Tesla-PV-charging

Description:

Home-Assistant can talk to all common photovoltaic systems, and it can talk to your Tesla car. So let's use Home-Assistant to charge the car with your spare PV power! :)

This documents my solution to charge my Tesla with PV excess. I own a Tesla Model 3, a Huawei PV system with 8.5kW peak and 10kWh battery. The Tesla is plugged into a "dumb" wallbox that can charge with 11kW (3-phase). All charge control is done via the car API, the wallbox is dumb and does just safety stuff. You plug the car into the wallbox, and it turns on the power.

My aim is to both use the home-battery as a buffer to allow smoother charging of my Tesla, and to make sure that my house battery is charged to 90-100% at the end of the day. Also, it allows me to use a simple wall-box which is around 350 Euro vs the not-so-smart boxes in the 600-1000 Euro-range. We can drive the charing power in the range of 0.7kW to 11kW, that's smoother than the expensive wall boxes and we don't need to fuss around with 1/3-phase-charging and the issues many boxes have when they switch mode.

This approach works well for me - I have run my Tesla for 19,000km so far, and except during the winter, it operates solely on solar excess power.

Why did I go the extra mile, when there are ready-made solutions? I looked into EVCC - it relies on smart (=expensive and complicated) wall-boxes, and is limited by the capabilities of the wallbox. It can't charge slower than the wallbox allows, which is an issue especially if the box can't switch 1/3-phase-charging. I also looked into Tesla Solar Charger. It doesn't need a special wallbox, but its charging strategies are not very flexible when it comes to balancing energy between house- and vehicle-battery.

How does it do that?

It monitors the PV output from the roof and the current state of the house battery. There are three main stages in the daily charging cycle:

When the house battery is below 40%, charging the house battery has full priority. No charging of the car is done, except when the PV output is very high and the house battery can't take all the power.
When the house battery is between 40% and 75%, 70% of the unused PV power is used to charge the car, the rest is taken by the house battery. Since the house battery is just a fraction of the car battery, that quota is generally enough to fill the house battery over the day.
When the house battery is between 75% and 90%, the car is charged at 80% solar output but keeping a minimum of 4kW (6Ax3) to speed up charging.
When the house battery is charged beyond 90%, the car gets the full surplus. Since we round off to the next lower ampere setting, some power will still go into the house battery.
Hysteresis: For the transition between the three stages, a hysteresis of 3-5% is built into each formula to make sure don't continually jump up and down with every cloud on the sky. This is where the house battery comes very handy: We can afford to smooth the current a bit by using the household battery as a buffer.
Charge with 0A: This is something the "smart wallboxes" can't do. When the PV output goes down due to clouds, we tell the car to charge at 0A, but keep the connection alive. We don't want the car to open and close the big relais every few minutes when the weather is shady.
Express mode: I added an "Express mode" which aims to charge the car battery as fast as possible and uses house battery energy in addition to solar output. This is practical for days when I need to head to the office, but expect lots of sunshine. It makes sense to shift battery power into the car and then have the house battery recharge during the day. This stops automatically at 20% SOC of the house battery. The formula does also minds the combined maximum inverter power. My PV can deliver 8.5kW max, my house battery can deliver 5kW, but the inverter is limited to 10kW maximum power. So the consumption has to stay below 10kW to avoid grid import.

Prerequisites:

You should own a photovoltaic system with enough power to charge your car, with a reasonably sized battery. My system has 8.5kW peak power and a 15kWh battery. You can go lower on the PV power, but it will take longer to charge your car, obviously. The size of the battery is not really important. It will just work as a buffer and even a small 3kWh unit should be just fine. My system is made by Huawei, a Sun2000-10-KTL-M1 with their matching smart-meter and their matching Luna2000 battery. Since I don't use any proprietary functions, it is easy to adapt. I use standard numbers like inverter input power, battery SOC and so on that any standard PV system will provide.

A wallbox (if you charge 3-phase) or the Tesla AC charger that plugs into any ac wallplug. There is no need for the wallbox to have any management capabilities. In fact, this stuff works easier with a wallbox that just charges and doesn't require any commands to do its job.

Then you want Home-Assistant as a house automation system. It is the foundation for what we do here. Home-Assistant has plenty of integrations into the typical house stuff like wall plugs, heating valves and so on. There are integrations for all the common PV brands through a community-managed integration appstore called HACS. You can run Home-Assistant on a Raspberry Pi or similar small computers. The company behind Home-Assistant does also sell ready-to-use systems with their own hardware. If you can find or have a Raspberry Pi at hand, it's cheaper and just fine.

Steps:

1. Installation: I assume you have a working Home Assistant installation

1.1 You need to install HACS (Home Assistant Community Store), it's needed to install the integrations for your PV system and for the Tesla car.

1.2 You should install "Studio Code Server", it's a comfortable editor the the Home Assistant configuration files.

1.3 In HACS, install the Tesla integration and connect it with your Tesla car. There is a good documentation in the HACS page, especially for creating the "tokens" you need to let HA talk with your car.

1.4 In HACS, install the integration for your PV system and connect it with your local PV system. You don't need all the bells an whistles, the numbers for PV output in Watt and the state of charge of your house battery in percent is all you really need for this. If you can configure the update intervall, 30s or less is a good starting point.

2. Get familiar with the integrations:

Get to know the Tesla and PV integrations before you continue. Especially, you should get a feeling on how fast the integrations update and check if your Tesla updates the location and the charging port status when you get home and plug the cable in.

3. Sensors: Now, we will create a few sensors and variables that are needed to control the PV current.

3.1 In Settings/Devices/Helpers, create the following helpers. Keep in mind: My car is called "Tesla" in HA. If yours is Coolest-car-ever, you will want to change the entity names from "xxx.Tesla-xxx" to "xxx.Coolest-car-ever.xxx":

Chose the type "number", set to 75 as a starting point:

Chose the type "toggle", set to off as a starting point:

Chose the type "number", set to 0 as a starting point:

Chose the type "toggle", set to off as a stating point:

Chose the type "Threshold sensor":

3.2 In Studio Code Server, open the file "configuration.yaml" and add the following sensors.

Attention:

The entities sensor.battery_state_of_capacity and sensor.inverter_input_power are specific to my Huawei PV system. If you run a Fronius, SolarEdge, Victron, Sungrow or whatever PV system, you will need to find the right entity names for your system.

My car is called "Tesla", therefore the entities for my car have "tesla" after the dot. If your cars name is "godzilla", you need to change that to ie sensor.godzilla_charger_power .


- sensor:
- name: 'Autocharge-optimal'
  unit_of_measurement: "A"
  state: > 
    {# calculate the optimal charge current based on several parameters: #}
    {# PV yield, house battery SOC, vehicle battery SOC, Grid consumption #}
    {% set PV = states('sensor.filtered_inverter_power')|float -500 %}
    {% set Battery = states('sensor.battery_state_of_capacity')|float (0) %}
    {% set Grid = states('sensor.power_meter_active_power') |float (0) %}
    {% set Charge = states('sensor.tesla_charger_power')|float %}
    {% set Throttle = states('input_number.tesla_charge_break') |float %}
    {% set Endoffastcharge = states('input_number.num_battery_min_home') |float %}
    {% set Teslabattery = states('sensor.tesla_battery') |float (0) %}
    {% set BatteryMaxDischarge = 4500 %}

    {# if Grid>0 %} {% set Grid = 0 %} {% endif #}
    {# PV/230 is the current in a one phase system. For three-phase charging divide by 3! #}
    {% set PVAMP = (PV/230/3) %}
    {% if Battery>97 %} {% set PVAMP = PVAMP+1 %} {% endif %}
    {# While the house battery is below 90% ist, use only 70% of the output so the house battery will charge, too #}
    {% if Battery<90 %} {% set PVAMP = (PVAMP*0.7) %} {% endif %}
    {% if (Teslabattery>90) and (Battery<80) %} {% set PVAMP = PVAMP * 0.5 %} {% endif %}
    {# When the house battery is above "Endoffastcharge", use at least 6A. When starting, use +5 for hysteresis #}
    {% if (PVAMP<6) and (Battery>Endoffastcharge+5 )  %}  {% set PVAMP = 6 %} {% endif %} 
    {% if (PVAMP<6) and (Battery>Endoffastcharge) and (Charge>0) %} {% set PVAMP = 5 %} {% endif %} 
    {# Under 40%, charge only the house battery, not the car. 3% hysteresis: Don't turn on until we reach 43%. #}
    {# Exception: When the PV output is really high, allow charging so we don't feed to the grid early #}
    {% if (Battery<43) and (Charge==0) and (PVAMP<6) %} {% set PVAMP = 0 %} {% endif %} 
    {% if (Battery<40) and (Charge>0) and (PVAMP<6) %} {% set PVAMP = 0 %} {% endif %} 
    {% if (PVAMP>6) and (Battery<40) %} {% set PVAMP = 3 %} {% endif %}
    {# Don't start charging under 3A because it's not efficient. #}
    {% if (PVAMP<3) and (Charge==0) %} {% set PVAMP = 0 %} {% endif %}
    {# Under very high load, like cooking at noon, use throttle. Throttle is controlled by an automation #}
    {% set PVAMP = PVAMP - Throttle %}
    {% if Grid < -300 %} {% set PVAMP = PVAMP + (Grid/230/3) %} {% endif %}
    {% if is_state('input_boolean.tesla_express', 'on') and (Battery>20) %} {% set PVAMP = ((PV + BatteryMaxDischarge + Grid)/230/3) |int %} {% endif %}
    {% if PVAMP>14 %} {% set PVAMP = 14%} {% endif %}
    {# avoid negative numbers. They are technically irrelevant, but irritating #}
    {% if PVAMP<0 %} {% set PVAMP = 0%} {% endif %}
    {{ PVAMP|int }}

- sensor:
- name: 'Autocharge-Difference'
  unit_of_measurement: "A"
  state: > 
    {# if there is a difference between optimal charge current and actual charge current, calculate the absolute value #}
    {% set CHARGE = states('number.tesla_charging_amps')|float (0) %}
    {% set REQUIRED = states('sensor.autocharge_optimal') |float (0) %}
    {% set DIFF = (CHARGE - REQUIRED)|abs %}
    {{ DIFF|int }}

sensor:

platform: filter name: "filtered inverter power" entity_id: sensor.inverter_input_power filters:
- filter: time_simple_moving_average window_size: "00:03" precision: 0


### 4. Automations:

We need several automations. Unfortunately, they can grow pretty long, and there is no really good way to export them. So sorry if I can only give you some very huge screenshots. If anybody know a tool for making better visual representations, please let me know.

   4.1 Tesla-Charge-Adjust: This most important one will simply start every 60s and, after checking the car is at home and wired for charging, set the right current and start or stop the charging process.

   <img src="https://github.com/top-gun/Tesla-PV-charging/blob/main/pictures/Extended-Charge-Adjust.png" width=300>

For the ease of debugging, here is the YAML definition:

alias: Tesla-Charge-Adjust description: When the car is home and charging, adjust the charging power to the PV output trigger:

platform: time_pattern minutes: /1 condition:
type: is_plugged_in condition: device device_id: 6c8ec0c37f65e3a882fbb667e1e5f108 entity_id: binary_sensor.tesla_charger domain: binary_sensor
condition: device device_id: 6c8ec0c37f65e3a882fbb667e1e5f108 domain: device_tracker entity_id: device_tracker.tesla_location_tracker type: is_home
condition: state entity_id: input_boolean.auto_manuell state: "off" action:
if:
- condition: numeric_state entity_id: sensor.autocharge_optimal above: 1
- type: is_not_charging condition: device device_id: 6c8ec0c37f65e3a882fbb667e1e5f108 entity_id: binary_sensor.tesla_charging domain: binary_sensor then:
- type: turn_on device_id: 6c8ec0c37f65e3a882fbb667e1e5f108 entity_id: af4dad29a62461eaf513223c2649107c domain: switch
if:
- condition: state entity_id: binary_sensor.charge_no_current state: "on" for: hours: 0 minutes: 5 seconds: 0
- type: is_charging condition: device device_id: 6c8ec0c37f65e3a882fbb667e1e5f108 entity_id: binary_sensor.tesla_charging domain: binary_sensor then:
- type: turn_off device_id: 6c8ec0c37f65e3a882fbb667e1e5f108 entity_id: switch.tesla_charger domain: switch enabled: true
- device_id: 6c8ec0c37f65e3a882fbb667e1e5f108 domain: number entity_id: 8dfa97ec39cf127ff8849a9370377e7d type: set_value value: 6 enabled: true
if:
- condition: numeric_state entity_id: sensor.autocharge_difference above: 1
- condition: and conditions:
  - condition: state entity_id: switch.tesla_charger state: "on" then:
- service: number.set_value data_template: entity_id: number.tesla_charging_amps value: >- {% set optimal_amps = states('sensor.autocharge_optimal') | int %} {{ optimal_amps }} enabled: true mode: single


   4.2 Tesla-Leaving: When the car leaves home, set the charge mode to automatic and the house battery to 75% minimum for fast charging.

   <img src="https://github.com/top-gun/Tesla-PV-charging/blob/main/pictures/Advanced-Tesla-Leaving.png" width=300>

   4.3 Tesla-1800-charge-socket-90p: At 6PM, set the minimum socket for the house battery to 90% so the house battery gets as full as possible

   <img src="https://github.com/top-gun/Tesla-PV-charging/blob/main/pictures/Automation-1800-socket-90p.png" width=300>

   4.4 Tesla-throttle-high-load: You may run into situations where high house load and high car charging exceed the inverter capacity. My inverter is capable of 11,000W, I set the threshold to 10,500W. Adjust to about 5% below your inverter's capacity.

   <img src="https://github.com/top-gun/Tesla-PV-charging/blob/main/pictures/Automation-throttle-charge-high-load.png" width=300>

   4.5 Tesla-polling-6AM: Start polling the car status at 6:30AM. We stop polling at 11PM to make sure the car can actually sleep.

   <img src="https://github.com/top-gun/Tesla-PV-charging/blob/main/pictures/Automation-turn-on-polling-6AM.png" width=300>

   4.6 Tesla-stop-polling-11PM: Stop polling at 11PM to make sure the car can actually sleep.

   <img src="https://github.com/top-gun/Tesla-PV-charging/blob/main/pictures/Automation-turn-off-polling-11PM.png" width=300>

### 5. Fancy visualization:

Basically, your car can charge without any intervention. Still, we like to monitor and control, so I made a dashboard for this. It requires two extra front-end extensions which you can download in HACS:

   5.1 Power Flow Card Plus: It shows you the flow of energy in your house, including the charging power to the car.

   <img src="https://github.com/top-gun/Tesla-PV-charging/blob/main/pictures/GUI-Power-flow-card.png" width=300>

   My definition. As always, you may need to adjust sensor entities if your PV is from a different brand:

type: custom:power-flow-card-plus entities: battery: entity: sensor.battery_charge_discharge_power state_of_charge: sensor.battery_state_of_capacity invert_state: true grid: entity: sensor.power_meter_active_power invert_state: true solar: entity: sensor.inverter_input_power display_zero_state: true individual:

entity: sensor.tesla_charger_power display_zero: true name: Tesla icon: mdi:car clickable_entities: true display_zero_lines: true use_new_flow_rate_model: true w_decimals: 0 kw_decimals: 1 min_flow_rate: 0.75 max_flow_rate: 6 max_expected_power: 2000 min_expected_power: 0.01 watt_threshold: 1000 transparency_zero_lines: 0
```
5.2 Mini-Graph-Card: It shows a graph with the car's SOC and the charging power over the last six hours (adjustable).
```

My configuration:

type: custom:mini-graph-card
entities:
  - entity: sensor.tesla_battery
  - entity: sensor.tesla_charger_power
    name: Tesla Charge Power
    y_axis: secondary
    show_state: true
hours_to_show: 6
points_per_hour: 30
upper_bound: 100
lower_bound: 0
upper_bound_secondary: 11
smoothing: false
extrema: true

5.3 Current Tesla Status: This is a regular card of the type "entities".

The definition:

type: entities entities:

entity: binary_sensor.tesla_charging
entity: binary_sensor.tesla_charger name: Tesla Ladekabel
entity: sensor.autocharge_optimal
entity: sensor.tesla_charger_power
entity: switch.tesla_polling name: Allow Tesla polling
entity: button.tesla_force_data_update state_color: true show_header_toggle: false title: Tesla Status

5.4 Tesla control: Information about the charging process, also switches that change to manual charge control (app) or express charging.

type: conditional
conditions:
  - condition: state
    entity: binary_sensor.tesla_charger
    state: 'on'
card:
  type: entities
  entities:
    - entity: input_boolean.auto_manuell
      name: Manual control
    - type: conditional
      conditions:
        - entity: input_boolean.auto_manuell
          state: 'off'
      row:
        entity: input_boolean.tesla_express
        name: Express Mode
    - type: conditional
      conditions:
        - entity: input_boolean.auto_manuell
          state: 'on'
      row:
        entity: switch.tesla_charger
    - type: conditional
      conditions:
        - entity: input_boolean.auto_manuell
          state: 'on'
      row:
        entity: number.tesla_charging_amps
        name: Charge Amps
    - type: conditional
      conditions:
        - entity: input_boolean.auto_manuell
          state: 'off'
        - entity: input_boolean.tesla_express
          state: 'off'
      row:
        entity: input_number.num_battery_min_home
    - entity: number.tesla_charge_limit
      name: Charge Limit
    - type: conditional
      conditions:
        - entity: switch.tesla_charger
          state: 'on'
      row:
        entity: sensor.tesla_time_charge_complete
        name: Charge complete
  show_header_toggle: false
  state_color: true
  title: Charge Control

top-gun / Tesla-PV-charging

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