[HELP] MQTT stops publishing for 4-6 minutes while Web UI continues to show live data

[netzspezialist]

Hi everyone,

I am experiencing a specific issue with my Daly2MQTT BMS Dongle where the MQTT transmission drops out, but the device itself remains active.

The Problem:

• The dongle is set to a 20-second update interval.
• Regularly, MQTT messages stop being sent for a duration of 4 to 6 minutes.
• Crucial Observation: During these "silent" MQTT periods, the Web UI of the dongle still updates and displays live data from the BMS.

Technical Details:

• Connectivity: The Web UI is reachable, and the WiFi connection is stable.
• Broker: Other devices continue to send data to the same broker without issues.
• Recovery: After the 4-6 minute gap, MQTT messages start flowing again automatically without a manual reboot.

Analysis:
Since the Web UI shows live data, the communication between the Dongle and the BMS (UART) is working perfectly. The issue seems to be isolated to the MQTT client/service within the firmware, which appears to hang or lose its connection silently before eventually recovering.

Questions:

• Is there a known bug where the MQTT client stops publishing even though the data acquisition is still running?
• Are there any specific MQTT settings (Keep Alive, Clean Session, etc.) that could be causing this "timeout and recovery" cycle?
• How can I provide more detailed logs from the MQTT stack to help diagnose this?

Thank you for your support!

Additional context

No response

[netzspezialist]

Update on my investigation:

I have been running a Python-based WebSocket logger on a Raspberry Pi 5 to monitor the /ws endpoint directly.
New Findings:

• Contrary to my initial observation, the WebSocket stream also experiences gaps, although they appear to be shorter than the MQTT outages.
• During these gaps, the device remains pingable, but no data is pushed through either MQTT or WS.
• This suggests that the issue is not isolated to the MQTT client, but rather a hang in the main data acquisition loop or a resource exhaustion (CPU/RAM) on the dongle itself.

Log evidence:
I have attached a snippet of the log showing the timestamps where the data flow stops and resumes.

2026-02-27 10:24:05,013 - DATA: {"Device":
2026-02-27 10:26:06,087 - DATA: {"Device": <-- Gap of 2 minutes

Does the firmware implement any watchdog or heavy background tasks (like internal flash writing or WiFi re-scans) that could block the main loop for this long?

2026-02-27 10:24:02,709 - DATA: {"Device":{"Name":"Daly2MQTT","IP":"192.168.88.8","Flash_Size":4194304,"Sketch_Size":465472,"Free_Sketch_Space":3706880,"CPU_Frequency":80,"Real_Flash_Size":4194304,"ESP_VCC":3.774,"Wifi_RSSI":-55,"Relais_Active":false,"Relais_Manual":false,"sw_version":"2.15.1","Free_Heap":25648,"json_space":1326,"runtime":11007,"ws_clients":1,"MQTT_Json":true},"Pack":{"Voltage":54,"Current":68.3,"Power":3688.2,"SOC":81.9,"Remaining_Ah":450.5,"Remaining_kWh":24.327,"Cycles":207,"BMS_Temp":24,"Cell_Temp":24,"cell_hVt":3.65,"cell_lVt":2.3,"cell_hVt2":3.52,"cell_lVt2":3,"pack_hVt":58.4,"pack_lVt":36.8,"pack_hVt2":56.5,"pack_lVt2":44.8,"High_CellNr":16,"High_CellV":3.386,"Low_CellNr":8,"Low_CellV":3.372,"Cell_Diff":14,"DischargeFET":true,"ChargeFET":true,"Status":"Charge","Cells":16,"Heartbeat":183,"Balance_Active":false,"Fail_Codes":""},"CellV":{"CellV_1":3.375,"CellV_2":3.377,"CellV_3":3.376,"CellV_4":3.375,"CellV_5":3.375,"CellV_6":3.375,"CellV_7":3.373,"CellV_8":3.373,"CellV_9":3.373,"CellV_10":3.375,"CellV_11":3.375,"CellV_12":3.375,"CellV_13":3.377,"CellV_14":3.379,"CellV_15":3.383,"CellV_16":3.386},"CellTemp":{"Cell_Temp_1":24}}

2026-02-27 10:24:05,013 - DATA: {"Device":{"Name":"Daly2MQTT","IP":"192.168.88.8","Flash_Size":4194304,"Sketch_Size":465472,"Free_Sketch_Space":3706880,"CPU_Frequency":80,"Real_Flash_Size":4194304,"ESP_VCC":3.772,"Wifi_RSSI":-55,"Relais_Active":false,"Relais_Manual":false,"sw_version":"2.15.1","Free_Heap":25648,"json_space":1326,"runtime":11009,"ws_clients":1,"MQTT_Json":true},"Pack":{"Voltage":54,"Current":71.6,"Power":3866.4,"SOC":81.9,"Remaining_Ah":450.5,"Remaining_kWh":24.327,"Cycles":207,"BMS_Temp":24,"Cell_Temp":24,"cell_hVt":3.65,"cell_lVt":2.3,"cell_hVt2":3.52,"cell_lVt2":3,"pack_hVt":58.4,"pack_lVt":36.8,"pack_hVt2":56.5,"pack_lVt2":44.8,"High_CellNr":16,"High_CellV":3.387,"Low_CellNr":7,"Low_CellV":3.373,"Cell_Diff":14,"DischargeFET":true,"ChargeFET":true,"Status":"Charge","Cells":16,"Heartbeat":185,"Balance_Active":false,"Fail_Codes":""},"CellV":{"CellV_1":3.375,"CellV_2":3.377,"CellV_3":3.377,"CellV_4":3.375,"CellV_5":3.375,"CellV_6":3.375,"CellV_7":3.373,"CellV_8":3.373,"CellV_9":3.375,"CellV_10":3.375,"CellV_11":3.374,"CellV_12":3.375,"CellV_13":3.379,"CellV_14":3.379,"CellV_15":3.383,"CellV_16":3.387},"CellTemp":{"Cell_Temp_1":24}}

2026-02-27 10:26:06,087 - DATA: {"Device":{"Name":"Daly2MQTT","IP":"192.168.88.8","Flash_Size":4194304,"Sketch_Size":465472,"Free_Sketch_Space":3706880,"CPU_Frequency":80,"Real_Flash_Size":4194304,"ESP_VCC":3.775,"Wifi_RSSI":-54,"Relais_Active":false,"Relais_Manual":false,"sw_version":"2.15.1","Free_Heap":26000,"json_space":1326,"runtime":11130,"ws_clients":1,"MQTT_Json":true},"Pack":{"Voltage":53.5,"Current":8.3,"Power":444.05,"SOC":82.2,"Remaining_Ah":452.1,"Remaining_kWh":24.18735,"Cycles":207,"BMS_Temp":24,"Cell_Temp":24,"cell_hVt":3.65,"cell_lVt":2.3,"cell_hVt2":3.52,"cell_lVt2":3,"pack_hVt":58.4,"pack_lVt":36.8,"pack_hVt2":56.5,"pack_lVt2":44.8,"High_CellNr":16,"High_CellV":3.35,"Low_CellNr":11,"Low_CellV":3.34,"Cell_Diff":10,"DischargeFET":true,"ChargeFET":true,"Status":"Charge","Cells":16,"Heartbeat":50,"Balance_Active":false,"Fail_Codes":""},"CellV":{"CellV_1":3.348,"CellV_2":3.348,"CellV_3":3.348,"CellV_4":3.348,"CellV_5":3.346,"CellV_6":3.346,"CellV_7":3.344,"CellV_8":3.342,"CellV_9":3.34,"CellV_10":3.342,"CellV_11":3.34,"CellV_12":3.342,"CellV_13":3.342,"CellV_14":3.344,"CellV_15":3.348,"CellV_16":3.35},"CellTemp":{"Cell_Temp_1":24}}

2026-02-27 10:26:08,428 - DATA: {"Device":{"Name":"Daly2MQTT","IP":"192.168.88.8","Flash_Size":4194304,"Sketch_Size":465472,"Free_Sketch_Space":3706880,"CPU_Frequency":80,"Real_Flash_Size":4194304,"ESP_VCC":3.773,"Wifi_RSSI":-54,"Relais_Active":false,"Relais_Manual":false,"sw_version":"2.15.1","Free_Heap":26000,"json_space":1326,"runtime":11133,"ws_clients":1,"MQTT_Json":true},"Pack":{"Voltage":53.5,"Current":7.9,"Power":422.65,"SOC":82.2,"Remaining_Ah":452.1,"Remaining_kWh":24.18735,"Cycles":207,"BMS_Temp":24,"Cell_Temp":24,"cell_hVt":3.65,"cell_lVt":2.3,"cell_hVt2":3.52,"cell_lVt2":3,"pack_hVt":58.4,"pack_lVt":36.8,"pack_hVt2":56.5,"pack_lVt2":44.8,"High_CellNr":16,"High_CellV":3.35,"Low_CellNr":11,"Low_CellV":3.34,"Cell_Diff":10,"DischargeFET":true,"ChargeFET":true,"Status":"Charge","Cells":16,"Heartbeat":53,"Balance_Active":false,"Fail_Codes":""},"CellV":{"CellV_1":3.348,"CellV_2":3.348,"CellV_3":3.348,"CellV_4":3.347,"CellV_5":3.346,"CellV_6":3.346,"CellV_7":3.344,"CellV_8":3.342,"CellV_9":3.34,"CellV_10":3.342,"CellV_11":3.34,"CellV_12":3.342,"CellV_13":3.342,"CellV_14":3.344,"CellV_15":3.346,"CellV_16":3.35},"CellTemp":{"Cell_Temp_1":24}}

2026-02-27 10:26:10,681 -

[netzspezialist]

WebSerial:
NO DATA
Receive failed 148
NO DATA
Receive failed 148
NO DATA
Receive failed 148
NO DATA
Receive failed 148
NO DATA
Receive failed 148
NO DATA
Receive failed 148
NO DATA
Receive failed 148
NO DATA
Receive failed 148
Data sent to WebSocket
NO DATA
Receive failed 148
NO DATA
Receive failed 148

-->open daly2mqtt WebUI in Browser!

Data sent to MQTT Server
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to MQTT Server
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to WebSocket
Data sent to MQTT Server
Data sent to WebSocket

[softwarecrash]

hello, thanks for the log.
i never seen this in this way.
but its possible that it hang when it not recive date from the bms or communication with bms fails. the NO DATA looks like this.
the websocket is a standalone thing that works with ticks and alive pings, but can stop too when not new data is incomming.

there are no active load tasks while normal operation like scans or flashing

[MatchoLM]

Hi I got similar issue, i have 4 batteries all with same BMS. on all ESP D1 mini same FW 2.15.1 from release date (perfect working more then 6monts) . just several days ago on one battery i stop getting informations from BMS - but partiatli i got volatage and so but no cells voltage and number of cycles, also MQTT stop working. today i try to revert to 2.15.0 and i dont understand what happened but readings is against working including MQTT. just for test i went back to 2.15.1 and issue persist. @Cheng-Logic try to use 2.15.0 as i did and let us know if it help also for you.

[soeren487]

Same behavior for me as for @MatchoLM. Have two batteries running, both were on 2.15.1. One got the issue several days ago: Receive failed 148. The second still works as expected. Seems to be an issue in the Serial communication with the BMS. Maybe a timing failure in the communication protocol, due to the 2.15.1 update. I re-enrolled 2.15.0 to both of them. With that both are working. The one with the issue works also stable, no hardware changes made.

[softwarecrash]

hey there,
please try this fix

Daly2MQTT_d1_mini_2.15.1-dev-0.1.zip

[MatchoLM]

Hi just tested on problematic battery and it looks okay to me :)