Home Assistant Inverter Charge Control

Dynamic inverter grid charge current adjustment automation for Home Assistant, designed to handle weak/unstable grid conditions by intelligently adjusting charge rates based on real-time voltage monitoring.

Overview

This automation dynamically adjusts the inverter's maximum grid charging current based on grid voltage conditions. It enables safe charging from weak grids by reducing charge current when voltage drops, and maximizing charge rate when grid conditions improve.

Goals

• Maintain grid connection during weak/unstable grid conditions
• Maximize charging efficiency when grid is stable
• Protect inverter EEPROM by limiting write operations
• Prevent grid overload by estimating voltage drop under different charge rates
• Automated operation requiring minimal manual intervention

Problem Statement

In areas with weak or unstable grid infrastructure, high charge currents can cause voltage drops that trigger inverter protection mechanisms, disconnecting the grid when charging is most needed. Manual adjustment is impractical, and conservative fixed settings waste charging opportunities when grid conditions are good.

Solution

The automation continuously monitors grid voltage (current, minimum, and average over 15 minutes) and dynamically adjusts the battery charge current between 5A and 30A based on:

1. Current grid state - Whether grid is available or unavailable
2. Voltage measurements - Real-time voltage, 15-minute minimum, and 15-minute average
3. Power consumption - Current grid power draw (house load + charging)
4. Projected voltage impact - Estimated voltage drop if charge current is increased
5. Battery state - Current charge level to avoid unnecessary EEPROM writes when nearly full

Key Logic

The automation estimates future voltage conditions using:

• Current state estimation: Uses actual grid power (house load + charging) to understand current voltage drop
• Future state projection: Estimates voltage drop for proposed charge current using:

  House load (estimated 500W) + (Charge current × Battery voltage 48V)
  

• Voltage drop model: Approximately 5V drop per 1kW of power draw
• Safety margin: Uses the minimum of current voltage and 15-minute minimum voltage to ensure conservative decisions

The automation will only increase charge current if the projected voltage remains above 195V threshold.

Requirements

Hardware

• Inverter: Deye SUN-6K-SG03LP1-EU (logic should work with other inverters with adjustable parameters)
• Battery system: 48V battery bank
• Grid connection: Single phase (currently monitors L1)

Software

• Home Assistant: Version 2026.1.1 or later
• Integration: Solarman Stick Logger for reading/writing inverter parameters

Required Home Assistant Entities

The following entities must be available from your inverter integration:

Entity ID	Description	Type
binary_sensor.inverter_grid	Grid availability status	Binary Sensor
sensor.inverter_grid_l1_voltage	Real-time grid voltage (L1)	Sensor (V)
sensor.inverter_grid_l1_power	Real-time grid power draw	Sensor (W)
sensor.inverter_battery	Battery state of charge	Sensor (%)
number.inverter_battery_grid_charging_current	Grid charge current setting	Number (A)

Note: Adjust entity IDs in the configuration files to match your actual integration's entity names.

Configuration Details

Statistics Sensors (configuration.yaml)

Two statistics sensors track voltage behavior over 15 minutes:

- platform: statistics
  name: inverter_grid_l1_voltage_stats_min_15m
  entity_id: sensor.inverter_grid_l1_voltage
  state_characteristic: value_min
  max_age:
    minutes: 15

- platform: statistics
  name: inverter_grid_l1_voltage_stats_avg_15m
  entity_id: sensor.inverter_grid_l1_voltage
  state_characteristic: mean
  max_age:
    minutes: 15

These provide:

• Minimum voltage over last 15 minutes (worst case scenario)
• Average voltage over last 15 minutes (typical conditions)

Write Budget Counter

Protects inverter EEPROM by limiting write frequency:

counter:
  grid_charge_writes_30m:
    name: Grid charge writes (30m)
    initial: 0
    step: 1
    minimum: 0
    maximum: 100

Budget limit: 6 writes per 30 minutes (configurable via write_budget_30m variable)

Automations

1. Grid State Notification

Sends mobile notification when grid connects or disconnects, including voltage and battery level.

2. Grid Charge Write Budget Reset

Resets the write counter every 30 minutes to maintain the write budget window.

3. Grid Charge Write Budget Notification

Alerts when write budget is exceeded (more than 3 writes in 30 minutes).

4. Battery Grid Charge Current Adjustment (Main Automation)

Triggers:

• Grid state change (on/off)
• Voltage drops below 190V
• Time pattern (every 5 minutes)

Decision Logic:

Condition	Action	Charge Current
Grid off OR voltage ≤190V	Emergency: Set to minimum	5A
Battery ≥95%	No change	Current
Projected voltage @ 30A ≥195V	Increase to maximum	30A
Projected voltage @ 20A ≥195V	Increase to medium-high	20A
Projected voltage @ 10A ≥195V	Increase to medium	10A
None of above	No change	Current

EEPROM Protection:

• Minimum write interval: 900 seconds (15 minutes) between changes
• Write budget: Maximum 6 writes per 30 minutes
• Change detection: Only writes when value actually changes
• Budget tracking: All writes are counted and budget enforced

EEPROM Life: Deye inverters have a minimum 1 million write cycle limit. In worst case scenario this automation may write up to 8 times per hour, resulting in over 11 years of operation before reaching this limit. However, the actual write frequency is typically much lower due to stable periods (when grid is off, when grid is on and stable, or when battery is charged).

Inverter Settings

The following inverter settings have been tested and work well with this automation:

Parameter	Value	Purpose
Grid Reconnect Time	10 minutes	Allow grid to stabilize before reconnecting
V Low (Normal)	185V	Low voltage protection threshold
LV1	187V	Level 1 low voltage protection

These settings provide appropriate protection while allowing the automation to manage charging dynamically.

Tuning Parameters

Key variables in the main automation that can be tuned for your setup:

variables:
  write_budget_30m: 6              # Maximum writes per 30 minutes
  min_write_interval_secs: 900     # Minimum seconds between writes
  house_load_est: 500              # Estimated house load in watts
  dv_per_kw: 5                     # Voltage drop per kW (5V/kW)

Contributing

Contributions are welcome! If you improve this automation or adapt it for other inverter types, please share your changes.

License

See LICENSE file for details.

Acknowledgments

• Home Assistant community for the excellent home automation platform
• Solarman integration developers for enabling inverter communication
• Users dealing with weak grid infrastructure who inspired this solution