RAK7289V2 reboots every ~8-10 minutes on 12V DC battery, stable on PoE

LPWAN Industrial Gateways / Concentrators
1

Hardware: RAK7289V2
Firmware: ChirpStack Gateway OS 4.11.0 (ramips/mt76x8)
Role: Field relay gateway (border_gateway: false), Gateway Mesh 4.1.3

Problem:
Gateway reboots cleanly every ~8-10 minutes when powered from 12V DC battery. Identical device on PoE/240V is completely stable. Tried two different fully charged 12V 7Ah SLA batteries — same result.

What we’ve ruled out:

  • Power quality — Schottky diode removed, direct battery connection, 5A fuse, 12.8V confirmed
  • OOM — memory consistently ~50MB free at death
  • CPU/load — healthy (0.2-0.4 load average)
  • Disk — overlay 6% used
  • Custom watchdog script — /overlay/watchdog.sh is logging only, never touches /dev/watchdog
  • Kernel panic/crash — no evidence in any log
  • Software crash — messages.old shows clean normal operation right up to the moment of death, mid-packet-relay, no final error

Key observation:
Death is completely silent. No log entry, no kernel message, no watchdog trigger message. The device simply stops and reboots. procd feeds /dev/watchdog directly. /sys/class/watchdog/watchdog0/timeout and timeleft are not accessible on this platform.

Question:
Is there a known difference in how the RAK7289V2 handles 12V DC input vs PoE-derived power that could cause the internal hardware watchdog to fire? Or is there a known issue with ChirpStack Gateway OS 4.11.0 on this hardware under battery power?