Home - Blog - 2019-10-11

Removing a Stylus Battery

(Click on any picture to see a full-size version.)

The Problem

My laptop is an HP Elitebook Revolve 810.
It has a touchscreen and a battery-powered stylus.

black stylus with one button
(HP Executive Tablet Pen R2, P/N 745123-001)

Today the stylus did not work.

I unscrewed the stylus to test the AAA battery.

stylus unscrewed in half

The battery would not slide out.

A multimeter confirmed that the battery was dead.
I assumed it leaked and corroded to the terminal.

multimeter reading 1.00 volts on stuck battery

I fretted about how to remove the battery.
I could not push it out from 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.

HP's support page had nothing helpful.
The only suggestion I found online was to fling it out.

The Solution

I decided to try to dissolve the leaked crud
to free the battery from the terminal.

I poured 70% isoprolyl alcohol into the stylus,
capped the end with my thumb, and shook it.

Doing this for about ten seconds freed the battery.

swollen, leaky aaa battery

The battery had swelled and leaked into the stylus.

The Mistake

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.
It no longer touches both ends when screwed together.

A small magnet on the end of the battery
makes it long enough to reach both terminals.

a 5mm magnet on the positive end of the battery

This will have to be a permanent hack.
A memento of this misadventure.

The Cause

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).

stylus tip on a multimeter

I carry the stylus in a pencil bag in my backpack.
This 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 or NiMH batteries that will not leak,
or by making a shroud to go over the tip.

The Conclusion

More alcohol and shaking cleaned the stylus.
(50% isoproyl seemed to work faster than 70%.)

The stylus works fine with a new battery installed.

stylus tip, magnet, battery, and cap

If there is anyone else out there
with a battery stuck in their HP stylus,
I hope this post about my experience helps.