Forum Discussion

Finally_Time's avatar
Finally_Time
Explorer
Aug 05, 2016

Battery caps coming off.

For the third time, when I checked the battery water level for the chassis battery, I found the caps off the battery. (12 volt OEM battery; two caps, three cells under each) First time I thought I might not have snapped them down tight. Last time I double checked to make sure the caps were on tight. I didn’t have to add any water this time, but when replacing the caps, one snaps down but the other just kind of sits there. I can remove both by just lifting an edge by hand. For the house batteries I have to use a screwdriver to pry up an edge.
Do I have some kind of charging problem with off gassing blowing off the caps, defective caps, or should I just forget it and tape them down?
  • Finally_Time's avatar
    Finally_Time
    Explorer
    Aug 06, 2016
    Just went to the storage yard to take a real good look at that battery; even used my reading glasses this time. There is nothing on it to indicate it is a maintenance free battery, but that's not to say it isn't. Since this has been going on four months and 6,000 miles and everything is working ok, (it holds a charge, the engine starts, it doesn't need water), I just used some of the ever-useful duct tape to hold the caps over the cells. I left it loose enough so there is room to vent but the caps should stay over the cells to keep out any stuff that shouldn't be there.

    Thanks for the replies.
  • 2oldman's avatar
    2oldman
    Explorer II
    Aug 05, 2016
    mkirsch wrote:
    The caps on maintenance free batteries are designed to be installed once in the factory, and never removed by the end user.
    That would explain a lot.
  • mkirsch's avatar
    mkirsch
    Nomad II
    Aug 05, 2016
    If you are needing to add water to a maintenance free battery, that means you are overcharging it and boiling it dry. That also may explain why your caps keep popping off.

    The caps on maintenance free batteries are designed to be installed once in the factory, and never removed by the end user. They are not designed to be installed/removed repeatedly. It is likely you broke the mechanism that secured the caps the first time you popped them off to check the water.
  • JamesJudasPries's avatar
    JamesJudasPries
    Explorer
    Aug 05, 2016
    2oldman wrote:
    Is it possible road vibration is doing that? And in no case should the cap just 'sit there.'

    Can't say I've ever seen a 12v battery with just 2 caps.


    2 caps is common for motorcraft or other brands of flooded cranking batteries. Some even say 'maintenance free' and have those caps. seems they have a surplus of electrolyte to compensate for offgassing.
  • RJsfishin's avatar
    RJsfishin
    Explorer
    Aug 05, 2016
    If not fitting quite snuggly, probably just a gust of wind lifting it off.
    I'd never believe pressure is doing it,.....no way would the vents be completely blocked.

    2 OLD......I haven't seen a 12v battery in years w/ more than 2 caps.
  • 2oldman's avatar
    2oldman
    Explorer II
    Aug 05, 2016
    Is it possible road vibration is doing that? And in no case should the cap just 'sit there.'

    Can't say I've ever seen a 12v battery with just 2 caps.
  • westend's avatar
    westend
    Explorer
    Aug 05, 2016
    The cell cap cover should have a very positive latch or hold. It's possible that the electrolyte level is over-filled and the charging process is creating enough pressure to lift off a loose cover. They may sell replacement covers at an auto parts store. I've never had the need.
  • TakingThe5th's avatar
    TakingThe5th
    Explorer
    Aug 05, 2016
    Maybe it's as simple as the vents being blocked. The charging process creates pressure which must be released.

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