Hydrogen

[Bruce53]

My Mercruiser sterndrive shop manual is wildly concerned with battery charging and hydrogen. They keep emphasizing the danger of explosions. They even say to remove the caps when charging. In all modern batteries, the caps allow the oxygen from the negative terminals to mix with the hydrogen from the positive terminals (I think I have that right) producing pure water which drips back into the cells. Why on earth would they make that kind of error? Or... am I all messed up?
Many thanks...

 

[Bruce53]

Re: Hydrogen

I should have said: positive "plates" and negative plates. The battery has only one positive "terminal" and one negative terminal.
Sorry...

 

[JeffreyC]

Re: Hydrogen

My Mercruiser sterndrive shop manual is wildly concerned with battery charging and hydrogen. They keep emphasizing the danger of explosions. They even say to remove the caps when charging. In all modern batteries, the caps allow the oxygen from the negative terminals to mix with the hydrogen from the positive terminals (I think I have that right) producing pure water which drips back into the cells. Why on earth would they make that kind of error? Or... am I all messed up?
Many thanks...

The reason they tell you to pop the tops on the battery is simple, when you are charging a battery especially for the first time like say a Motorcycle battery, it can produce more pressure inside the unit than it can disperse. Like blowing up a balloon with an air compressor, if you will. The more amperage you apply the more pressure you will have inside the battery, and yes I have seen more than one pop, not pretty. I am not an expert on batteries, can't even tell you what liquids are inside them to tell you the truth, but I am a mechanic and have restored cars for over 25 years, and if Hydrogen is one of the elements, BE CAREFUL. I also have a lot of experience with hydrogen, let me tell you, VERY explosive! Hydrogen is lighter than air however and with the tops off the battery, it will dissipate very quickly, but can get trapped under things and sit, just waiting for that spark, make sure your battery is in an open area when charging. Also to get the best result, put your charger on the lowest amperage possible and allow it to charge for at least 4 hours, trickle charge beats rapid charge every time. Sorry so long winded, but hope this helps.

 

[sschefer]

Re: Hydrogen

Funny, I was at Interstate the other day getting a couple of Optima's and overheard the guy at the store tell a customer something I thought made a lot of sense. He said all the batteries have been charged fully and tested however, you should buy a pair of 18" cables and connect them to the battery and then your charger to the cables. The idea is to keep any sparks that might occur from being near enough to the battery to cause the hydrogen gas that might be trapped in the area to explode. He also said since the battery had been fully charged there was no need to remove the vented caps when charging.

 

[rschap1]

Re: Hydrogen

It happens
I had an Interstate (not slamming them, guessing it could have been ANY brand etc.)explode last winter.
I had eight different batteries (boat, jet ski, deep cell for shorestation) all on a cart in my garage.
I had 3 tiny float chargers that I circulated amongst the batteries during the winter.
The interstate that blew up was not even charging when this happened.
The cart was under a shelf about 3 feet above the battery tops.
I opened the garage door and took a step inside just in time to hear BOOM !!
It took a minute to see what actually happened.
But it looks like the shelf help a build up of hydrogen (remember the Hindenburg?) and the door opener, even though a shrot distance away and at a higher height sparked and the two were able to hook up.
I do not think that it actually takes a huge amount of compressed gas to blow up.
I think if even "free" hydrogen gets sparked and it leads back to a compressed mass it can go up.
??
I am no expert, scientist, etc. BUT I am A LOT more careful around lead acid batteries now.
Luckily I didn't have anything more than a BIG mess to clean up but after seeing and hearing it happen I will tell you to USE CAUTION ! ! !

Run those bilge blowers, fuel fumes, and battery gases

 

[dingbat]

Re: Hydrogen

In all modern batteries, the caps allow the oxygen from the negative terminals to mix with the hydrogen from the positive terminals (I think I have that right) producing pure water which drips back into the cells.

It takes two molecules of the diatomic hydrogen gas, combined with one molecule of the diatomic oxygen gas to produce two molecules of water. The formation of water from it's elements produces, in addition to water, a tremendous amount of energy, 572 kJ to be exact. You are probably familiar with this reaction from the spaceshuttle Challenger disaster.

So much for the magical water making battery caps.