Maybe best of both worlds. Leaving it a night in the freezer. And then holding it in your hand.
In bare hands is perhaps a bit too much, in that case I would suggest a pre-heated oven mitten.
Assuming that the alu on the outside will get warm faster than (the cold core of) the battery.
Tapping from time to time. On a piece of wood, if the battery does not protrude from the body.
is it a protected cell with a pcb on the negative side? if so solder something to the negative end, and pull on it, even if it s not protected, solder anyway, it’ll destroy the cell, most likely but it’ll be out
sadly the problem with that is by adding the WD you then create an airtight seal that`ll make a vacuum when trying to get the battery out, it`ll be nearly impossible.
I like the combo approach others have mentioned.
Freeze the thing overnight. Quick heat of the outside. Then smack it to break it loose.
If you can find something you can hit the light body without contacting the cell. Maybe the right size of plastic pipe?
Fits over body but not the head?
Short sharps taps might do it.
Some sort of thin penetrating oil. KA is right - Not WD-40, I suggest Deep Creep by Seafoam, Any auto parts store.
JB weld sticks like nothing else to metal. Ruff up the surface of a bolt face with some 80 or 100 grit. Battery end too.
Be sure the battery end is squeaky clean first.
Let it sit overnight. I put two bolt heads together like that. It held 120lbs.
Good luck
All the Best,
Jeff
Penetrating oil thinner the better - as last resort then the smacking around. There is some stuff called Kroil. It is even thinner and is less likely to form surface tension or vacuum.
If you go the JB route. be sure to use a Q-Tip or toothpick and put a little wax or grease on the sides of the light body and work a bit into the crack betewwn the battery and the light.
Get JB in there and divine intervention will be needed.
yes, on something similar and it was the worst move ever, I had to drill a hole into the tube behind the bar and use an airline to get it out.
it`s the same principal as the old bicycle pumps, a dried out seal won`t create much resistance, lube it up and it`ll be impossible to move if you block the air outlet.