Hydrogen has no smell
Wikipedia’s hydrogen page is plain: the gas is colorless and odorless, and it burns. Flooded batteries release hydrogen while they charge, especially at the end of absorption and if the charger is too aggressive in heat. You will not “smell hydrogen.” 33 CFR 183.420 requires a vent system or other means so hydrogen can leave the boat. A sealed console with a wet cell on a charger is the opposite of that requirement.
Rotten eggs are a different molecule
The rotten-egg odor people notice at a battery box is hydrogen sulfide, not hydrogen. Wikipedia’s hydrogen-sulfide article is that smell. It can mean overcharge, a hot flooded pack, or contamination. It is a reason to stop charging, ventilate, and look at the charger program — not a reason to ignore the odorless hydrogen that may be there too.
No sparks in the box while it gasses
Jumping a gassing battery, dropping a wrench across posts, or switching a load in a closed well is an ignition story. We disconnect loads, ventilate, and treat the well as a place that may have gas after a charge. AGM still can vent under abuse; flooded always can.
Install details that matter
The federal battery section also keeps batteries away from sitting directly above or below a fuel tank or fuel filter, and requires that metallic objects cannot hit ungrounded terminals. Those are the same well we are asking to vent. We look at the whole box, not just the caps.
St. Petersburg and Tampa slips
Onboard chargers in closed engine rooms are this article. We come to the boat, open the space, and check whether a flooded pack has a path out. If it does not, the install is part of the quote with the battery.
AGM in the same well
If the starting battery is flooded and the house is AGM, the well still has to vent for the flooded pack. Sealed neighbors do not cancel the gas. We will not leave a new wet cell in a gasketed console that has no path out. That is the federal vent rule and the odorless-hydrogen fact together.
Sources
- Wikipedia — Hydrogen (odorless, flammable)
- Wikipedia — Hydrogen sulfide (rotten-egg odor)
- 33 CFR § 183.420 — Batteries (Cornell LII)
If this is the job on your boat, see how we replace batteries at the boat. We come to you — Florida towns and counties.