Pontoon Boat & Deck Boat Forum

Years ago, me and a couple of colleagues almost blew up a hotel room because we charged a couple 12 v batteries to quick. They degassed and filled the room with hydrogen and oxygen. Pretty scary...

Anyhow, I'm about to install a 12 v battery in a seat compartment for my trolling motor. Is it safe to charge the battery there or should I just take it out after each use?

I just realized that I really don't know the answer to this question.

At first I was going to say it would not be a problem, since every boat I have ever owned has had the starting battery in a seat compartment at the rear of the boat. And some have had trolling motor batteries stored in seat compartments. And the last few came with charging systems installed to keep the batteries charged.

But then I realized that just because it has been done this way does not make it safe.

So I will be interested in reading the answers to this question.

my starting battery is not enclosed... so, no issue either way....

my two trolling batteries are in a seat compartment. i too have thought about 'enclosed charging' issues..... so, what i do, is while charging, is prop the seat open, with one of the bumpers.... keeps it open about 6" or so.... i have thought about installing vents to the compartment, but the size needed to ventilate the area may weaken the structure of the seat.

but.... in this day, of sealed batteries.... is ventilation needed?? no idea.

My starting battery is under one of the rear seats and it was in a similar location on my previous pontoon. The area under most pontoon seats is not air tight, unless you've done some mods to that area, so it should not be an issue.
Do you have a winter type enclosure that covers that area? If not, I don't think you'll have a problem.
Talk to a local tech at a nearby marina as well if you are still concerned.

Hydrogen gas dissipates so fast through the tiniest of openings, there is really nothing to worry about.

I also highly doubt the blowing up the hotel room story. I take it there was never any explosion. The amount of gas dissipated by charging a battery is very small and would also dissipate very fast.

You don't have to believe the story, but we had quite a few deep cycle tractor (I think) batteries (the really big ones) in that room. We were collecting some shallow geophysical data for about a week which required some serious battery power. Anyway, we charged them too fast and when we woke up, there were several batteries that were swollen and popping/sizzling. A battery might not discharge much gas under normal circumstances, but when you completely evaporate one, they'll put off some gas. We had to spend over $1k to buy new batteries the next day. Lesson learned!

Did the gas vent out of the room? Probably. But you just need the right mixture of oxygen to hydrogen to cause an explosive hazard and it isn't as much as you would think. It was scary nonetheless! Especially when you had to carry this sizzling battery out of the hotel to the car to be disposed of...

Anyway, thanks for the replies. I'll go ahead and install like I had planned and just prop the seat when charging. You all have a happy new year!

Hydrogen gas was likely dissipating faster than the battery was generating it. In a boat there is exactly ZERO worry for any to build up.

Interestingly, the gasses expelled during charging are actually oxygen AND hydrogen in the PERFECT proportion to recombine explosively, when they hit a spark. It's because you're actually separating water molecules in the battery solution through electrolysis. I remember as a teen, hooking up a series of one-hole stoppers and surgical tubing to a car battery, and charging it. We let the bubbles rise through a bowl of water, and when they rose to the surface, where we were holding a match, it would go "pop, pop, pop" as each bubble rose.

SO, we theorized: Propane gas, rising through a metal screen, from our bunsen burner can be lit above the metal screen, and it doesn't burn below the screen. We quickly decided to try the same thing with our "battery gas".

The sound of the gas exploding, in the little metal garden shed we were working in, left our ears ringing for about an hour. Needless to say, hydrogen and oxygen combustion does not just stay "above the wire screen"! We were lucky not to have been covered with acid - the explosion DID crack the battery.

There are many cars that have the battery installed in the passenger compartment under the rear seat or in the trunk. If it really was an issue, they wouldn't be loacted in either places.

Igniting the gas escaping a battery through an open battery cap is not a real good safety test.