battery_last_replaced sensors crash with "missing timezone information" on HA 2026.4+

[d-trattner]

Checklist

• I have restarted Home Assistant after the HACS or manual install.
• I have read the FAQ's.
• I have enabled debug logging for my installation.
• I have filled out the issue template to the best of my ability.
• This issue only contains 1 issue (if you have multiple issues, open one issue for each issue).
• This issue is not a duplicate issue of any previous issues..

Battery Notes Version

v3.4.3

Describe the issue

After updating to HA Core 2026.4, all sensor.*_battery_last_replaced entities
crash during setup with:

ValueError: Invalid datetime: sensor.XXX_battery_last_replaced provides state
'2024-08-31 13:27:15.201230', which is missing timezone information

Impact: The error causes the coordinator update to fail, which makes ALL
battery_notes entities unavailable — not just the _last_replaced sensors but
also _battery_plus, _battery_plus_low, and _battery_type entities.
Effectively, the entire integration is broken.

This happens because coordinator.py returns naive datetimes (without timezone)
from the last_replaced and last_reported property getters. HA Core 2026.4
strictly enforces timezone-aware datetimes for SensorDeviceClass.TIMESTAMP.

Important: This also happens after a complete clean reinstall of battery_notes
(remove integration + all entities via HACS, reinstall, re-add all devices).
The naive timestamps come from device_entry.created_at which is used as the
default for last_replaced in coordinator.py __init__.

Root Cause: In coordinator.py, the last_replaced property getter returns
a naive datetime via datetime.fromisoformat(str(entry[LAST_REPLACED])) when the
stored value has no timezone suffix. The setter stores device_entry.created_at
without ensuring timezone awareness. The store migration (_fix_datetime_string)
only fixes the colon/period issue from pre-3.3.2, not missing timezones.
Same issue affects last_reported.

Proposed Fix: A minimal helper ensuring UTC on all datetime reads and writes:

def _ensure_utc(dt_val):
    if dt_val.tzinfo is None:
        return dt_val.replace(tzinfo=datetime.timezone.utc)
    return dt_val

Applied in coordinator.py to last_replaced and last_reported getters/setters.
Tested locally — resolves the issue completely. I can submit a PR if desired.

Related: #4595 fixed set_battery_replaced action but not this init path.

Reproduction steps

1. Update to HA Core 2026.4+
2. Install battery_notes v3.4.3 via HACS
3. Add any device with a battery (or have existing devices)
4. Restart HA
5. Check Settings → System → Logs for "missing timezone information" errors
6. Observe that all sensor.*_battery_last_replaced entities are unavailable

System Health details

System Information

version	core-2026.4.2
installation_type	Home Assistant OS
dev	false
hassio	true
docker	true
container_arch	amd64
user	root
virtualenv	false
python_version	3.14.2
os_name	Linux
os_version	6.12.77-haos
arch	x86_64
timezone	Europe/Vienna
config_dir	/config

Home Assistant Community Store

GitHub API	ok
GitHub Content	ok
GitHub Web	ok
HACS Data	ok
GitHub API Calls Remaining	4989
Installed Version	2.0.5
Stage	running
Available Repositories	2938
Downloaded Repositories	75

Home Assistant Cloud

logged_in	true
subscription_expiration	22. September 2026 um 02:00
relayer_connected	true
relayer_region	eu-central-1
remote_enabled	true
remote_connected	true
alexa_enabled	false
google_enabled	true
cloud_ice_servers_enabled	true
remote_server	eu-central-1-13.ui.nabu.casa
certificate_status	ready
instance_id	8559d840d5474c2ab1a66243384b65b0
can_reach_cert_server	ok
can_reach_cloud_auth	ok
can_reach_cloud	ok

Home Assistant Supervisor

host_os	Home Assistant OS 17.2
update_channel	stable
supervisor_version	supervisor-2026.04.0
agent_version	1.8.1
docker_version	29.3.1
disk_total	125.3 GB
disk_used	26.6 GB
nameservers	10.0.0.101, 10.0.0.100
healthy	true
supported	true
host_connectivity	true
supervisor_connectivity	true
ntp_synchronized	true
virtualization	kvm
board	ova
supervisor_api	ok
version_api	ok
installed_addons	Advanced SSH & Web Terminal (23.0.6), ESPHome Device Builder (2026.3.3), File editor (6.0.0), PS5 MQTT (1.4.0), Mosquitto broker (6.5.2), Studio Code Server (6.0.1), Music Assistant (2.7.8), HA Vibecode Agent (2.10.40), Home Assistant Time Machine (2.3.1)

Dashboards

dashboards	15
resources	46
views	46
mode	storage

Network Configuration

adapters	lo (disabled), enp6s18 (enabled, default, auto), docker0 (disabled), hassio (disabled), veth0620562 (disabled), veth77a9a03 (disabled), vethefb9b7d (disabled), veth24fdb69 (disabled), veth4879bf5 (disabled), vethb0689c7 (disabled), veth7ed418a (disabled), veth6a64c71 (disabled), veth2be522f (disabled), veth6530e40 (disabled), veth2d64dc2 (disabled)
ipv4_addresses	lo (127.0.0.1/8), enp6s18 (10.0.0.116/24), docker0 (172.30.232.1/23), hassio (172.30.32.1/23), veth0620562 (), veth77a9a03 (), vethefb9b7d (), veth24fdb69 (), veth4879bf5 (), vethb0689c7 (), veth7ed418a (), veth6a64c71 (), veth2be522f (), veth6530e40 (), veth2d64dc2 ()
ipv6_addresses	lo (::1/128), enp6s18 (fe80::2eec:17a4:6014:e461/64), docker0 (fe80::c8bf:c5ff:feef:f71d/64), hassio (fd0c:ac1e:2100::1/48, fe80::8cde:eff:fe64:da4b/64), veth0620562 (fe80::60c6:6eff:fe7b:9ae3/64), veth77a9a03 (fe80::4043:6fff:fe23:664e/64), vethefb9b7d (fe80::2070:89ff:fe13:5044/64), veth24fdb69 (fe80::c830:e3ff:fe9c:b51f/64), veth4879bf5 (fe80::9475:43ff:fe27:f948/64), vethb0689c7 (fe80::6406:24ff:fec4:5d90/64), veth7ed418a (fe80::aca0:ff:fe60:1d6f/64), veth6a64c71 (fe80::cc2:98ff:fe6e:5b3d/64), veth2be522f (fe80::68ec:30ff:fef1:fbb4/64), veth6530e40 (fe80::906e:35ff:fe9a:c1b6/64), veth2d64dc2 (fe80::3cb9:8aff:feee:7763/64)
announce_addresses	10.0.0.116, fe80::2eec:17a4:6014:e461

Recorder

oldest_recorder_run	8. März 2026 um 14:16
current_recorder_run	15. April 2026 um 11:26
estimated_db_size	3209.72 MiB
database_engine	sqlite
database_version	3.49.2

Debug logs

2026-04-15 11:02:25.590 ERROR (MainThread) [homeassistant.components.sensor]
Error adding entity sensor.wasser_hobbyraum_battery_last_replaced for domain
sensor with platform battery_notes
Traceback (most recent call last):
  File ".../entity_platform.py", line 680, in _async_add_entities
    ...
  File ".../sensor/__init__.py", line 622, in state
    raise ValueError(...)
ValueError: Invalid datetime: sensor.wasser_hobbyraum_battery_last_replaced
provides state '2024-08-31 13:27:15.201230', which is missing timezone information

Diagnostics dump

Diagnostics download not available for this integration.

[d-trattner]

PR with fix: #4619