BatteryBar 3.4.0 beta has been a disaster

[Chris]

It's definitely an issue with the installer. When it's upgrading, it tries to restart explorer so that it can replace BatteryBar without rebooting. In your case, the installer got hung up waiting for explorer to restart.

It still doesn't make sense why after the reboot the toolbar wouldn't show up. Does it show up in the toolbars menu? Perhaps it's just not turning on automatically but you can turn it on manually by right-clicking on the taskbar, going to Toolbars, and choosing BatteryBar.