Boiling battery?

[Iceseeker]

I have an on-board 3 bank charger and I have been having a problem recently with one of the trolling motor batteries leaking fluid from the top. I have been replacing with distilled water but will need to add more in a month or so.

There are no performce issuees just that the one seems to boil over. The initial install was completed by the dealer when I purchased new 6 years ago and I have not changed any of the wiring.

Any ideas on preventing the leaking?

Iceseeker

[BobT]

Over-charging a battery is one way to boil it. This could happen if the charger doesn't automatically shut off when the battery is at full charge.

Another is to charge it using excessive voltage. This could happen if the charger is putting out more than about 14vdc.

I think another possibility would be if you had an internal short in the battery causing excessive current flow.

[Fredd]

You are sure that you are not overfilling the cells? They should not be filled above the bottom of the insert (an inch or so below the top). If the level is not the issue you could switch around two of the banks to see if the problem persists across the other battery/bank. If it does, you may have a bank that is over powered or not shutting down.

[Surface Tension]

Can you visually see or hear it boiling? Some batteries tend to gas more then others when being charged.

I have a battery that gases enough that I have residue on top the battery after a charge.

It has done that since new.

A battery on its way out can boil when charged.

[slipperybob]

6 years old battery? Time for a new one. Well put a multimeter and check the voltage of battery on standby and battery on a load.

Anyway it's amperage that will cause the battery to boil. For example if you're charging at 15 amp. The charger will have some distortion and float between 10 amp and 20 amp, so it will average 15 amp. During the charge cycle the battery will heat up and boil. It's better to charge the battery at a lower amperage like 5 amps. It reduces the amount of heat becuase it's charging at a slower rate.

The age of the battery, over time the lead plate sulfates and battery charge capacity is reduced. Charger probably thinks the battery needs charging still, even when battery has reached it's maximum charge capacity. Hence the battery boils over the top.