$ cat /proc/acpi/battery/BAT0/info
present:                 yes
design capacity:         5144 mAh
last full capacity:      5144 mAh
battery technology:      rechargeable
design voltage:          10800 mV
design capacity warning: 200 mAh
design capacity low:     100 mAh
cycle count:              0
capacity granularity 1:  100 mAh
capacity granularity 2:  100 mAh
model number:            Primary
serial number:           49233 2011/02/25
battery type:            LIon
OEM info:                Hewlett-Packard

##</code><code>##

$ cat /proc/acpi/battery/*/* | grep capacity:
design capacity:         5144 mAh
last full capacity:      5144 mAh
remaining capacity:      5144 mAh
$
##</code><code>##

$ perl -MDP -e'while(<>){/^(.*)\s+capacity:\s*((\d+).*)/ and$i{$1}=[$2,$3]}print"$_: $i{$_}[0], "for keys%i;printf"%5.1f%%\n",100*$i{remaining}[1]/$i{design}[1]' /proc/acpi/battery/*/*
remaining: 5144 mAh, design: 5144 mAh, last full: 5144 mAh, 100.0%