Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!oberon!sdcrdcf!hplabs!hp-pcd!hpcvlx!bill
From: bill@hpcvlx.HP.COM (Bill Frolik)
Newsgroups: comp.sys.hp
Subject: Re: Problem with HP 110
Message-ID: <1170004@hpcvlx.HP.COM>
Date: 5 Apr 88 17:44:50 GMT
References: <4257@cup.portal.com>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 24


> functions).  The problem started about a year ago when the battery
> would get down to about 70% and would warn of "low battery" and then
> shut off (as if the battery were completely gone).  As time went on,

Try replacing the battery; it probably just won't hold a charge.

The fuel gauge in the HP110 and Portable Plus doesn't actually measure
battery voltage or current -- it's controlled by a separate microprocessor
that monitors time and system configuration (Is recharger plugged in?
Is serial port turned on?  Is display turned on?  Is system running, or
asleep?  How about that modem?) and then looks up average subsystem current
drains in a ROM table.  Even though this scheme seems kind of kludgy,
it works fairly well if the battery is in good shape.  But if your battery
won't hold a charge, or if some part of the system is drawing an abnormally
large amount of current, the fuel gauge won't track along properly since
the only thing it measures is time.

The system also contains a circuit that watches for the low-battery condition
(voltage drops below a certain threshold) and generates an interrupt if it
ever occurs.  The system then issues the "low battery" warning and eventually
shuts off to prevent the battery from becoming too deeply discharged.

Bill Frolik / hplabs!hp-pcd!bill
Hewlett-Packard / Corvallis Workstation Operation / Corvallis, Oregon