(…and making the stylus not drain future batteries)
My laptop is an HP Elitebook Revolve 810.
It has a touchscreen and a AAA-battery-powered stylus.
Today the stylus did not work.
I unscrewed the stylus to test the AAA battery.
The battery would not slide out.
A multimeter confirmed that the battery was dead.
I assumed it leaked and corroded to the terminal.
I fretted about how to remove the battery.
I could not push it out the other side.
Poking on the battery did not loosen it.
Magnets did not pull on it hard enough.
I could have drilled it out with a lathe,
but I didn't want to put holes in a battery.
I decided to try to dissolve the leaked crud
to free the battery from the terminal.
I poured 70% isopropyl alcohol into the stylus,
capped the end with my thumb, and shook it.
Doing this for about ten seconds freed the battery.
The battery had swelled and leaked into the stylus.
I put more alcohol and a new battery in the stylus
and shook it to clean out more corrosion.
I thought the battery would break crud free.
Instead it bent the terminal inside the stylus.
The battery no longer makes contact at both ends
when the stylus is screwed together.
A small magnet on the end of the battery
makes it long enough to reach both terminals.
This will have to be a permanent hack,
a memento of this little misadventure.
Why did the name-brand battery leak and die
after only a few months of occasional use?
It turns out that the tip of the stylus is a switch.
The stylus draws 5 milliamps for about 10 seconds
when the tip is pressed (and 100 microamps continuously).
I carry the stylus in a pencil bag in my backpack.
Whis puts it upright on the tip whenever I walk.
At 5mA for ten seconds every time it gets jostled,
it is no wonder the battery was completely drained.
This can be prevented from happening by
storing the stylus upside-down in the bag,
keeping the battery out of it when not in use,
using lithium of NiMH batteries that will not leak,
or by making a shroud to go over the tip.