Supervolt SX-100P - unstable connection with updated bluetooth module

[abcklaus]

Checklist

• I have tried the latest version of BMS_BLE-HA.
• I have enabled debug logging for my installation.
• 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 issue.
• I have filled out the issue template to the best of my ability.

Provide the type of BMS you used:

Supervolt XS-100P / E&J BMS

Describe the issue

I am using two Supervolt batteries. Due to significant cell drift, one of the batteries was serviced by the manufacturer. The battery now has an improved balancer and a new Bluetooth module. Unfortunately, I have no further information about the updated Bluetooth module.

I am currently experiencing issues integrating the serviced battery into my Home Assistant installation.

For the Bluetooth connection, I am using an ESPHome Bluetooth Proxy. The distance between the proxy and the batteries is approximately 50 cm.

I tested the connection using the Supervolt app, and the connection remains stable for several minutes without any issues.

For all other tests, I ensured that the battery was no longer connected to the app.

After restarting the Homa Assistant installation or right after adding the battery to the integartion is is shown with all its values in the UI. After about 30 seconde the batterie disapears (unavailable).

Reproduction steps

Easiest way to reproduce the issue is a restart of Home Assistant server. The connection to the affected battery is working once. After that the battery disappears from the UI. The log shows:

2026-09-07 16:06:02.086 DEBUG (MainThread) [custom_components.bms_ble] Full error:
Traceback (most recent call last):
  File "/config/custom_components/bms_ble/coordinator.py", line 139, in _async_update_data
    if not (bms_data := await self._device.async_update()):
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.14/site-packages/aiobmsble/basebms.py", line 542, in async_update
    data: BMSSample = await self._async_update()
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.14/site-packages/aiobmsble/bms/ej_bms.py", line 211, in _async_update
    raw_data: Final[dict[int, bytes]] = await self._query_bms()
                                        ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.14/site-packages/aiobmsble/bms/ej_bms.py", line 199, in _query_bms
    await self._await_msg(cmd)
  File "/usr/local/lib/python3.14/site-packages/aiobmsble/basebms.py", line 475, in _await_msg
    raise TimeoutError
TimeoutError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/update_coordinator.py", line 435, in _async_refresh
    self.data = await self._async_update_data()
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/config/custom_components/bms_ble/coordinator.py", line 145, in _async_update_data
    raise UpdateFailed(
        translation_domain=DOMAIN, translation_key="bms_timeout"
    ) from err
homeassistant.helpers.update_coordinator.UpdateFailed: BMS communication timed out
2026-09-07 16:06:02.092 DEBUG (MainThread) [custom_components.bms_ble] Finished fetching libatt1EC8 data in 5.370 seconds (success: False)

Debug logs

I have attached a debug log of the BMS_BLE-HA intergartion

home-assistant_bms_ble_2026-09-07T14-06-18.851Z.log

[patman15]

Hi! Not sure this is a bug. It seems to work the first time and the second the BMS just not answers. How often does this happen? Can you provide a +12hrs graph of the link quality and RSSI sensor of both devices and probably a bit longer log (~25 minutes)?

[abcklaus]

Link quality of working battery

Link quality of bad battery:

Longer log:

home-assistant_bms_ble_2026-09-08T05-42-25.646Z.log

As described in my initial post: the bluetooth module was replaced by new version. I have asked Supervolt for further information. Waiting for response...

[patman15]

I had a look. Seems that the device goes into some sleep mode and thus not react to requests anymore, only after connection is reestablished. So in my opinion you can try 2 things:

1. Set a custom polling interval of e.g. 10s or
2. disable keep alive setting for the device to force the integration to reestablish the connection each time

I would recommend the first, as the second usually decreases the reliability, but not sure it is enough.

[abcklaus]

Many thanks for your response.

1. using a custom polling interval of 10s did not solve the issue
2. disabling "keep alive" seems to be working. I will observe it during the next days.

Just for my understanding: The new bluetooth doesn't seem to be able to keep a connection. Is that a common behaviour in the "world of BMS"?

[patman15]

You could still try to use 5s (HA won't allow lower values), but I don't give it too much chance.

Just for my understanding: The new bluetooth doesn't seem to be able to keep a connection. Is that a common behaviour in the "world of BMS"?

In general I would say no. That is also the reason, why it is enable by default. I have seen it for some batteries like Lithtech or Liontron. Reason is usually to minimize battery drain when just storing. Some disable it when there is no current, some after a short amount of time.
I guess manufacturers get complains that the battery has a high self discharging rate because users don't understand that the Bluetooth function requires energy ... 😉