Hi,
The Turtlebot dashboard displays battery info by parsing the contents of two files...
1) /proc/acpi/battery/BAT0/info
On my laptop, the contents of that file are... (note values may vary)
present: yes
design capacity: 4400 mAh
last full capacity: 4370 mAh
battery technology: rechargeable
design voltage: 11100 mV
design capacity warning: 215 mAh
design capacity low: 150 mAh
cycle count: 0
capacity granularity 1: 65 mAh
capacity granularity 2: 4155 mAh
model number: AS09A41
serial number: 2477
battery type: LION
OEM info: SONY Corp
2) /proc/acpi/battery/BAT0/state
present: yes
capacity state: ok
charging state: charged
present rate: 0 mA
remaining capacity: 4370 mAh
present voltage: 12493 mV
If either of these files do not exist, or your battery reports charge in a different way, you will run into issues (until this is fixed). You should check out this answer and see if it applies to you:
http://answers.ros.org/question/30631/turtlebot-unable-to-check-laptop-batterybat0state/