Solar heating controller

Hardware

• Inverter: Growatt SPH 8000TL3 BH-UP connected to Server via Growatt ShineWifi-X
• Shelly relay or plug to switch the load, HTTP API enabled
  • For Gen1 devices basic auth is supported, for Gen2+ devices digest auth must be used. This can be changed in the configuration
• Load: Generic heating element, connected to shelly via external load contactor
• Raspberry Pi Zero W to run the software on

Software

• The software retrieves the current battery capacity from the Growatt server
• The software is able to switch a load using shelly HTTP API
• The software switches the load on when the battery percentage is equal to or above a configurable threshold
• The load is switched off again when the battey percentage drops under or is equal to another threshold
• When the server is not reachable for a certain time frame or the system crashes completely, the load is switched off for safety reasons
  • This is realized by sending a one-shot timer to the shelly with a configurable amount of seconds
• The load is always switched off at nighttime (configurable time frame)

Configuration

Example conf/config.ini:

[growatt]
server_url = https://server.growatt.com/
;server_url = https://openapi.growatt.com/
username = user
password = secret123$
inverter_sn = TPXXXXXXXX
login_tries = 3
login_retry_wait_seconds = 10

[shelly]
baseurl = http://192.168.x.x
;'basic for Gen 1 or 'digest' for Gen 2+ Shelly devices
auth_type = digest
username = admin
password = secret123$
turnon_seconds = 1800

[main]
check_interval_seconds = 300
battery_threshold_on_percent = 75
battery_threshold_off_percent = 25
night_start_hour = 22
night_start_minute = 00
night_end_hour = 5
night_end_minute = 00