[ale] what the heck battery reading

[Pat Regan]

On Fri, 18 Feb 2011 14:44:29 -0500
Jim Kinney <jim.kinney at gmail.com> wrote:

> Don't recall details but I think there's a way to calibrate the
> battery monitoring app. It involves running down the battery a bit and
> recharging for a while and making calculations from that. Not finding
> how on a quick google search.

He shouldn't need to do any sort of calibrating.  The percentages he is
seeing are probably being calculated straight out of the data returned
by ACPI.  

wonko at zaphod:~$ cat /proc/acpi/battery/BAT0/info 
present:                 yes
design capacity:         5100 mAh
last full capacity:      4736 mAh
battery technology:      rechargeable
design voltage:          14400 mV
design capacity warning: 578 mAh
design capacity low:     338 mAh
cycle count:		  0
capacity granularity 1:  10 mAh
capacity granularity 2:  25 mAh
model number:            Primary
serial number:            
battery type:            NiMH
OEM info:                Hewlett-Packard

"Design capacity" is how much juice the manufacturer says the battery
should hold.  Time and recharge cycles decrease the maximum charge of
the battery.  "Last full capacity" will be the maximum charge the
battery is no able to hold.

This laptop's battery is down to about 93% capacity after about one
year of use.  ACPI battery reporting on this laptop isn't perfect.  It
never reports charge/discharge rate and apparently it thinks this
battery is NiMH, which is wrong.

If the "last full capacity" is changing between reboots the bios is
probably just dopey and trying to make you believe your battery is in
better shape than it actually is.

Pat