MQTT value template to catch NULL

[ha_jsmonty (Justin)]

I have an MQTT topic that can reports a state that sometimes is an number and other times is a null value. How do I build a value template to perform the proper calculation if its a number but allow for the null when present?

For example the below works fine when the value is a number, however when the value flips to “null” I receive the log error “Exception in message_received when handling msg”

#Victron SmartShunt Runtime Remaining
  - unique_id: victron_shunt_battery_timetogo
    name: Battery Runtime Remaining
    device_class: ENERGY_STORAGE
    unit_of_measurement: 'kWh'
    state_topic: "venus-home/N/serial#/battery/288/TimeToGo"
    value_template: "{{(value_json.value / 3600) | round(0) }}"
    icon: mdi:battery

[123 (Taras)]

What value do you want the MQTT Sensor to report when value_json.value isn’t a number?

To clarify, is the received payload always in JSON format and the value key sometimes contains a number and sometimes contains nothing? Post an example or two of the payload.

[ha_jsmonty (Justin)]

Preferably I would love for it to just ignore it until it returns back to a number and it can be calculated. Watching MQTT explorer its consistently a number with a NULL thrown in every now and then.

TimeToGo = {“value”: 863999.9375}
TimeToGo = {“value”: null}

[123 (Taras)]

Try this:

    value_template: >
      {% set v = states('sensor.battery_runtime_remaining') | default(0) %}
      {{ (value_json.value / 3600) | round(0) if value_json.value | is_number else v }}

It reports the newly received value only if it’s a number, otherwise it reports the sensor’s existing value (it reports zero if the sensor has no existing value).

---

EDIT

Correction. Removed errant double-quotes character.

[ha_jsmonty (Justin)]

Got the following error in the logs, the value “50” was correct and matches the source.

Exception raised when updating state of sensor.battery_time_remaining, topic: 'venus-home/N/b827eb39dc65/battery/288/TimeToGo' with payload: b'{"value": 179579.984375}'
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/sensor/__init__.py", line 579, in state
    numerical_value = int(value)
ValueError: invalid literal for int() with base 10: '50"'

[123 (Taras)]

The problem is due to a silly little typo I made in the template I posted above.

There’s a double-quotes character at the end of the second line. Remove it because it shouldn’t be there (it’s a leftover from when I copy-pasted your original template). Its presence is causing the error.

After you remove it, ensure you execute Developer Tools > YAML > Reload Template Entities. The next payload received by the sensor will be stored without the double-quotes character.

---

NOTE

I have already corrected the example posted above and removed the double-quotes character.

[ha_jsmonty (Justin)]

Ah man I thought I fixed it and got excited making it more complicated than it needed to be with the below! Yours works and less code is always better appreciate the help

        value_template: >
            {% set v = states('sensor.battery_runtime_remaining') | default(0) %}
            {% if value_json.value | is_number %}
              {{ (value_json.value / 3600) | round(0) }}
            {% else %}
              v
            {% endif %}

[123 (Taras)]

If you want slightly less code, you can write it like this:

    value_template: >
      {{ (value_json.value / 3600) | round(0) if value_json.value | is_number
        else states('sensor.battery_runtime_remaining') | default(0) }}

[ha_jsmonty (Justin)]

** NOTE: There wasn’t a “reload template entities” in dev tools yaml, but after reloading all yaml I think it is working. Disregard below.

well biscuits. Still erroring when the value returned is null.

Exception raised when updating state of sensor.battery_time_remaining, topic: 'venus-home/N/serial#/battery/288/TimeToGo' with payload: b'{"value": null}'
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/sensor/__init__.py", line 579, in state
    numerical_value = int(value)
ValueError: invalid literal for int() with base 10: 'unknown'

[123 (Taras)]

@ha_jsmonty

There wasn’t a “reload template entities” in dev tools yaml,

@ha_jsmonty

Still erroring when the value returned is null.

Null or unknown? The error message is reporting unknown isn’t an integer value.

As an experiment, let’s see how this behaves:

    value_template: >
      {{ (value_json.value | float(0) / 3600) | round(0) if value_json.value | is_number
        else states('sensor.battery_runtime_remaining') | float(0) }}

[ha_jsmonty (Justin)]

Attached the reloading options I have in dev tools page. The template is working fine UNLESS I reload HA while the battery is fully charged or charging. When ever the battery is fully charged and not draining is when the MQTT value is being sent as “null”. I noticed on another users example they were showing the state as “charging”, is there a way to build the template to show the time remaining OR the value “charging” ?

[123 (Taras)]

@ha_jsmonty

Attached the reloading options I have in dev tools page

Not sure why Template Entities doesn’t appear on the reloading page. I would expect that if you didn’t have any Template entities defined but you do.

@ha_jsmonty

is there a way to build the template to show the time remaining OR the value “charging” ?

Your Template Sensor employs the unit_of_measurement option which (as of version 2023.5.0) demands that the entity’s value is numeric. Therefore you can’t have the template produce a non-numeric value like “charging”.

Did you get a chance to test the latest template I had proposed?

[ha_jsmonty (Justin)]

Its not a historically important value, is it possible to use a different template that can display a numerical number or a string?

I have the updated value template you sent loaded, after the sensor got its first numerical value its working fine, showing 0 when the value returned is “null” and showing the actual numerical value when present.

[123 (Taras)]

@ha_jsmonty

possible to use a different template that can display a numerical number or a string?

Yes, the template can be designed to report whatever you want but it’s the presence of other options, such as unit_of_measurement, that determines if the overall Template Sensor will work properly or generate error messages.

Glad to hear the revised template works properly.

[ha_jsmonty (Justin)]

Did some more digging and found the following sensor configuration in a setup guide, going to give it a try and see how it functions. Appreciate the help and education Taras!

  # Estimated Time until battery is empty based on current load.
  # These calculations were copied from victrons code to mimic how they display it
  - name: "Battery Remaining"
    icon: mdi:timer-sand
    state_topic: "victron/N/your-venus-id/system/0/Dc/Battery/TimeToGo"
    value_template: >
      {% if value == '{"value": null}' %}
        ∞
      {% else %}

        {% set seconds = value_json.value | round(0) | int %}
        {% set days = (seconds / 86400) | round(0, 'floor') | int %}
        {% set hours = ((seconds - days * 86400) / 3600) | round(0, 'floor') | int %}
        {% set minutes = ((seconds - hours * 3600) / 60) | round(0, 'floor') | int %}

        {% if 2 > days >= 1 %}
          {{days}} Day
        {% elif days >= 2 %}
          {{days}} Days
        {% elif hours > 0 %}
          {{hours}} Hours
        {% elif minutes > 0 %}
          {{minutes}} Minutes
        {% else %}
          ∞
        {% endif %}
      {% endif %}

[123 (Taras)]

You may also wish to consider using relative_time to display elapsed time.

Reference: Templating