Werk #18762: ups_capacity: Fix crash on negative remaining battery time

Component	Checks & agents
Title	ups_capacity: Fix crash on negative remaining battery time
Date	Aug 18, 2026
Level	Trivial Change
Class	Bug Fix
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	3.0.0b1 Not yet released Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT 2.5.0p13 Not yet released Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT 2.4.0p36 Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

This affects users monitoring UPS devices via SNMP whose device reports a negative value for the remaining battery time (upsEstimatedMinutesRemaining, OID .1.3.6.1.2.1.33.1.2.3.0). While that value is specified as non-negative, some devices report a negative value when they cannot determine the remaining time.

Previously the Battery capacity service crashed in this case with:

File ".../cmk/agent_based/v1/render.py", line 76, in _gen_timespan_chunks
    raise ValueError("Cannot render negative timespan")

The service now goes UNKNOWN and reports the invalid value instead of crashing, for example:

Device reported an invalid remaining battery time (-60 seconds)

No battery_seconds_remaining metric is reported in this case. The battery charge level and the time running on battery are not affected and are still reported as before.

To the list of all Werks