few inches in the pit).
There's no warnings on the battery regarding indoor use.
I thought the battery only released said "dangerous fumes" when rapidly charged, and mine is charged via a very low current charger.
Is it safe to use this battery?
Best Answer
3% hydrogen to air is explosive. Even sealed batteries discharge some hydrogen gas when charged--they have to release the pressure or they will break the case. The seal is accomplished with a rubber (or silicone like material) over the port and usually a plastic shield welded in place to keep the seals in place. These batteries are not designed to be refilled.
The risk of explosion is very low with both battery types unless overcharged. Open cell or vented batteries require a flame arrestor (see NEC 480.11). In some systems this is as simple as a strip of mesh fabric like red scotch bright secured over the cells it needs to be acid resistant because a large component of batteries is sulfuric acid.
With the flame arrestor in place both batteries present similar hazards with the exception that marine deep cycle batteries many times end up being larger (more amp hours) so they take longer to become over charged, so there is really no difference in hazard after a flame arrestor is installed.