Integrate SmartShunt or Shelly Uni to read SOC

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I installed my 24V Battery System together with an HM300 and so far the system works as expected. I am using a PowerQueen 24V LiFePO Battery which has an BMS, however that's not accessible.

Hence, I bought a Shelly UNI which can read the Battery voltage. At the moment I am using Homeassistant and the shelly integration to read the SOC and to do stuff based on the SOC.

This afternoon I stumbled upon the Shelly API and what I understood so far is that the SOC can also be read through HTTP GET.

Hence my question: Could this also be implemented in on-Battery, basically like it has been done for the Huawei PSU? The shelly is really cheap and I think the ability to use it as a SOC transmitter for this project could help to make it more versatile and "compatible" with standard batteries which do not provide an extensive BMS.

Any thoughts?

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a command "http://IP/status/" provides following output:

{"wifi_sta":{"connected":true,"ssid":"xxxxxx","ip":"xxxxxxxxxxx","rssi":-83},"cloud":{"enabled":true,"connected":true},"mqtt":{"connected":false},"time":"08:12","unixtime":1682403163,"serial":7057,"has_update":false,"mac":"xxxxxxxxxxxx","cfg_changed_cnt":2,"actions_stats":{"skipped":0},"relays":[{"ison":false,"has_timer":false,"timer_started":0,"timer_duration":0,"timer_remaining":0,"source":"input"},{"ison":false,"has_timer":false,"timer_started":0,"timer_duration":0,"timer_remaining":0,"source":"input"}],"inputs":[{"input":0,"event":"","event_cnt":0},{"input":0,"event":"","event_cnt":0}],"adcs":[{"voltage":26.18}],"ext_sensors":{},"ext_temperature":{},"ext_humidity":{},"update":{"status":"idle","has_update":false,"new_version":"20221027-121732/v1.12.1-ga9117d3","old_version":"20221027-121732/v1.12.1-ga9117d3","beta_version":"20230329-163727/v1.13.0-rc2-g1b3e5af"},"ram_total":50784,"ram_free":37432,"fs_size":233681,"fs_free":146835,"uptime":56801}

In addition, reading the battery and other temperatures would also be possible by connecting sensors to the UNI, which is is pretty simple.

[swingstate]

Same topic, but different approach - the victron smart shunts also provide a VE.Direct port to read the battery data. Maybe this would be easier, since there is also support for viltron MPPTs implemented. And maybe less extra code?

I am going to test a SmartShunt 500 A connected to a Wemos Mini (Using the VE. Direct port) and integrate it into Homeassistant to compare the accuracy of the SOC measurement with the Shelly UNI and a DC Relay PCB I bought on eBay. The Uni reads to low ( -0,6V, which can be adjusted in the UNI webgui), the DC Relay PCB to high (+ 0.2V, no adjustment possible on the board)

Generally speaking I think it would be beneficial to implement a more universal SOC reading capability through either the UNI or a smart shunt into onBattery, to make it more universal and the solutions based on it more failsafe.

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plus, not having to rely on another system (in my use case homeassistant) to measure the SOC and to react to it could make the whole approach of solar + energy storage simpler/more failsafe.

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Smartshunt is installed and connected to an ESP8266 which is connected to Homeassistant.

The amount & quality of information this combination provides is amazing and the level of accuracy is unmatched. The Shelly is a relatively cheap (20€) solution to read the SOC, however the UNI needs to be configured with an offset of +0.65V to get close to what I measure with a multimeter or now with the Shunt.

Biggest difference in measurement quality is also that the Shelly sways up and down 0,05 - 0,1V, where the shunt just provides a stable read.

the purple line is the shunt, the other the Shelly when switch from rest to discharge 150W max.

Given this project is victron centred I'd suggest to integrate the smartshunts so the DTU can make more accurate decisions when dealing with batteries.

I would still look into adding support for the the Shelly, since it's an okay solution and cheaper but the Shunt provides more accurate data.

[swingstate]

@helgeerbe any idea when you think this could be implemented?

[spcqike]

another possibile solution one could try and implement is a DIY SmartShunt
https://github.com/kscholty/SmartShuntINA226

either as additional device or build into opendtu (like the OLED)

unfortunatly, i dont have a battery (yet). i allready ordered and tested an 100A/75mV shunt, which is very accurate (0.7496 mOhms instead of 0.75 mOhms), i have a INA226 laying around and some ESP8266. but, i dont have a battery nor a solar charger :D

[swingstate]

Well, you could add that feature to a all-in-one PCB which covers a ESP32 for OpenDTU, a Relay for the AC (and maybe DC) disconnect of the inverter (and battery), 3x VE.Direct Ports for MPPTs & a Victron Shunt, 100A DC input, Can Bus, NRF & CMT Radios, INA226 based current reading and 4 - 6 x 12A DC ports with integrated inrush protection for the Inverter. This will probably require a MCP based GPIO extension.

That would be a very universal PCB to enable flexibility & add some safety nets. I working on such a PCB, but that takes time :)
Until then the Victron Shunt does a very good job.

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