What's the Drain Test?

The Battery Guru drain test is a method for checking your battery health, independently of the OS-supplied Health reading which Battery Guru for BlackBerry 10 displays in its Diagnostics page.

Performing the test will let you calculate the actual capacity of the battery in watt-hours. It may also cause the OS to recalibrate, resulting in an update of the Health reading.

Disclaimer: some people experience difficulty getting their device to charge and turn back on properly after fully draining the battery. By performing this test you are assuming responsibility for any and all risks associated with it, and Engenuity Corporation expressly disclaims liability for any problems that may arise during the execution of the procedure described herein, including but not limited to the destruction of your device or battery. Perform this test at your own risk.

Okay, How is it Done?

First make sure you have enough time to complete the test without interruption. Because battery characteristics are not "linear", a partial test will not give useful results. Usually just before you would normally put the phone in "bedside mode" or turn it off for the night is best. You'll need enough time to fully charge the battery if it's not already charged, then fully drain it. Afterwards you'll need to recharge it at least partially before you can use it again.

  1. Fully charge the battery: this means until the lightning bolt icon is gone from the battery indicator in the upper left of the home page, and Battery Guru shows a Level of 100% and a Power reading of 0.00W. (Note: in some devices, the level may read only 98% or 99% but this isn't a serious problem and may be corrected as a result of performing this operation.)
  2. Enable airplane mode: this stays off for the rest of the test, so you will not have network access until the test is done or you halt it.
  3. Set the Display brightness to the maximum setting. (Warning: this test is not designed to be used on a device with an AMOLED display, such as the Q10, so perform it at your own risk. AMOLED screens may be susceptible to "burn-in". In future we may provide support for a Q10 drain test.)
  4. Close all apps, except Battery Guru, which should be running during the test.
  5. Enable Keep Awake in Battery Guru's Diagnostics page, then return to the main page with the readings and graph.
  6. Remove the device from the charger and record the current time.
  7. Wait for the battery to drain. It will give the most accurate results if ambient light levels are consistent during the test. You can either place the device face-down (on a soft surface) so the light sensor sees little light (power will be about -0.5W and the test may take more than 10h) or face-up in a lighted area (power will be about -1.0W and the test may complete in under 6h).
  8. During the test, you may want to record the Power readings every hour or two. If the reading is stable during the test this may give a sufficiently accurate result. Alternatively, you can use the Export feature in the Records page to obtain a CSV file with all the data from the drain test, which will let you calculate a more accurate average power level.
  9. When the device has shut itself off from low battery, record the time again unless you plan to use the exported CSV data.
  10. Plug the device back into the charger and wait for it to restart, or restart it yourself after it's regained a useful charge. You may want to run Battery Guru again when the device reboots, so you can monitor the recharging.
  11. Remember to reset the Display brightness and turn off Airplane mode again.
  12. If you plan to use the exported data, go to Records and select the appropriate date/time range, then export to a CSV file and transfer this to a PC where you can load it into your spreadsheet software.

Using the Results

Having completed the drain test, you should have a start and end time and one or more recorded power values, or a CSV file. In either case, you will need to calculate the average power level over the entire period of draining (between the time you took it off the charger and the time it shut itself off), and the duration of the test in hours (e.g. 6.5 hours).

Multiply this average power level by the number of hours to give you the actual capacity of the battery in watt-hours (Wh).

To calculate Health, divide this value by the nominal value printed on the battery in your device and multiply by 100. The LS1 battery in the Z10 has a labelled capacity of 6.8Wh.

As an example, if your average power usage during the test was 0.97W, and the duration was 6.5h, the capacity is 6.305Wh (0.97 times 6.5). Dividing this by 6.8Wh gives 0.927 so the value for Health is 92.7%.

Congratulations, you've now verified the actual Health of your battery. Don't be surprised if it's a few percent different from the OS-supplied value displayed in Battery Guru: none of the measurements are accurate enough to expect more than being in the same general ballpark.

For some additional background, you may want to refer to the original CrackBerry post where this test was conceived for the PlayBook.