esphome-evbox-smartgrid

Caution

Untested and unproven. Use entirely at your own risk.

• This component has never been run on a real EVBox charger. It was written from EVBox's protocol document and community reverse engineering, and has so far only been compiled.
• Nothing in this repository is confirmed to work, to be safe, or to be correct for your charger. That includes the connector and pinout in the installation guide.
• Mistakes can damage the charger, the car or the electrical installation, overload the very connection this is meant to protect, or affect warranty and insurance.
• An EV charger carries mains voltage. Opening it and connecting anything inside is work for a qualified electrician.
• This project is not affiliated with or endorsed by EVBox. There is no support and no warranty; see the disclaimer and the MIT license.

Only use this if you can verify every step yourself and accept the consequences if something goes wrong.

An ESPHome external component that turns an ESP32 into the SmartGrid module of an EVBox G3 charger. It uses the RS-485 interface EVBox documented for third-party devices (Protocol Max v4, command 69) to set the maximum charging current in real time, and reads back the current per phase, the power factor and the charger's energy meter.

The charger's own communication module (the modem and its OCPP backend) stays in place and keeps working. This component adds a local current limit on top of it, controlled by Home Assistant.

Status

Compiles against ESPHome 2026.8.2	checked in CI on every push
Frame format and checksum	checked against the example frame in the EVBox document
Works on a real charger	not tested
Location and pinout of the bus connector on the G3 modem	not verified
Fallback after the timeout	not tested
Pausing below the charger's minimum current	not tested

Why

A 3 × 16 A charger leaves little room on a 3 × 25 A connection. When the oven, the dishwasher and the car all run, a phase goes over the main fuse. Cloud backends can often only start or stop a session. This component is meant to let Home Assistant lower the charging current locally, within seconds, and raise it again when there is room.

How it works

flowchart LR
  HA["Home Assistant"] -- "ESPHome API" --> ESP["ESP32<br/>SmartGrid module (0xA0)"]
  ESP -- "RS-485, command 69" --> CP["ChargePoint module (0x80)<br/>modem + OCPP"]
  CP -- "station bus" --> CB["ChargeBox"]
  CB --> EV["Car"]
  CP -. "cellular" .-> Backend["OCPP backend"]

Loading

According to the EVBox document:

• Every update_interval the component sends command 69: the maximum current for L1, L2 and L3, a timeout, and a fallback current.
• The ChargePoint replies with the current in use per phase, cos φ and the meter reading.
• If the frames stop (ESP32 off, Wi-Fi gone, keep-alive switched off), the ChargePoint applies the fallback current once the timeout expires.
• The limit can only lower the charger's own maximum, never raise it.
• The car may take up to about 10 seconds to follow a new limit.

None of this has been observed on a real charger yet. Protocol details are in docs/protocol.md.

Hardware

• Charger: EVBox BusinessLine or HomeLine G3, with a separate modem board (for example 471046.x UMTS-E with a SIM5320E). The EVBox document also covers G4, but G4 hardware is not covered here.
• ESP32 with a 3.3 V RS-485 transceiver. The example uses an M5Stack AtomS3 Lite with an ATOMIC RS485 Base, which accepts 6–24 V and powers the Atom from it. Transceivers built around a 5 V MAX485 are reported not to work with 3.3 V microcontrollers. If your transceiver needs a direction pin, set flow_control_pin on the uart:.

Wiring, pin identification and commissioning are in docs/installation.md. Read its warnings first.

Configuration

external_components:
  - source: github://tmisker/esphome-evbox-smartgrid
    components: [evbox_smartgrid]

uart:
  id: evbox_bus
  tx_pin: GPIO6
  rx_pin: GPIO5
  baud_rate: 38400

evbox_smartgrid:
  id: evbox
  update_interval: 15s
  timeout: 60s
  fallback_current: 16

number:
  - platform: template
    name: Max charging current
    optimistic: true
    min_value: 0
    max_value: 16
    step: 1
    initial_value: 16
    restore_value: true
    unit_of_measurement: A
    on_value:
      - lambda: id(evbox).set_max_current(x);

A complete device configuration is in example/evbox-smartgrid.yaml.

evbox_smartgrid

Option	Default	Description
uart_id		UART bus, 38400 baud, 8N1.
update_interval	15s	How often command 69 is repeated. Frames are never sent more often than the minimum interval the ChargePoint reports.
timeout	60s	Sent to the ChargePoint. Without a frame for this long, it should switch to fallback_current. Must be at least twice update_interval.
max_current	16	Initial maximum current per phase, in A.
fallback_current	16	Current per phase the ChargePoint should apply when the frames stop, in A.

Methods for lambdas:

Method	Description
set_max_current(float amps)	New limit per phase. Sent right away when it changes. Values below the charger's minimum (usually 6 A) are expected, but not confirmed, to pause charging.
set_keepalive_enabled(bool)	Stop or resume sending. When stopped, the ChargePoint should fall back after the timeout.
get_max_current(), is_keepalive_enabled()	Current settings.

Sensor platform

Key	Unit	Description
current_l1, current_l2, current_l3	A	Current in use per phase.
power_factor_l1, power_factor_l2, power_factor_l3		cos φ per phase.
energy	kWh	Meter reading of the charger.
minimum_current	A	Minimum current the ChargeBox needs to charge.
connection_max_current	A	Maximum current of the connection, as known to the ChargePoint.
minimum_interval	s	Shortest interval between frames the ChargePoint accepts.

With more than one ChargeBox on a ChargePoint, the sensors show the first one.

Binary sensor platform

Key	Description
responding	On while the ChargePoint answers; off after about three missed replies.

Using it from Home Assistant

The limit is an ordinary number entity, so any automation can set it:

action: number.set_value
target:
  entity_id: number.evbox_smartgrid_max_charging_current
data:
  value: 10

Keep the decision logic in Home Assistant, where the whole house's consumption is known. Lower the limit quickly and raise it slowly, so heaters that cycle on and off do not make the charging current jump up and down. Do not rely on this component as your only protection against overloading a connection: the main fuse and the installation's own protection stay essential.

Safety

• The ChargePoint is documented to cap the limit at the connection's maximum, but it trusts the numbers you send. Never set fallback_current or the number's maximum above what the installation, cable and car can handle.
• Only command 69 is sent. The internal station bus between ChargePoint and ChargeBox uses other commands; experimenting with those has bricked a ChargeBox before. Do not connect this component to that bus.
• EVBox has stopped trading. There is no manufacturer support.

Credits

• EVBox for publishing Protocol Max v4 – Third party interface.
• Maarten Tromp (geekabit) for documenting the internal protocol and the G2/G3 hardware.
• ajvdw/evbox and BerndSchrooten/home-assistant-esphome-evbox-controller for earlier ESPHome implementations of command 69.
• sequ3ster/protocol-max for an earlier Arduino library for the same protocol.
• Ricardo Schluter for an ESPHome controller for G2 on the same M5Stack hardware.
• Harm Otten for early reverse engineering of the EVBox bus.

No code from these projects is included.

Disclaimer

This software and its documentation are provided "as is", without warranty of any kind, express or implied. It is an untested prototype. The authors are not liable for any damage to chargers, vehicles, electrical installations, property or persons, or for any other consequence of using it. You alone are responsible for deciding whether to use it, for any modification to your charger, and for complying with local regulations and with the conditions of your warranty and insurance.

License

MIT, see LICENSE. EVBox is a trademark of its owner; this project is not affiliated with EVBox. The EVBox protocol document is not included in this repository.