Can’t Change Critical Battery Level in Windows 7

So with the heavy rainstorms we’ve been getting these pass few days, I’ve been having quite a few brown outs. Everything’s fine though since my computers are all backed by UPSes. However I do noticed that my HTPC always seems to hibernate whenever these brown outs occur. I checked the battery and it was at 99-100%. So I went into the power settings and noticed that the critical battery level action was set to hibernate and the critical battery level was set to 98%. I tried changing it to 10%, but the setting would revert back to 98% immediately after trying to apply changes.

I did a search and found the following 2 threads:

• Can’t change critical battery level – possible bug?
• Cannot change Critical Battery level- stuck at 98%

I tried to do what a few suggested such as changing my group policy for reserve battery notification, changing my permissions settings for power schemes in the registry, and a few others, but they all failed to work. The only thing that worked was running the powercfg.exe tool.

powercfg.exe -setdcvalueindex 8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c e73a048d-bf27-4f12-9731-8b2076e8891f 9a66d8d7-4ff7-4ef9-b5a2-5a326ca2a469 20

The 2 things you need to change are 8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c (power scheme GUID) and 20 (what percentage to set it to). To locate your power scheme GUIDs, open registry editor (regedit.exe) and go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power\User\PowerSchemes. The keys (i.e. folders) underneath that location are your GUIDs. I believe the GUID above is for the High Performance power scheme.

Here’s the command to set the Balanced power scheme to have a critical battery level of 10%:
powercfg.exe -setdcvalueindex 381b4222-f694-41f0-9685-ff5bb260df2e e73a048d-bf27-4f12-9731-8b2076e8891f 9a66d8d7-4ff7-4ef9-b5a2-5a326ca2a469 10