Pinebook Pro power and charging - Revision history

Dsimic: /* Charging indicator LED */ Expanded a bit

2023-11-08T22:28:04Z

Charging indicator LED: Expanded a bit

← Older revision		Revision as of 22:28, 8 November 2023
Line 19:		Line 19:
	# LED ''blinking with 0.5 Hz frequency'' signals some hardware error: typically [[#Battery temperature fix\|battery over-temperature protection]] or input under-voltage (from a [[:File:Pbp_charger_top.jpg\|failed charger]]); in this case the charger is also off, and the system is powered from the battery all the time.		# LED ''blinking with 0.5 Hz frequency'' signals some hardware error: typically [[#Battery temperature fix\|battery over-temperature protection]] or input under-voltage (from a [[:File:Pbp_charger_top.jpg\|failed charger]]); in this case the charger is also off, and the system is powered from the battery all the time.

	All other kinds of blinking really indicate the charger getting turned on and off, this happens when BQ24171 detects ''battery full'' condition, disables the charger, the system starts drawing current from the battery, the voltage quickly drops, and the charger is enabled again to compensate for the discharge. The blinking frequency would depend on the current system load, battery temperature, and the backlight level (as the backlight power source adds up to ~70 mV ripple to the voltage monitoring net). This "trickle-charging" is harmful for ~~Li-based~~ batteries, but no workaround is possible other than fully disconnecting the external power source, and it's not clear whether that would do more good than harm.		All other kinds of blinking really indicate the charger getting turned on and off, this happens when BQ24171 detects ''battery full'' condition, disables the charger, the system starts drawing current from the battery, the voltage quickly drops, and the charger is enabled again to compensate for the discharge. The blinking frequency would depend on the current system load, battery temperature, and the backlight level (as the backlight power source adds up to ~70 mV ripple to the voltage monitoring net). This "trickle-charging" is harmful for lithium batteries, but no workaround is possible other than fully disconnecting the external power source, and it's not clear whether that would do more good than harm.

			Another observed behavior is that the status LED blinks randomly, from time to time and unrelated to the system load, especially when the screen brightness is cranked to the maximum, and the battery isn't fully charged. This has been attributed to some strange feedback that the BQ24171 receives and becomes confused, but further analysis is required.

	=== Monitoring currents ===		=== Monitoring currents ===

Dsimic: /* Type-C current limit */ Clarified a bit

2023-11-08T14:50:10Z

Type-C current limit: Clarified a bit

← Older revision		Revision as of 14:50, 8 November 2023
Line 63:		Line 63:
	== Hardware modifications ==		== Hardware modifications ==
	=== Type-C current limit ===		=== Type-C current limit ===
	{{Warning\|The 0.5 A difference is there to carve out some power for a USB-C dock connected to the Pinebook Pro's USB-C port. It is against the PD specification, but it leaves some power to the USB-C dock, which it requires to power any devices connected to it. Thus, the procedure described in this section will most probably make using USB-C docks unreliable or even impossible.}}		{{Warning\|The 0.5 A difference described in this section is there to carve out some power for a USB-C dock connected to the Pinebook Pro's USB-C port. This is actually against the USB Power Delivery specification, but it leaves some power to the USB-C dock, which it requires to power itself and any devices connected to it. Thus, the procedure described in this section will most probably make using USB-C docks unreliable or even impossible, leaving the USB-C port usable for connecting only USB-C chargers or bus-powered USB-C devices.}}

	Since there's no software control over the input current limit unmodified PBP always tries to draw up to 2.5 A from a Type-C charger.		Since there's no software control over the input current limit unmodified PBP always tries to draw up to 2.5 A from a Type-C charger.

Dsimic: /* Battery temperature fix */ Added a warning

2023-11-08T14:43:27Z

Battery temperature fix: Added a warning

← Older revision		Revision as of 14:43, 8 November 2023
Line 74:		Line 74:

	=== Battery temperature fix ===		=== Battery temperature fix ===
			{{Warning\|The procedure described in this section alters the operating parameters of the lithium battery built into the Pinebokk Pro, which may be unsafe, and in extreme conditions may even introduce a fire hazard. Use the described procedure at your own risk. Additional verfication of the described procedure is currently pending.}}

	To ensure safe operation the charger IC is constantly monitoring the battery temperature with the sensor integrated inside the pack. The thermistor used is a 103AT NTC but the corresponding circuity on PBP mainboard was calculated for some other type. This results in the charger IC detecting 45 °C when the battery is in fact at just 35 °C, and 60 °C when the battery is at 46 °C. It's easy to hit this threshold with heavy CPU or GPU loads as the metal back cover heats up from the SoC and slightly warms up the battery. Under these conditions the charging is suspended (with charging LED signalling a hardware issue), and the intensive tasks are continued on battery power alone, heating it up even more.		To ensure safe operation the charger IC is constantly monitoring the battery temperature with the sensor integrated inside the pack. The thermistor used is a 103AT NTC but the corresponding circuity on PBP mainboard was calculated for some other type. This results in the charger IC detecting 45 °C when the battery is in fact at just 35 °C, and 60 °C when the battery is at 46 °C. It's easy to hit this threshold with heavy CPU or GPU loads as the metal back cover heats up from the SoC and slightly warms up the battery. Under these conditions the charging is suspended (with charging LED signalling a hardware issue), and the intensive tasks are continued on battery power alone, heating it up even more.

Dsimic: /* Type-C current limit */ Added a warning

2023-11-08T14:38:42Z

Type-C current limit: Added a warning

← Older revision		Revision as of 14:38, 8 November 2023
Line 63:		Line 63:
	== Hardware modifications ==		== Hardware modifications ==
	=== Type-C current limit ===		=== Type-C current limit ===
			{{Warning\|The 0.5 A difference is there to carve out some power for a USB-C dock connected to the Pinebook Pro's USB-C port. It is against the PD specification, but it leaves some power to the USB-C dock, which it requires to power any devices connected to it. Thus, the procedure described in this section will most probably make using USB-C docks unreliable or even impossible.}}

	Since there's no software control over the input current limit unmodified PBP always tries to draw up to 2.5 A from a Type-C charger.		Since there's no software control over the input current limit unmodified PBP always tries to draw up to 2.5 A from a Type-C charger.

Dsimic: /* Overview */ Fits better

2023-10-15T14:46:04Z

Overview: Fits better

← Older revision		Revision as of 14:46, 15 October 2023
Line 4:		Line 4:
	=== Overview ===		=== Overview ===

	No control of charging is possible other than by physically plugging and unplugging ~~the chargers~~.		No control of charging is possible other than by physically plugging and unplugging a charger.

	Software monitoring is also quite limited, one can check whether a charger is connected (in <code>/sys/class/power_supply/dc-charger/online</code> and <code>/sys/class/power_supply/tcpm-source-psy-4-0022/online</code>) and see the current battery voltage (in <code>/sys/class/power_supply/cw2015-battery/voltage_now</code>).		Software monitoring is also quite limited, one can check whether a charger is connected (in <code>/sys/class/power_supply/dc-charger/online</code> and <code>/sys/class/power_supply/tcpm-source-psy-4-0022/online</code>) and see the current battery voltage (in <code>/sys/class/power_supply/cw2015-battery/voltage_now</code>).

Fxc: Wiki style

2023-07-28T08:10:25Z

Wiki style

Show changes

Paulfertser: /* Charging indicator LED */ add a link to a failed PBP charger photo

2023-07-27T22:10:16Z

Charging indicator LED: add a link to a failed PBP charger photo

← Older revision		Revision as of 22:10, 27 July 2023
Line 32:		Line 32:
	# LED ''on'' means the charger is supplying current to the battery and the system;		# LED ''on'' means the charger is supplying current to the battery and the system;
	# LED ''off'' means the charger is turned off, and the whole system is powered from the battery;		# LED ''off'' means the charger is turned off, and the whole system is powered from the battery;
	# LED ''blinking with 0.5 Hz frequency'' signals some hardware error: typically [[#Battery temperature fix\|battery over-temperature protection]] or input under-voltage; in this case the charger is also off, and the system is powered from the battery all the time.		# LED ''blinking with 0.5 Hz frequency'' signals some hardware error: typically [[#Battery temperature fix\|battery over-temperature protection]] or input under-voltage (from a [[:File:Pbp_charger_top.jpg\|failed charger]]); in this case the charger is also off, and the system is powered from the battery all the time.

	All other kinds of blinking really indicate the charger getting turned		All other kinds of blinking really indicate the charger getting turned

Paulfertser: /* Type-C current limit */ mention that current higher than 2.5 A won't be reported in sysfs but still can be used

2023-07-03T08:23:38Z

Type-C current limit: mention that current higher than 2.5 A won't be reported in sysfs but still can be used

← Older revision		Revision as of 08:23, 3 July 2023
Line 138:		Line 138:
	overloaded, running out of specs.		overloaded, running out of specs.

	If all of the chargers you want to use can supply 3 A or more ''at 5 V'' consider lifting the limit to make it even with the		If all of the chargers you want to use can supply 3 A or more ''at 5 V'' (the sysfs file will still report 2.5 A so check the official charger specs and/or label) consider lifting the limit to make it even with the
	barrel plug charger. For that remove the ''R148'' resistor on the		barrel plug charger. For that remove the ''R148'' resistor on the
	[https://wiki.pine64.org/images/b/b7/Pinebookpro-v2.1-bottom-ref.pdf bottom layer] of the mainboard.		[https://wiki.pine64.org/images/b/b7/Pinebookpro-v2.1-bottom-ref.pdf bottom layer] of the mainboard.

Paulfertser: Initial version

2023-07-02T18:07:11Z

Initial version

New page

Pinebook Pro external power and charging circuity is quite
rudimentary, and hence quirky. This article aims to explain all the
fine points so that the behaviour could be understood and dealt with.

== Monitoring and control ==
=== Overview ===
No control of charging is possible other than by physically plugging
and unplugging the chargers.

Software monitoring is also quite limited, one can check whether a
charger is connected (in
<code>/sys/class/power_supply/dc-charger/online</code> and
<code>/sys/class/power_supply/tcpm-source-psy-4-0022/online</code>)
and see the current battery voltage (in
<code>/sys/class/power_supply/cw2015-battery/voltage_now</code>).

The [https://cdn.datasheetspdf.com/pdf-down/C/W/2/CW2015-Cellwise.pdf CW2015] battery monitoring IC only measures the voltage and tries to
guessimate the State Of Charge and Remaining Run Time. The last value
(along with the ''nominal'' battery capacity) is also used by the
kernel driver to ''compute'' the current. The estimations might be
relatively accurate under certain conditions but you can not really
know if they're met with your laptop load at any given moment, so the
only value provided that can be trusted is the voltage.

=== Charging indicator LED ===
There is a red LED near the barrel socket that's connected
directly to the
[https://www.ti.com/lit/ds/symlink/bq24171.pdf?ts=1607068456825&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ24171 BQ24171] battery charging IC.

It can indicate one of the three states:

# LED ''on'' means the charger is supplying current to the battery and the system;
# LED ''off'' means the charger is turned off, and the whole system is powered from the battery;
# LED ''blinking with 0.5 Hz frequency'' signals some hardware error: typically [[#Battery temperature fix|battery over-temperature protection]] or input under-voltage; in this case the charger is also off, and the system is powered from the battery all the time.

All other kinds of blinking really indicate the charger getting turned
on and off, this happens when BQ24171 detects ''battery full''
condition, disables the charger, the system starts drawing current
from the battery, the voltage quickly drops, and the charger is
enabled again to compensate for the discharge. The blinking frequency
would depend on the current system load, battery temperature, and the
backlight level (as the backlight power source adds up to ~70 mV
ripple to the voltage monitoring net). This "trickle-charging" is
harmful for Li-based batteries, but no workaround is possible other
than fully disconnecting the external power source, and it's not clear
whether that would do more good than harm.

=== Monitoring currents ===
The charging IC uses two measurement shunt resistors: ''R37'' for
input current, and ''R43'' for battery current, both
0.010 Ohm. They're easily accessible for external equipment after
removing the RF shield on the mainboard, and one can use a
battery-powered voltmeter or a differential probe to properly measure
the real current at any given moment. Do ''not'' connect non-isolated
oscilloscope ground clip to them, that might damage the
equipment.

With the external chargers disconnected the system is powered by the
battery, so measuring voltage on ''R43'' (along with the battery
voltage at about the same moment) can be used to learn the system
power consumption under different software loads.

== Charging ==
=== Overview ===
[[File:pbp-charging-simplified.png|thumb|Pinebook Pro simplified charging schematics]]
When an external charger is connected, the battery charging process is
automatically activated, it doesn't depend on any software
interactions and works all the same even with the main SoC powered
down. The system automatically chooses between the barrel socket
(limiting current draw to 3 A) and Type-C source (limited to
2.5 A), with the former preferred when both are connected at the
same time (but the current limit is enforced as if Type-C was used).

The maximum charging current under normal conditions is limited to
2.75 A and the voltage to 4.35 V. Battery temperature
affects these values, and if the measuring is [[#Battery temperature fix|done properly]] the charge is fully suspended under 0 °C or above
60 °C, maximum current halved below 10 °C, maximum voltage
reduced to 4.24 V above 45 °C and to 4.19 V above 50 °C.

The charging process automatically terminates when the voltage reaches
the recharge threshold (upper limit - 0.1 V) ''and'' the current
falls below 275 mA. However, this also stops supplying external
power to the system, so if it's running the battery voltage almost
immediately drops below the recharge threshold, and the charging is
turned on again.

=== Example run and charge time calculations ===

Assuming a fully charged 9600 mAh battery and an idle system
using ''performance'' cpufreq governor with backlight at 3700/4095
consuming 9.6 W we can expect

<code>9.6 Ah * 3.8 V / 9.6 W = 3.8 h</code>

so that gives 3.8 hours of run time.

If the same battery is empty and a barrel plug charger is
connected while system has the same load it will need

<code>9.6 Ah * 3.8 V / ((3 A * 5 V * 0.9 - 9.6 W) * 0.95) = 9.85 h</code>

that is 9.85 hours of charging from zero to full, assuming 0.9 DC-DC
conversion efficacy and 0.95 charging efficacy.

Removing the system load reduces the time to

<code>9.6 Ah * 3.8 V / (2.75 A * 3.8 V * 0.95) = 3.67 h</code>

so if you need to fully charge the battery, e.g. before a trip, the
fastest and most reliable way is to power down (not suspend) the system, leave the device with the charger connected
for a few hours, upside down for better cooling, and wait for the red
LED on the side to turn off.

=== Working without battery ===
With the battery disconnected the charger isn't going to turn on, and
the system won't be getting any power from the external source. That's
why PBP has additional bypass cable that allows connecting external
power directly to the system power bus. Of course it should be kept
disconnected when the battery is present to avoid excess voltage
overcharging and destroying the battery. It's also recommended to add
additional insulation to the cable connectors, as they expose battery
and charger positive terminals on bare metal, and should never be
accidentally connected to ground.

== Hardware modifications ==
=== Type-C current limit ===
Since there's no software control over the input current limit
unmodified PBP always tries to draw up to 2.5 A from a Type-C
charger.

It's recommended to manually check
<code>/sys/class/power_supply/tcpm-source-psy-4-0022/current_max</code>
for all the chargers you're using. When the value is lower than
2.5 A you shouldn't use that charger with PBP as it would get
overloaded, running out of specs.

If all of the chargers you want to use can supply 3 A or more ''at 5 V'' consider lifting the limit to make it even with the
barrel plug charger. For that remove the ''R148'' resistor on the
[https://wiki.pine64.org/images/b/b7/Pinebookpro-v2.1-bottom-ref.pdf bottom layer] of the mainboard.

The easiest way is to use a soldering iron tip big enough to hold a
1 mm drop of an SnPb solder (it mixes with Pb-free nicely and
lowers the melting point) to heat both sides of the resistor at once
and lift it off.

=== Battery temperature fix ===
To ensure safe operation the charger IC is constantly monitoring the
battery temperature with the sensor integrated inside the pack. The
thermistor used is a 103AT NTC but the corresponding circuity on PBP
mainboard was calculated for some other type. This results in the
charger IC detecting 45 °C when the battery is in
fact at just 35 °C, and 60 °C when the battery is at 46 °C. It's
easy to hit this threshold with heavy CPU or GPU loads as the metal
back cover heats up from the SoC and slightly warms up the battery. Under these conditions the charging is suspended (with charging
LED signalling a hardware issue), and the intensive tasks are
continued on battery power alone, heating it up even more.

To fix this issue the resistor divider needs to be replaced to match
the datasheet recommended values. For that one needs to change two
0402 resistors on the bottom side of the mainboard: use 2.2 kOhm
1 % for ''R52'' (instead of 4.4 kOhm installed by the factory),
note it's the one closer to the board edge; and 6.8 kOhm 1 % for ''R54''
(30 kOhm from the factory).

If your local hackspace doesn't have suitable resistors consider
getting a sample book from e.g. Aliexpress, it should cost less than
15 USD including shipping.