How to remove a stuck battery cap from a Mag-Lite?

September 1, 2008 7:16 PM

The battery cap on my Mag-Lite is stuck. Any ideas as to how to remove it?

I tried using bare hands, rubber gloves for extra traction, sticking the damn thing in a vise and repeating but I cannot get the cap off. It will not twist one iota. It stripped some of the rubber off my vise.

I also tried spraying the point of contact between the cap and barrel with WD-40 and later tried lubricating it with oil. No luck.

Right now I have it wrapped in a condom and sitting in a bucket of ice. The idea is to get it to contract some, but maybe I haven't thought my cunning plan all the way through.

Any other ideas as to how I might be able to get the cap off?

posted by Ziggy Zaga to home & garden (9 comments total)

two pairs of slip-joint pliers (more commonly known where I am from as Channel Locks). grip the body with one pair and twist the endcap with the other.
posted by namewithoutwords at 7:26 PM on September 1, 2008

If the cap is cross-threaded (not uncommon with maglights), then hitting the bottom with a mallet could help....
posted by JMOZ at 8:02 PM on September 1, 2008

Yes, that or a bench-mounted vise with metal jaws and channel locks. Soak with Liquid Wrench overnight.

What you're doing with the ice is getting it more stuck by contracting the cap and the body of the flashlight. If you could cool the cap apart from the body, this would have a chance. Since you can't, I think it would be better to apply heat to the body around the cap and expand the body away from the cap. Kind of works opposite from your typical nut and bolt.

Go to your friendly neighborhood auto mechanic and for five bucks he/she will fix you up.
posted by luckypozzo at 8:05 PM on September 1, 2008

Seconding luckypozzo. There's a classic engineering puzzle about chilling a joint that's exactly what you have going on: when things contract, -so does the gap between them-. You want heat, not cold, in this situation.

You could try a fabric strap wrench of the type used to remove oil filters if you don't want to mar the Maglite, but other than that variation you simply have to force the thing off with whatever you have to hand.
posted by jet_silver at 8:47 PM on September 1, 2008

Run it under hot water, and then rap it sharply a few times with the handle of a screwdriver. Then try untwisting it, using two pairs of pliers if need be.

If that doesn't work, buy a new one. (They aren't that expensive.)
posted by Class Goat at 8:55 PM on September 1, 2008

If it's not cross-threaded it may be galled, in which case you may get it apart but it'll be ruined.

Aluminum is notorious for galling but it's easy enough to lubricate it.

Super-lube is good because it won't damage the o-rings.
posted by Confess, Fletch at 10:42 PM on September 1, 2008

Mag lites have lifetime warranties. If it's not one of those $10 AA models you could just send it for service.
posted by Mitheral at 11:10 PM on September 1, 2008

Is it possible the batteries inside have leaked? If so, I think you're not going be able to get the cap off without ruining the whole thing.
posted by IvyMike at 12:09 AM on September 2, 2008

I've had this problem, the batteries leaked. I got it open but I also squeezed it too tight that the batteries wouldn't come out!
posted by jara1953 at 3:45 AM on September 2, 2008