How to Change CPU Speed on the Battery Mode
- 1). Click your "Start" menu and "Control Panel."
- 2). Click "Hardware and Sound" and "Power Options."
- 3). Click "Change plan settings" under the selected power plan on the right side of the window.
- 4). Click "Change advanced power settings" near the bottom of the window.
- 5). Expand "Processor power management" from the list of settings and expand "Maximum processor state."
- 6). Click "On battery" and write "100" as the value. Click "OK" and "Save changes," and exit all windows.
Source...