November 24, 2020 | 23:15

Linux Smartphone Project - Part III

Today I will report a brief description of the battery and power management of Mobian on a Pinephone.

Reading the battery parameters from the console was already quite special. The usual way with upower was not successful and provided only zero values. Without ACPI the readout only worked with:

# cat /sys/class/power_supply/axp20x-battery/uevent

My first measurements: At idle with active mobile network, BT and WLAN and 50% display brightness the power consumption is about 2.5 to 3W. At 100% display brightness it jumps up to 3.5 to 4W each time without any apps in the background. From the desktop perspective this may not sound bad, but in fact it is.

To get a hands-on impression of the power management I made up the following challenge between my old Apple iPhone7 (current iOS 14.2) and the Pinephone with Mobian. At…

  • 50% Battery Status
  • 100% Display-Brightness
  • 100% Audio-Volume
  • all radios turned on
  • no apps running in the background

…I have taken the time it takes for a device to reach 40%. After exactly 16 minutes the Pinephone broke this limit, while the iPhone still lingered around 47%. The result was expected, but clearly shows how optimisation and a certain product maturity can affect a system.

Challenge

The WLAN/BT module with its RTL8723CS chip always needs the internal battery - even with external power supply. This is not explained in the very good Wiki1. But a quick look at the construction plans2 revealed the explanation: The module gets its energy directly from the battery, bypassing the X-Power AXP803.3

Power-Tree Pinephone

As I’m replacing the battery of my 6 year old Macbook Pro tomorrow (the blog post on this will follow soon), it reminds me very much of a similar Apple design decision. A Macbook slows down so much when the battery is disconnected that working is hardly possible.

What definitely saves battery power and is a feature for me is the possibility to operate a Pinephone with relatively few connections. Except the connections to my Nextcloud (in the screenshot the host with 130.180…) no further connections to foreign hosts are made. A prerequisite for this is the removal of geoclue if you can dispense with its geolocation services.

Verbindungen Pinephone

That' s all for today.
Stay healthy!

Tomas Jakobs


  1. https://wiki.pine64.org/wiki/PinePhone ↩︎

  2. https://files.pine64.org/doc/PinePhone/PinePhone%20v1.2b%20Released%20Schematic.pdf ↩︎

  3. http://files.pine64.org/doc/datasheet/pine64/AXP803_Datasheet_V1.0.pdf ↩︎

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