Another big bonus delivered by the dock is a 4-cell 28 Whr battery to add to the tablet's 3-cell 42 Whr unit. Between the two, Lenovo rates Helix at 10 hours between charges. Our tests delivered less but still respectable time on battery considering that some of Lenovo's power-saving features were disabled. To test battery life, we played digital media files continuously with the screen brightness at 100 percent and all other energy saving features untouched. With both batteries fully charged, the first test of the laptop delivered six hours and 17 minutes. Recharging both batteries took 4:25. Then the tablet alone ran for 3:49 on its own battery and for another 2:22 after docking it. Total battery time that way was 6:11. Imagine how a Haswell-based system might perform.
Regrettably, the Helix lacks -- inside or out -- a charge status indicator; it's left solely to Windows. That means that the unit has to be opened and powered up to determine whether batteries are charging or charged. We consider this a major design flaw.