There are two ways to go about finding out battery status of a rooted Android phone. One is simple and uses cat, the other is android specific. Here is how the output of the first one looks like:

$ ./adb shell cat /sys/class/power_supply/battery/batt_attr_text
vref: 1248
batt_id: 4
batt_vol: 4155
batt_current: 229
batt_discharge_current: 0
batt_temperature: 391
Pd_M: 0
I_MBAT: 229
percent_last(RP): 99
percent_update: 90
level: 90
first_level: 15
full_level: 100
capacity: 1520
charging_source: USB
charging_enabled: Slow

That gives most of the battery information. If you just want to find out the current percentage, you can always do this:

$ ./adb shell cat /sys/class/power_supply/battery/batt_attr_text | grep ^level
level: 92

Another way is using the dumpsys utility, like so:

$ ./adb shell dumpsys battery
Current Battery Service state:
AC powered: false
USB powered: true
status: 2
health: 2
present: true
level: 92
scale: 100
temperature: 348
technology: Li-ion

This is a little bit more organized. Again, if you want to just see the percentage then grep is your friend:

$ ./adb shell dumpsys battery | grep level
level: 92