Marstek Jupiter C Plus Battery Storage (battery)
The Marstek Jupiter C Plus is an all-in-one balcony battery storage system with an integrated microinverter, designed for plug-and-play solar self-consumption in residential and small commercial settings. This Modbus RTU template reads battery state of charge and per-channel MPPT power across five input registers (power_a through power_e), giving you live visibility into each solar input string and overall storage level. Connecting the ModbusCloud Gateway to the Jupiter C Plus RS485 port lets you log, trend, and alert on battery and PV data without relying on the Marstek cloud app.
- Protocol
- Modbus RTU
- Connection
- RS485
- Registers
- 6, read only
- Brand
- Marstek
- Last updated
Registers (6)
6 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| soc | % | Read | |||
| power_a | W | Read | |||
| power_b | W | Read | |||
| power_c | W | Read | |||
| power_d | W | Read | |||
| power_e | W | Read |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor battery state of charge continuously to detect degradation or unexpected overnight discharge patterns.
- Track per-MPPT channel power to verify each solar panel string is producing at expected levels.
- Alert on any MPPT channel dropping to zero during daylight hours to catch shading, wiring, or panel faults early.
- Compare power_a through power_e values across multiple Jupiter C Plus units on one site for performance benchmarking.
- Report daily PV yield per channel to building owners as evidence for system performance reviews.
Installation
Locate the 5-pin RS485 port on the rear of the Marstek Jupiter C Plus. Obtain a compatible Weipu SP17 5-pin connector and wire pin 1 (A+) and pin 2 (B-) to the A and B terminals of the ModbusCloud Gateway RS485 interface.
Connect the ModbusCloud Gateway to the same RS485 bus. Set the adapter baud rate to 9600, 8N1 (or the rate documented for your firmware version) in the Gateway communication settings.
In the ModbusCloud portal, add a new Gateway, then import the Marstek Jupiter C Plus Battery Storage template. Assign the correct Modbus unit ID (slave address) matching the device configuration, typically 1.
In the portal live-data view, verify that the soc register returns a value between 0 and 100 and that at least one power channel shows a non-zero reading during daylight. If all channels read zero, recheck wiring polarity on pins 1 and 2.
Things to watch for
All power channel registers read zero even in sunlight. Why?
Check RS485 wiring polarity first: A+ must connect to pin 1 and B- to pin 2 on the Jupiter C Plus RS485 socket. A reversed connection returns no data. Also confirm the unit is powered on and actively charging or discharging, as the device may suppress output during standby.
The SOC register reads an implausible value. What is wrong?
The soc register is uint16 with no scaling factor defined in the template. The raw register value should equal the percentage directly. If the value exceeds 100, suspect a unit ID mismatch: you may be polling the wrong device on the bus. Confirm the Modbus slave address set on the Jupiter C Plus matches the unit ID in the portal.
Only some MPPT channels show data. Others are stuck at zero.
The Jupiter C Plus has four physical MPPT inputs (PV1 to PV4). If fewer than four panels are connected, unused MPPT channels will legitimately report zero. Cross-check how many panels are physically wired to the unit before treating a zero reading as a fault.
The Gateway connects but register reads time out intermittently.
The Jupiter C Plus RS485 interface does not supply power to external adapters on the Jupiter C Plus variant (pin 3 is inactive). Ensure the RS485-to-serial adapter has its own power supply. Also note that only one Modbus master can communicate at a time: if another device (such as a Home Assistant integration) is polling simultaneously, requests will collide and cause timeouts.
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