Low Battery

Turned on my work Palm Tungsten E this morning and got a critical "Battery Low" warning.
The battery level was at around 7% (after being at 88% last night). I couldn't back
anything up to the SD Card, because the Palm OS had disabled access to the Card to
preserve Battery power. Since the charger cable was at work, this was a problem.
Fortunately I didn't lose any data.

What caused this sudden drop in Battery power? It's possible that a button was being
pressed in the generic case overnight.

I’ve also noticed that from within ZLauncher the battery level is flaky, 88% one
minute, 95% the next. The battery life is definitely not as good as the Sony NX60.
On the Palm support site is says "If the battery drains to the point where your handheld does not operate, it stores your data safely for about five days". That's good to know.