[8125, K-JAM, P4300, MDA Vario General] Menneisyys:
This is a continuation to my previous article on how much power the Bluetooth / infrared units in the HTC Wizard (a.k.a. imate K-Jam, T-Mobile MDA Vario, Qtek 9100, MDA Vario, XDA mini S, SPV M3000, VPA Compact II, Dopod 838) consume.

Now that I don’t really use my HTC Wizard (official i-mate AKU2 ROM version 2.16.9.1 WWE), I have time to run some really lengthy power consumption tests (with the Wizard being uninterruptedly suspended for even days) to properly measure the additional power consumption of the Bluetooth (including it being discoverable) and the infrared unit. Note that, during this, I’ve kept (I’ve just switched it off in the wireless manager) the GSM radio disabled to keep out the “random” factor of the measurements and also keep down the overall power consumption so that the results can be measured with more confidence.

Without the two wireless units,

the battery charge level of the device decreases about 2.5% a day, which means about (2.5% a day means 2.5/24% (0.1%) an hour. That is, in an hour, the Wizard consumes about 1250 (the Wizard has a 1250 mAh battery and) * 0.1 * (1/100) mWh – that is, 1250/1000 = 1.25 mWh.

Infrared

If you don’t disable the infrared auto-receive in Settings/Connections/Beam (by just unticking “Receive all incoming beams”), then, the additional battery level will decrease with about 1.5% a day (with the standard, 1250 mAh battery). This means about 18/24 = 0.75 mWh power consumption.

Note that with WM5 PPC Phone Edition devices like the HTC Wizard, the infrared unit is ALWAYS on when the device is suspended and is looking for other, discovering infrared devices (in passive mode). This is why it is promptly found by desktop Windows computers / notebooks having an infrared unit and this is why it's consuming power even when the unit is suspended.

Bluetooth

If you enable Bluetooth, including enabling being discoverable (!), the battery consumption doesn’t increase – at least not in a way properly measurable in a one and a one-and-a-half-day-long test phase.

Note that I’ve sometimes tested during the discoverable-enabled test whether the device is indeed visible to the outside world (other Bluetooth devices discovering their Bluetooth neighborhood). This was always the case.

But you…

Note that the Bluetooth figures are a bit different from my previous article. The reason for this is very simple: with the AKU2 ROM, the Wizard likes “sticking” with a previous battery consumption level and only displays the current level after a soft reset. I didn’t take this into account when I’ve told you the battery level of the Wizard decreased between 6 and 7 % a day with enabled Bluetooth (I’ve forgotten to reset before starting with the test – only after the test and reading the battery meter – and, therefore, the difference was bigger than with properly resetting the device before starting the test.)

Verdict

You can safely keep the Bluetooth always enabled – it consumes even less power than I’ve previously thought.

You may, however, want to disable auto infrared-receive. The infrared unit of the device, while, compared to the GSM radio, has a negligible power consumption, disabling it will still result in a device availability that is some (dozens of) minutes more than otherwise under normal (with enabled GSM radio) circumstances. If, for example, you don’t recharge your Wizard for three days (which is perfectly imaginable with a not power hungry device like the Wizard), then, the enabled infrared unit will cause a 4.5% more battery level depletion.

Future work

I’ll elaborate on the HTC Universal (a.k.a. i-mate JasJar, Qtek 9000, O2 XDA Exec, SPV M5000, MDA IV/Pro) in the same way. I’ll also try to test some other devices. Stay tuned :)