If you have the bq27x00_battery module loaded, it is included in kernel-power but not the stock kernel and I think it needs to be manually loaded (or added to /etc/modules) on older versions of kernel-power, but it loads automatically on the latest version. Then when you type the command "lshal | grep voltage.current" you get two results returned, one will be from the bq27x00_battery module (should be the second result, but I'm not sure it always will be) and this one will update when charging to give you the voltage in millivolts