If I use grml zshrc v0.10.3 on Debian Wheezy (with 3.2.x Linux kernel), I get
the error message 

batterylinux:6: no such file or directory: /sys/class/power_supply/BAT0/capacity
                                       

before each prompt.There is no "capacity" file in /sys/class/power_supply/BAT0/
(which exists) but it is used unconditionally in line 1677 of etc/zsh/zshrc.

It worked fine with grml zshrc v0.7.3.