Car charging

As a bare minimum a HA-controllable smart plug with a granny charger could be used, but do consider there could be an electrical spike to the car if the smart plug is turned off when the car is charging. A proper car charger and HA integration is preferable.

You will firstly need to have installed the appropriate Home Assistant integration for your car charger.

Configure apps.yaml for your car charging

Start by configuring the Car charging settings in apps.yaml.

Car Charging Planning

There are two ways that Predbat can plan the slots for charging your car:

  • If you have the Intelligent Octopus import tariff, have completed enrollment of your car/charger to Intelligent Octopus (requires a compatible charger or car), and you have installed the Octopus Energy integration - in which case Predbat will use the car charging slots allocated by Octopus Energy in battery prediction. The Octopus Energy integration supports Octopus Intelligent, and through that Predbat gets most of the information it needs.

    • octopus_intelligent_slot in apps.yaml is pre-configured with a regular expression to point to the Intelligent Slot sensor in the Octopus Energy integration. You should not need to change this, but its worth checking the Predbat logfile to confirm that it has found your Octopus account details
    • Set switch.predbat_octopus_intelligent_charging to True
    • Information about the car's battery size will be automatically extracted from the Octopus Energy integration
    • You should set the cars current soc sensor, car_charging_soc in apps.yaml to point to a Home Assistant sensor that specifies the car's current % charge level to have accurate results. This should normally be a sensor provided by your car charger If you don't have this available for your charger then Predbat will assume the car's current charge level is 0%
    • If you set car_charging_limit in apps.yaml then Predbat can also know if the car's limit is set lower than in Intelligent Octopus. If you don't set this Predbat will default to 100%.
    • You can use car_charging_now as a workaround to indicate your car is charging but the Intelligent API hasn't reported it
    • The switch switch.predbat_octopus_intelligent_ignore_unplugged (expert mode) can be used to prevent Predbat from assuming the car will be charging when the car is unplugged. This will only work correctly if car_charging_planned is set correctly in apps.yaml to detect your car being plugged in
    • Let the Octopus app control when your car charges.

  • Predbat-led charging - Here Predbat plans and can initiate the car charging based on the upcoming low import rate slots

    • Ensure car_charging_limit, car_charging_soc and car_charging_planned are set correctly in apps.yaml to point to the appropriate sensors from your EV (see Car charging config in apps.yaml)
    • Check (and if necessary add) the sensor response value from the sensor configured in car_charging_planned that is returned when the car is 'plugged in and ready to charge' is in the list of car_charging_planned_response values configured in apps.yaml
    • If your car does not have a state of charge (SoC) sensor you can set switch.predbat_car_charging_manual_soc to True to have Predbat create input_number.predbat_car_charging_manual_soc_kwh which will hold the cars SoC in kWh.
      You will need to manually set this to the cars current charge level before charging, Predbat will increment it during charging sessions but will not reset it automatically.
      NB: input_number.predbat_car_charging_manual_soc_kwh must be set to the current kWh value of your car battery NOT a percentage SoC figure otherwise Predbat won't know how much energy there currently is in the battery.
      NB2: If you have car_charging_soc set and working for your car SoC sensor in apps.yaml, switch.predbat_car_charging_manual_soc must be set to Off as otherwise the car SoC sensor will be ignored
    • Ensure switch.predbat_octopus_intelligent_charging in Home Assistant is set to Off
    • Set input_number.predbat_car_charging_rate to the car's charging rate in kW per hour (e.g. 7.5 for 7.5kWh)
    • Set select.predbat_car_charging_plan_time to the time you want the car charging to be completed by
    • Turn on switch.predbat_car_charging_plan_smart if you want to use the cheapest slots only. When disabled (turned off) all low rate slots will be used in time order
    • You can set input_number.predbat_car_charging_plan_max_price if you want to set a maximum price in pence per kWh to charge your car (e.g. 10p). If you set this to zero, this feature is disabled, and all low rate slots will be used. This may mean you need to use expert mode and change your low rate threshold to configure which slots should be considered if you have a tariff with more than 2 import rates (e.g. Flux)
    • WARNING: Do not set car_charging_now or you will create a circular dependency.
    • Predbat will set binary_sensor.predbat_car_charging_slot when it determines the car can be charged; you will need to write a Home Assistant automation based on this sensor to control when your car charges.
      A sample automation to start/stop car charging using a Zappi car charger and the MyEnergi Zappi integration is as follows, this should be adapted for your own charger type and how it controls starting/stopping car charging:
alias: Car charging
description: "Start/stop car charging based on Predbat determined slots"
triggers:
  - trigger: state
    entity_id:
      - binary_sensor.predbat_car_charging_slot
actions:
  - choose:
      - conditions:
          - condition: state
            entity_id: binary_sensor.predbat_car_charging_slot
            state: "on"
        sequence:
          <commands to turn on your car charger, e.g.>
          - service: select.select_option
            data:
              option: Eco+
            target:
              entity_id: select.myenergi_zappi_charge_mode
      - conditions:
          - condition: state
            entity_id: binary_sensor.predbat_car_charging_slot
            state: "off"
        sequence:
          <commands to turn off your car charger, e.g.>
          - service: select.select_option
            data:
              option: Stopped
            target:
              entity_id: select.myenergi_zappi_charge_mode
mode: single

NOTE: Multiple cars can be planned with Predbat.

Additional Car charging configurations

If you have one charger and multiple cars configured in Predbat then set car_charging_exclusive in apps.yaml to True to indicate that only one car may charge at once (the first car reporting as plugged in will be considered as charging). If you set this to False then it is assumed each car can charge independently and hence two or more could charge at once

car_charging_exclusive:
  - True
  - True

See Car charging filtering and Planned car charging in the apps.yaml settings section of the documentation.

  • switch.predbat_car_charging_from_battery - When set to True the car can drain the home battery, Predbat will manage the correct level of battery accordingly. When set to False home battery discharge will be prevented when your car charges, all load from the car and home will be from the grid. This is achieved by setting the battery discharge rate to 0 during car charging and to the maximum otherwise. The home battery can still charge from the grid/solar in either case. Only use this if Predbat knows your car charging plan, e.g. you are using Intelligent Octopus or you use the car slots in Predbat to control your car charging.

  • input_number.predbat_car_charging_loss gives the percentage amount of energy lost when charging the car (load in the home vs energy added to the battery). A good setting is 0.08 which is 8%.

Example EV and charger setup

Sample setup and Predbat automation to use the cheapest charging slots with no/limited Home Assistant Integration.

MG4 EV Vehicle with a Hypervolt Car Charger. There is no 3rd party integration with the MG, and the Hypervolt car charger doesn't understand when an EV is plugged in.

Yet it can be stopped and started with a 3rd party integration.

In Home Assistant, create two helper entities (Settings / Devices & Services / Helpers) of type 'Number', and for each set 'Unit of Measurement' to 'kWh':

  • Car Max Charge - input_number.car_max_charge
  • Car Manual SoC - input_number.car_manual_soc

Create a 'Dropdown' helper entity that has two options 'true' and 'false' (in lower case):

  • Car Charger Plugged in - input_select.car_charger_plugged_in

Within the apps.yaml configuration file specify the following configuration settings:

Find the line for car_charger_battery_size and enter the Car Battery Size in kWh:

Example

  car_charging_battery_size:
    - 61.7

Specify the Car Charging Limit to use the Car Max Charge helper entity created earlier:

  car_charging_limit:
    - 'input_number.car_max_charge'

Find car_charging_planned and replace the template Wallbox and Zappi regular expression with your new dropdown helper entity:

  car_charging_planned:
    - 'input_select.car_charger_plugged_in'

Find car_charging_planned_response and add 'true' to the list:

  car_charging_planned_response:
    - 'yes'
    - 'on'
    - 'true'

If possible, add an entity keeping track of the kWh used for car charging to car_charging_energy.

If your charging device doesn't keep track of kWh but you can measure the power sent to the car charger (e.g. from the EV charger integration or an energy monitor/smart plug for the EV charger) then you can create another helper entity to convert kW power into kWh:

Create a helper entity (Settings / Devices & Services / Helpers) of type 'Integration - Riemann Sum integral':

  • Name : car_energy_used
  • Input sensor : sensor that measures power consumed by the car charger
  • Integration method : Right Riemann sum
  • Metric prefix : k (kilo)

Please look into Integration - Riemann sum integral to convert kW into kWh.

And add your custom car charging energy sensor in apps.yaml in place of the template Wallbox and Zappi regular expression:

Example

car_charging_energy: 'sensor.car_energy_used'

car_charging_now must be commented out (hashed out) in apps.yaml:

  #car_charging_now:
  #  - off

Save the apps.yaml file and exit.

In Home Assistant, turn on the following Predbat control switches:

  • switch.predbat_car_charging_hold
  • switch.predbat_car_charging_manual_soc
  • switch.predbat_car_charging_plan_smart

And turn off the Predbat control switch:

  • switch.predbat_octopus_intelligent_charging

HA Charging Slot Automation

In Home Assistant (Settings / Automation & Scenes), create an automation to monitor the Predbat car charging slot sensor and turn the charger on and off according to the Predbat plan (the numeric entity id's below would need replacing with the appropriate sensor name for your car charger):

alias: Car Charging Slot
description: ""
triggers:
  - trigger: state
    entity_id:
      - binary_sensor.predbat_car_charging_slot
actions:
  - if:
      - condition: state
        entity_id: binary_sensor.predbat_car_charging_slot
        state: "off"
    then:
      - type: turn_off
        entity_id: f6de2df0758744aba60f6b5f
        domain: switch
  - if:
      - condition: state
        entity_id: binary_sensor.predbat_car_charging_slot
        state: "on"
    then:
      - type: turn_on
        entity_id: f6de2df0758744aba60f6b5f
        domain: switch
mode: single

Finally, for simplicity, add the below entities to your HA Dashboard so you can set them when needed:

  • Car Max Charge - input_number.car_max_charge
  • Car Manual SoC - input_number.car_manual_soc
  • Car Charger Plugged in - input_select.car_charger_plugged_in

Annoyingly, you have to calculate the kWh your vehicle has in total by taking the Percentage left in the car / 100 * Total Car Battery capacity.
For example:

65/100*61.7=40.1

Enter '40.1' into 'Car Manual SoC' and '80%' into 'Car Max charge'.

Once the charger is switched to true and your Car Max charge (target SoC) % is higher than the kWh currently in the car, Predbat will plan and charge the car with the kW that are needed to reach the target SoC.