Ever wanted to know how much power your HP iPAQ hx4700's wireless units consume?

Upon request (please also see the just-linked article for a more thorough elaboration on the background of all this and how the current screenshots should be interpreted), I’ve made some power consumption tests on the HP iPAQ hx4700 regarding the wireless units.

First, the Bluetooth (BT) unit. Please see the following screenshot taken with acbPowerMeter:

It shows three cases (note that these tests were all done with the disabled Navi service. Without disabling it, there were considerably more and much higher, transient peaks in the chart as can be seen in this shot):

1. BT unit off; ~102 mA
2. BT unit (and the blue LED) on (the first two peaks and the first half of the third; note that, in the third peak, I’ve also disabled the BT being discoverable. This had absolutely no effect on the power consumption); ~188 mA
3. BT unit on, blue LED off (the second half of the third peak); ~186 mA (as can be seen, the bright, blue LED consumes about 2 mA; see my disable-the-hx4700-LED posts in my blog on how the LED can be disabled).

What does this mean?

Unlike with ANY Pocket PC I’ve ever tested, the Bluetooth unit in the hx4700 consumes a LOT of power even when idling (and even with the BT LED/being discoverable disabled).

Please note that this is NOT a CPU usage issue – I’ve thoroughly tested whether this problem is caused by a badly written piece of code that would just “kick in” with considerable CPU usage. It is unlike the case with the Bluetooth Manager PAN bug of the Pocket Loox 720 I’ve described here.

That is, while you can safely keep the BT unit on all Window Mobile devices I’ve ever tested (in this respect), the hx4700 with the new, 2.01 WM5 ROM is an exception. Only enable the Bluetooth on the hx4700 when it’s absolutely necessary!

What about the Wi-Fi unit?

The Wi-Fi unit, as with all the other Pocket PC’s I’ve ever tested (please do read my previous articles on power consumption issues if you haven’t done so!), behaves as supposed to. If you enable it and it’s in the “searching for networks” state, then, the net power Amperage to power the Wi-Fi unit will be around 223 mA (the average Amperage the device takes being around 325 mA), which means the power consumption of the entire device will be around 3.2 times more than with the Wi-Fi unit disabled. This screenshot shows this case (the previous case with, later, the Wi-Fi unit enabled. Note that the peak shows the unit’s having found a wireless network).

What about the suspended state?

Note that when suspended, wireless units won’t consume any energy because suspending a non-Phone Edition device (like the hx700) also means suspending its Bluetooth unit – as opposed to the Phone Edition case, where suspended Phone Edition devices still have an actively ‘listening’ Bluetooth unit. This is why you don’t need to power on your Phone Edition Pocket PC when you want to use it as a, say, modem via Bluetooth.

Request

Could please anyone test the additional power consumption of the Bluetooth unit with the previous, 2.0 WM5 and the WM2003SE ROM versions? I’d really like to know whether this bug only affects the 2.01 ROM version of the hx4700. I think so – IIRC, I haven’t seen such bugs when I tested the WM5 2.0 ROM version upon testing the hx4700 for BT anomalies for my PL720 bug article.

hx4700 users with the 2.01 ROM version may also want to give it a try just to confirm the bug’s existence.

Just use acbPowerMeter to test the power consumption.

UPDATE (08/22/2006, 4:50PM CET):

In the meantime, the excellent guys over at the Pocket PC Thoughts forums have measured the power consumption of the Bluetooth unit on WM2003SE hx4700’s.

As it has turned out, the hx4700 behaves equally bad under WM2003SE too, meaning this clearly is a hardware-related problem and NOT that of the 2.01 WM5 upgrade.

This also means the HP / HTC engineers have ROYALLY messed up something in the Bluetooth unit. I’d like to point out again and again that I’ve never seen any WM2003SE+ device with so power-hungry Bluetooth units. (The Bluetooth unit in ALL the WM2003SE+ Pocket PC’s I’ve ever measured consume between one and three milliamps – the hx4700 consumes more than an order of magnitude more power.)

UPDATE (08/26/2006):

1. PPCT frontpage
2. In the meantime, I've continued publishing Bluetooth power consumption-related articles. For example, I've just published one on the HTC Wizard - today's most popular Pocket PC Phone Edition device. It's certainly worth checking out - as can clearly be seen, the HTC Wizard, as with almost all the other Pocket PC's, introduces almost no additional power consumption when its Bluetooth unit is active. Again, as opposed to the hx4700.
3. BrightHand forum member tanbam has previously published an article on generic power consumption issues of the hx4700; he has also measured exactly the same results as I under both WM2003SE and WM5. The article is definitely worth reading for his other remarks too. Note that it was written before I've published my series of filesys / NaviPoint-related articles and hacks; now, we know what the power peaks the article refers to as of unknown origin are caused by. The article is also discussed here at BrightHand.