How to connect Tesla Megapack battery (BESS) with Reduxi Controller
Connect a Tesla Megapack battery storage to the Reduxi Controller via Modbus TCP: enable the protocol on the Megapack, add the device in the Configurator and check the readings.
1 Technical documentation
The Tesla Megapack is a containerised battery energy storage system for commercial, industrial and utility sites. The Reduxi Controller connects to it over the local network with Modbus TCP and reads the battery values (power, state of charge, capacity, energy counters) as well as the grid and PV values that the Megapack reports.
Manufacturer documents:
- Tesla Megapack – product page and general information (EN)
- Megapack Modbus interface register map – on request from the manufacturer (not public)
2 Required equipment
- Reduxi Controller, installed and online
- Tesla Megapack, commissioned, with a network connection (Ethernet) that the Reduxi Controller can reach in the same network
- Access to the Megapack web interface (from the installer or from Tesla) to enable the Modbus TCP/IP protocol
- Laptop or tablet with internet access to configure the device in Reduxi
3 System overview & connection
The Megapack and the Reduxi Controller communicate over the local network. Connect both to the same network (switch or router) and give the Megapack a fixed IP address, so that the address entered in Reduxi does not change.
| Connection | Details |
|---|---|
| Megapack ↔ network | Ethernet cable to the local network (LAN) |
| Reduxi Controller ↔ network | Ethernet or Wi‑Fi to the same network |
| Protocol |
Modbus TCP, port 502, unit ID 1
|
4 Configure the Megapack
Before the Reduxi Controller can read the Megapack, the Modbus TCP/IP client protocol has to be switched on in the Megapack web interface.
4.1 Enable Modbus TCP/IP
502 and Modbus unit ID 1. You enter these values in Point 6.2.5 Log in to the Reduxi web interface
The device is added in the Configurator, the web interface of the Reduxi Controller. You do not add it in the Reduxi app itself or in the Reduxi Cloud. You can open it in two ways:
http://reduxi.local in the browser. You find the IP address in the device list of your router or in the app under Reduxi devices.admin · Password admin (factory default; if it was changed during installation, use that one; this is not your Reduxi account password).admin login is not your Reduxi account. reduxi.local only works in the same network as the controller.6 Add the device to Reduxi
6.1 Basic settings
Tesla Megapack, and click Next.6.2 Communication settings
| Parameter | Value |
|---|---|
| Connection | TCP/IP |
| IP | IP address of the Megapack (see Point 3) |
| Port | 502 |
| Modbus unit ID | 1 |
| Extended IP recovery | On (recommended: finds the device again if its IP address changes) |
6.3 Optional settings
These settings sit in the device details and depend on your installation:
| Setting | Meaning |
|---|---|
| Limit communication with the device to read-only | On: Reduxi only reads values and does not send any setpoints to the Megapack. Use this when the Megapack is operated by its own controller or by another energy management system. |
| Battery capacity | Usable capacity of your Megapack installation in kWh. |
| Device timeout | Time after which the device is reported as not reachable. 60 s is a good starting value. |
| Is PV installed / Is meter installed | Switch on only if the Megapack site controller reports PV or grid meter values that Reduxi should use. |
6.4 Test communication
Click Test communication at the bottom of the wizard. It reads the device once and saves nothing. If the test is successful, click Done. Only Done creates the device.
A successful test shows Successful readout from device and the values read. If the port or the address is wrong, the test shows Unable to communicate with device and the reason:
7 Check the readings
7.1 Check the readings
Open Devices → your Megapack → Last measurements. The values update every few seconds.
| Value | What you see |
|---|---|
| Battery – Active power | Current charge or discharge power in kW |
| Battery – Max / min active power | Charge and discharge power limits reported by the Megapack |
| Battery – State | Operating state, for example STANDBY
|
| Battery – State of charge | Current state of charge in %, with the minimum and maximum limits |
| Battery – Capacity / max capacity | Available and maximum energy in kWh |
| Battery – Import / export active energy | Energy counters in kWh |
| PV, Inverter, Grid | Values the Megapack site controller reports for the connected PV, inverter and grid meter |
7.2 Control behaviour
If read-only is switched on (see Point 6.3), Reduxi uses the Megapack as a measuring device and does not control it. Without read-only, the Megapack can be included as a regulated device in the strategies of the Reduxi Controller (see the related article about strategies).
✓ Summary
Preparation (Points 1–3): Megapack and Reduxi Controller are in the same network, the Megapack has a fixed IP address.
Megapack (Point 4): In the Megapack web interface, enable Modbus TCP/IP under Client Protocols.
Add to Reduxi (Points 5–6): Open the Configurator, add a Battery device, enter the IP address, port 502 and unit ID 1, run Test communication and click Done.
Go live (Point 7): Check the last measurements and the charging direction; use read-only if the Megapack is controlled by another system.
→ Common issues
| Issue | Solution |
|---|---|
| Test communication fails, no values from the Megapack | Check that Modbus TCP/IP is ticked under Client Protocols on the Megapack, that the IP address is correct and reachable from the controller, and that port 502 and unit ID 1 are entered. |
| The device shows values, but nothing is controlled | Read-only mode is switched on. Switch it off in the device details if Reduxi should control the Megapack. |
| Charging and discharging appear the wrong way round | Compare with the Megapack display and contact Reduxi support. |
| Open configurator does not open or stays empty | The tunnel is not active yet. Wait about 30 seconds and check that the controller is online. |
| Login with admin is rejected | The password was changed during installation. Ask the installer. The Reduxi account password does not work there. |
| reduxi.local does not load | You are not in the same network as the controller. Use the IP address or the tunnel. |
| Communication test fails, device offline | Check reachability, IP address, port and unit ID, and that the protocol is enabled on the device. |