the plates falls to the bottom of the battery, this will at some stage cause that battery cell to short out and cease to exist as a cell, this in effect causes the other cells to over charge, and as a result the water in the batteries is slowly ( at first ) gassed of, as the water level drops down the plates the gassing increases and increases until the battery gassing verses plate exposed goes into an exponentially catastrophic failure resulting in the boiling of the batteries, the only good thing about this type of failure is the knowledge that at least you used the batteries to there maximum. this failure can only be predicted by regular battery checks and you will notice 5 cells low on water and one not, it is important to scrap this battery in order to prevent boiling.
3)Poor maintenance of the batteries ie checking water level, permits the level to drop below the plated, this has the effect of reducing the voltage of each cell , and in effect causes the batteries to boil with a perfectly good charger
4)Iin the event of a charger failure the charger regulator could fail causing the full current of the charger to be pumped into the batteries causing a fast boiling in this case expect to see a battery voltage of 15 volts plus.
What do i look for and how do i stop
my batteries boiling ?
Boiling a battery is almost inevitable if you do not look regularly at your batteries to prevent them boiling, where as there is no doubt that the final act of actually boiling the battery only takes a few hours, the signs were there 4 weeks before, but you never bothered to check your batteries, therefore the first thing you knew was the nasty acid smell in the boat.
simple battery checks
1)check water level, expect to top up ( this is good and shows your batteries are performing well ), the water used varies from none ( low charge rate week end boat ) to
2)switch on charger, after 5 hrs plus remove all lids, ensure all cells are gassing, remove any battery with a cell not gassing, with 24 volt system replace both batteries and not just one.
3)if when topping up a 6 cell battery (
12 volts ) 5 cells take much more water than the sixth replace this battery .
4)if the batteries boil: if the voltage is less than 14 volts the batteries are the problem, 15 plus the charger is the problem.
Battery chargers in general:
most members of the public make the same mistake when buying marine battery chargers, they simply go into a chandlers and ask for a 50 amp charger, there may be a choice of two 50 amp charger, one at x pounds and one at y pounds with about 30% - 50 % cost difference between them, in most cases they go for the lower cost unit.
it is very important that you stop buying battery chargers based on amps as this a totally irrelevant figure, most people when they buy a 50 amp charger are under the illusion that they can then run 50 amps worth of kit from shore power, how wrong can you be, in order to run that 50 amps worth of equipment you would require a charger to give 50 amps at 12.6 volts = 630 watts output power. however if the charger is a standard transformer unit it may only give 50 amps at 4 volts and only at 16 amps at
12.6v = 200 watts, where as a constant current charger or switch mode power
