# \[APP\]\[Pro\] SAJ - HS3 Modbus

**URL:** <https://community.homey.app/t/app-pro-saj-hs3-modbus/160710>\
**Category:** Apps\
**Tags:** app\
**Created:** [October 12, 2026, 8:35am UTC](https://community.homey.app/t/app-pro-saj-hs3-modbus/160710 "2026-10-12T08:35:47Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Dennis\_Berggren](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/dennis_berggren/32/113660_2.png) [@Dennis\_Berggren](https://community.homey.app/u/Dennis_Berggren)\
**Post date:** [October 12, 2026, 8:35am UTC](https://community.homey.app/t/app-pro-saj-hs3-modbus/160710/1 "2026-10-12T08:35:47Z")

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I started to work on an app for connecting to your SAJ HS3 (and most likely H2) over Modbus TCP.  
It is still an early version but please feel free to test and play around. I will try to improve it quickly based on input.

> **[SAJ HS3 Control | Homey](https://homey.app/en-se/app/com.saj.hs3/SAJ-HS3-Control/test/)**
>
> Monitor and control a SAJ HS3 home battery locally over Modbus TCP

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<div class="post-metadata">

**Author:** ![Dennis\_Berggren](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/dennis_berggren/32/113660_2.png) [@Dennis\_Berggren](https://community.homey.app/u/Dennis_Berggren)\
**Post date:** [October 12, 2026, 8:48am UTC](https://community.homey.app/t/app-pro-saj-hs3-modbus/160710/2 "2026-10-12T08:48:31Z")

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Troubleshooting

**Full guide:** [Homey\_SAJ\_HS3/TROUBLESHOOTING.md at main · DennisBerggren/Homey\_SAJ\_HS3 · GitHub](https://github.com/DennisBerggren/Homey_SAJ_HS3/blob/main/TROUBLESHOOTING.md)

**Quick checks if you can’t add the device:**

1. **“No answer” / “timed out”** – Homey can’t reach the inverter.

2. **“Refused the connection”** – wrong port or wrong device. Port should be **502**.

3. **“The inverter closed the Modbus connection”** – the AIO3 module only accepts a limited number of Modbus clients. If **Home Assistant** (SAJ H2 Modbus integration) or another tool is already connected, disable it and try again.

4. **“Did not answer the Modbus request”** – check that Modbus unit id is **1**.

**Control doesn’t work?**

- The app is **read-only by default** → Device settings → Control → Access → _Read and write_.
- If **Tibber Smart control** is on, Tibber overrides all commands. Control only works with Smart control off. Reading always works.

**When reporting a problem** , please include: inverter model + firmware, how it’s connected (AIO3 WiFi/LAN), the exact error message, and the result of the `nc` test.