This battery post is moving.

Discussion in 'General Electronics Chat' started by foolios, Oct 13, 2016.

  1. foolios

    Thread Starter Senior Member

    Feb 4, 2009
    On this 12v marine deep cycle battery. I noticed that the post is wiggling. It doesn't seem to want to come completely out but I can move it up and down.
    Does that mean it's not making good contact for charging and discharging of it's power?
    Is it repairable?
    How does this post actually connect?

    IMG_5263.JPG IMG_5264.JPG
  2. BR-549

    Distinguished Member

    Sep 22, 2013
    Does it snug up if you turn it to the right?
  3. NCSailor


    Jun 15, 2013
    I believe you are calling the threaded terminal the post. It looks as if the real post is still stable and that the threaded terminal has just been pressed into the battery post.
    If the post is loose then connections inside the battery are likely damaged and I would say it is not repairable.

    If, as I suspect, it is just the terminal bolt that is loose. you could probably tighten it up by carefully peening the post around the terminal with a punch. The post is usually quite soft (mostly lead) so it should be possible to close up the recess for the terminal. You need to be careful to not apply so much force that you stress the post/battery interface. I would use some kind of anvil behind the post to reduce the lateral loading of the punch and keep the force to the minimum necessary to deform the post around the terminal.

    There is no doubt that the loose fit is affecting the contact resistance both charging and discharging. At higher loads (+ or -) it is likely that the connection will get hot and potentially create other problems.
    I have never seen a marine battery made like this. It is IMO a very poor design, but if you can get a clean, secure (movement free) contact, you should be able to salvage the battery.

  4. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    FWIW Having experienced similar difficulty myself I concur with @NCSailor

    Another 'trick' I've found useful is application of a liberal quantity of NH4Cl to the area (if possible,attempt to 'work' the flux into the loose joint) followed by heating of the bolt only via a large electric soldering gun or electric soldering iron until the the surrounding lead just begins to fuse...
    Caution! -- Avoidance of battery disruption (secondary to ignition of the H2+O2 mixture in the 'head-space' of the cells) requires that the heat source does not produce plasma (e.g. flame), sparks, etc...

    Additionally, please be advised that bare-minimal safe practice requires wearing of a visor over 'splash goggles' and ready access to running water...

    Best regards and good luck!
    Last edited: Oct 14, 2016
  5. foolios

    Thread Starter Senior Member

    Feb 4, 2009
    Thanks for all the information and safety concerns.
    I don't have skill using those tools or techniques so I will just return the battery or use it for deposit if it's out of warranty.
    I think it's really close to the one year mark.

    Thanks again for the replies.
    Hypatia's Protege likes this.
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    Do you know where it was bought? I had an easy return for a Walmart battery that was near 1-year. In fact, I wasn't the original purchaser, but Walmart went off the marking on the battery. Other dealers may offer the same courtesy.

  7. MrSoftware

    Active Member

    Oct 29, 2013
    Regarding fixing the terminal with heat yourself; if you've ever seen a lead acid battery with liquid electrolyte explode (or the aftermath), it's horrifying. Acid absolutely everywhere. It will give you a new respect for how dangerous a battery can be. If you try it, just do your homework on safety first.
    NCSailor and Hypatia's Protege like this.