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Root Battery Test Results w/CM7


Jan 4, 2012
So I recently switched from a root stock ROM on my NC to CM7 and thought I saw the battery discharge quicker. This led me to trying apps like Advance App Killer and Battery Defender to try and maximize my battery life and to do a little semi-scientific testing of how various settings affected things. First thing to note is that in all tests both "measured" time and % battery level were in integer increments of 1 minute and 1% respectively. With this type of resolution it is easy to get a 4% swing in discharge rate "data point" for what are essentially identical results. The screen brightness for all non-sleeping tests was set at ~10% and the browsing and video tests were conducted with the LAB501 Battery Life app. Things I looked at were the effect of the Max CPU setting and Advanced App Killer. Turns out that the default setting in CM7 is to turn off WiFi when the unit sleeps which obscures any impact Battery Defender might have. And now for the results.

- As suggested by Colchiro, Advanced App Killer actually increased the battery discharge rate. The incredible thing was that it increased the discharge rate by a factor of 100-200 times.
- The impact of increasing Max CPU from 800MHz (the clock speed of the stock ROM) to 1200MHz was in the noise level for browsing, video playback, and reading.
- Video playback had the same discharge rate whether WiFi was on or not
- When compared to the stock ROM, CM7 discharge rates for video playback and reading (both with WiFi off) were similar with CM7 maybe running 1-2% per hour higher at most. Browsing with CM7, however, was 4-6% per hour higher discharge rate than for the stock ROM.

- Avoid app killers like the plague or a hoard of zombies
- Battery saver apps are probably pointless if you already have the WiFi set to turn off when the unit goes to sleep
- Surprisingly increasing the max CPU speed does not appear to significantly affect battery life, at least the way I use my NC
- And finally, for some reason CM7 WiFi seems to run the battery down faster than the stock ROM. If anyone has any thoughts on why this might be so I would be interested in hearing them.
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