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Beta testing • Enabling RTC battery charging on Trixie makes RTC "disappear"

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Loaded the Sep5 nightly of Trixie on 2 Pi5 16G units. All was working great. Just received my RTC batteries for them and plugged them in. When I do:

Code:

 more /sys/devices/platform/soc@107c000000/soc@107c000000:rpi_rtc/rtc/rtc0/battery_voltage
I get 2764099
Charging shows 0
I then added

Code:

dtparam=rtc=bbat_vchg=3000000
to /boot/firmware/config.txt and rebooted.
the

Code:

 /sys/devices/platform/soc@107c000000/soc@107c000000:rpi_rtc 
is now gone sudo timedatectl shows:

Code:

  $ sudo timedatectl               Local time: Mon 2025-09-08 17:11:46 PDT           Universal time: Tue 2025-09-09 00:11:46 UTC                 RTC time: n/a                Time zone: America/Los_Angeles (PDT, -0700)System clock synchronized: yes              NTP service: active          RTC in local TZ: no 
Running

Code:

  $ sudo vcgencmd pmic_read_adc BATT_V      BATT_V volt(25)=2.76410000V  
So it still shows the battery volts, but it is not charging either.

removing the charging code line and running timedatectl shows:

Code:

$ sudo timedatectl               Local time: Mon 2025-09-08 17:18:55 PDT           Universal time: Tue 2025-09-09 00:18:55 UTC                 RTC time: Tue 2025-09-09 00:18:55                Time zone: America/Los_Angeles (PDT, -0700)System clock synchronized: yes              NTP service: active          RTC in local TZ: no

Code:

$ vcgencmd bootloader_version2025/08/27 20:01:47version 000d3ca289ae790a2e46225eb11b319c67642b1a (release)timestamp 1756321307update-time 1757117128capabilities 0x0000007f
Any ideas?

Statistics: Posted by 5ft24dave — Tue Sep 09, 2025 12:19 am



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