Smartphones are notorious for mediocre battery life; some have trouble making it through a single day without needing to be charged, and even good ones need to get plugged into the charger overnight to bring them back to life for the next day. If you read a guide on extending battery life, like this one from Verizon, one of their main recommendations is disabling GPS on your unit. I don’t like this, since I want to use my Android phone as a geography tool, and for the best accuracy you need to have GPS enabled and running when you need it. What’s more, I wasn’t really sure this was the case – handheld GPS units can get up to 20-25 hours of use from a single set of batteries, and I wasn’t convinced that the battery drain on a cellphone could be that much worse.
So I thought I’d run a few tests on my Droid X phone to see how quickly each of these parameters by themselves drains the stock 1550 mAh / 3.7V battery:
- Baseline (everything turned off, but phone still powered on)
- WiFi 3G
- Battery fully-charged (charge indicator showed “Full” for at least an hour)
- All non-essential programs shut off using a task killer program
- Battery state monitored using the Battery Graph app (which exports battery percent vs. time data in CSV format)
- GPS kept on using Tracker Booster software; this software uses < 0.1% CPU load, so it shouldn’t consume that much battery life by itself
Initial runs were done overnight for at least 10 hours, but I quickly found out that battery drain time was linear, i.e. it took about the same time to drop from 90% to 80% battery as it did for 30% to 20%. So subsequent runs were cut short.
|Parameter||Time for battery charge to drop 10% (min.)||Total battery life (hrs)||Comments|
|Baseline (all services turned off, phone still on)||-||-||After 12 hours, battery still read 100%|
|Screen only||100||16.7||50% brightness|
|Bluetooth only||-||-||Active connection with microphone/headpiece; battery still at 100% after 12 hours|
|WiFi/3G only||270||45||No talk or network activities|
|GPS and screen||42||7||No talk or network activities|
A real disappointment for me; under normal use conditions, having the GPS up and running continuously seems to be the biggest power hog on my Droid X, and that may well be true for other phones as well. Keep the screen on, a necessity if you want to view maps or save data, and you’ll be lucky to get 7 hours since you’ll also have the map/data application drawing power as well. So if I want to use my Android unit out in the field for prolonged periods of time, I’m going to have to figure out ways to extend the battery life somehow, or use alternate sources of power. Some suggestions on how to do that tomorrow.
A few last points:
- If your GPS wasn’t going to be acquiring positions anyway, disabling GPS won’t make your battery last any longer than it would have anyway. It’s only if it keeps GPS signal/position acquisition from turning on that you’ll save on battery life, but you’ll lose all the location-dependent services (maps, navigation, geotagging, position tracking, etc.)
- Rather annoyingly on my Droid X, if you disable GPS with a widget button, you also disable using wireless networks for fast but rough position determinations, and also turn off Assisted GPS (where cell tower stations provide info that improves GPS performance). If you use the widget to turn GPS back on, Assisted GPS and wireless network position acquisition do not get turned back on again; you have to go to Settings => Location & Security to turn those back on again. Your phone may be different – check and see.
- The Bluetooth results are encouraging; I’ll be testing a few apps in the future that let you use a Bluetooth GPS receiver with an Android phone, and this might be a good way to extend battery life substantially.