Overfilling batteries

[wchevron]

i have a deka marine master dc31 house battery. i checked the fluid levels & noticed it was down about an 1". i added distilled water to each section and filled it to about 1/4"-1/2" to the top. yesterday morning i noticed a dried puddle under the battery. i had spilt some water filling the battery and figured it was from that. last night i noticed there was a smaller dried spot in the new location i had put the battery. then i noticed a small opening on the top side of the battery with a drop of water on it. i rocked the battery back and forth and noticed a couple of drops come out. this morning, there was a smaller area of water under the battery so whatever is coming out is lessening. could i have overfilled the battery? by refilling it, when the new water mixes with the existing acid, does it expand?

[raisin56]

Its not the mixing per say that changes the level its the charge/discharge that causes level change. Add rocking and rolling of the boat and that's why you want to be sure to have them in a battery box.

Dan

[SteveInMD]

There are usually plastic tabs that protrude down into the battery where you fill it. You are suppose to fill the battery so the liquid just touches the tabs. I'm not sure if your battery has these or not, but most do.

The the water does not expand when it hits the acid. However, when the battery is charging it does create some hydrogen gas. Gas bubbles form in the battery, which cause the liquid level to rise. That's why you are not suppose to fill it to the top.

You might also check your charging voltage. Charging at a voltage that's too high will cause more hydrogen gas to form than is necessary which can "boil" the liquid from the battery.

[wchevron]

the batteries are in my basement so there is no rocking. i haven't hooked them up to the charger since i filled them up. steve, my starter battery has those tabs. this battery has screw caps that don't protrude at all so i'm still a 1/4" to 1/2" below the bottom of the caps.

[Rockter]

WC...

In warmer weather, on motorcycles, the acid tends to drip out of the battery breather if the battery is too full. It attacks metal like crazy and feasts on chrome fittings.

Charging the battery warms it up too, and has the same tendancy to drip.

You could get a wee pipette, and decant some of it out of there, out of each cell. I try to fill the batery until there is about 1/4" fluid above the battery plates. It means that I have got to check them more often, but it doesn't drip out.