default or selected kernelversion does not have config value CONFIG_BATTERY_Z2.
Result is shown for kernelversion 6.9.9

Z2 battery driver

modulename: z2_battery.ko

configname: CONFIG_BATTERY_Z2

Linux Kernel Configuration
└─>Device Drivers
└─>Power supply class support
└─>Z2 battery driver
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Say Y to include support for the battery on the Zipit Z2.

source code: