gas alarm goes of when charging

[mldpt]

Has any body had this problem, when my batteries are half discharged 300AH in total, and I connect a charger to them if left over night I get woken up by the gas alarm. I also have a 50 ah battery for the engine which has been connected to the charging systystem, when being charged, I switch off the alarm open all hatches fan by hand for about 20 minutes and it goes off, this only happens when the batteries are well down
I have just installed new batteries, and a new mains charger (sterling 30 A ) this does not happen when the engine is charging. I assume the batteries are gasing but I thought that was Hydrogen and if so is lighter than air so would rise out of the boat through ventilation I hope someboay can help.
Mike

 

[Oldhand]

I don't know if any battery produced gas will set off a gas alarm but you should not be trusting "natural ventilation" to disperse the hydrogen produced. You should either be using sealed batteries, batteries which have a vent port for an exhaust tube taken outside or have a semi sealed battery space which is vented from the top to the outside.

 

[mldpt]

I have never seen a boat with any special means of venting the batteries, sealed batteries are comparatively new so they are not the answer, most boats have their batteries under bunks etc so what happens totheir gas.
Mike

 

[[2574]]

Batteries on my boat are in an enclosed box which is then vented overboard via a 1 1/2 inch pipe.

rob

 

[Spicemariner]

Maybe youe engine start battery is being overcharged by the charger. Ours is only charged from the engine.

 

[Oldhand]

Sealed batteries have probably been around for 30 years, can't remeber when the first AC Delco "Freedom" battery appeared. Most boats do have "batteries under bunks etc" but I'll bet they are either sealed batteries, batteries with a vent tube or in a vented space on any reasonably modern boat. On my current boat all batteries have vent tubes which lead to an inverted "U" deck fitting except for the engine battery where the tube is taken to a locker space vent cowl. My last boat had totally sealed gel batteries (1990 vintage).

 

[mldpt]

thanks for that, I have isolated my starter battery, thinking that was the problem, but it did it again when charging just my domestic batteries.
Mike