Thread: Is it possible to limit battery charge to say 80%?
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Old 04-23-2021, 01:03 PM   #5
j.p.s
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Posts: 5,806
Karma: 103362673
Join Date: Apr 2011
Device: pb360
Quote:
Originally Posted by atonement View Post
Also once fully charged and plugged in does the device take power from the mains or from the battery? I couldn't determine it.
Once the PMIC decides the battery is charged, the current to the battery stops and the kindle is powered from the charger. There are numerous inexpensive USB power meters that display voltage, current, and sometimes more. Some information is available from the kindle in /sys/class/power_supply/max*battery/

See more information below.

Quote:
Originally Posted by atonement View Post
In my rooted Android devices I have faithfully adhered to limiting charge between 30-80%. Probably that's why even after 4+ years in 2 of my oldest devices (2 & 3 years of intensive usage) battery health is still in the 85-90% range and they still deliver 8-10 hour SoT. Considering the difficulty in obtaining a replacement battery for Kindles in my country I would like to prolong the battery life as far as possible. After jailbreak I have no desire to get an Android based one.
Is this possible? Thanks.
I tried to do that a few years ago. It is easy enough to stop charging at some arbitrary percentage below 100, but that also stops powering the kindle from the charger and I
could not come up with a way to command powering the kindle from the charger without resuming charging. I also could not come up with a way to automatically resume charging while the kindle is sleeping.

I have a script to print battery status information. The following works on Voyage and PW3. For Oasis 2 or 3 change max77696-battery to max77796-battery
Code:
#!/bin/sh
DATE=`date '+%Y-%m-%dT%H:%M:%S'`
MA_NOW=`cat /sys/class/power_supply/max77696-battery/current_now`
V_NOW=`cat /sys/class/power_supply/max77696-battery/voltage_now`
MA_AV=`cat /sys/class/power_supply/max77696-battery/current_avg`
V_AV=`cat /sys/class/power_supply/max77696-battery/voltage_avg`
PCT=`cat /sys/class/power_supply/max77696-battery/capacity`
CHRG=`cat /sys/class/power_supply/max77696-battery/charge_now`
TBAT=`cat /sys/class/power_supply/max77696-battery/temp`
echo "$DATE $PCT $CHRG $MA_NOW $MA_AV $V_NOW $V_AV $TBAT"
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