Everything about installing a Growatt backup box

When the grid fails, you want certainty. With the Growatt backup box, you ensure a reliable backup solution in your PV installation. In this article, you will find everything about installing the Growatt SYN50-XH and SYN100-XH-30 backup boxes, including required components, communication diagrams, software configuration, and useful installation tips.

Why a backup box?

The demand for emergency power supply is increasing. Grid failures are becoming more frequent, which increases the need for a well-functioning backup system. Growatt offers two ways to achieve this within its portfolio:

• Via a HU or SPH inverter with built-in backup function

• Or via a Growatt inverter combined with a separate backup box

In this article, we focus on installing a separate backup box.

What do you need?

For a correct installation of the backup box, you need the following:

- A Growatt battery system, APX or AXE 5.0L-C1 for the white HU inverter

- One of the backup boxes listed below:

Bonus: Growatt backup boxes are equipped with circuit breakers (C63), which simplifies the installation process.

Wiring diagram and cabling

When installing a backup box, you have two choices: full or partial backup.

Note: the power in backup mode is limited by the weakest link — whether that is the inverter or battery. Even if you connect the entire house, it does not automatically mean the full power will be delivered.

Internal layout SYN box

From left to right:

Grid | Bypass | Inverter | Load 

Communication:

For correct operation, both the smart meter and the backup box must communicate with the inverter. This is done via an Ethernet cable. Pay attention to the cable type (depending on environmental interference).

Communication per model:

• SYN50-XH → directly to Min-XH inverter, no smart meter required. 

• SYN100-XH-30 → Both smart meter and backup box separately to MOD/MID XH series

Full backup: 

Partial backup:

Circuit breaker* 

• Typically, installations are done with a residual current device (RCD)/residual current circuit breaker. It is advisable to place this on the line of the inverter before it is connected to the backup box.

Inside the SYN100 box

Communication connection:

SYN50 - to Min-XH inverter: 

SYN50 - to Min-XH2 inverter: 

• Since the energy meter is already built into the SYN50, the single-phase backup box, you only need to connect an RJ45 connector from the backup box for Modbus communication to the "Meter" connection on the inverter, not the "Backup box" connection. Make an RJ45 connector and wire as follows:

  Pin 4: Modbus B 

  Pin 5: Modbus A

Syn100:

MOD series: 

MID series:

Software configuration

The backup box must be correctly activated in the software. This can be done in three ways:

1. Via the ShineTools App

1. Select: ShineWifi S/X

2. Choose the product type: MOD/MID TL3-XH

3. Go to System Settings

4. Turn on “Backup Box Enable”

   • Android: press “Read”

   • iOS: scroll down

5. “Off-grid Enable” is activated automatically

Need a password? Use: growattYYYYMMDD (e.g., growatt20251103)

2. Via the display on the inverter

Follow these steps to activate backup functionality:

1. Go to General Advanced → double tap

2. Enter password 123 → double tap

3. Tap through to “Backup Setting Disable”

4. Select and activate: “Backup Setting Enable”

5. Select: “Backup Box Enable”

6. Confirm settings with “Set OK”

Tip: use single and double taps as indicated. Three taps will take you back to the previous menu.

What a tap on the screen does:

• Single touch (one tap): switch display or increase a number by +1.

• Double touch (double tap): enter or confirm.

• Three touch (three taps): go to the previous menu.

• Hold 5s (hold for 5 seconds): confirm Country/Area or restore default value.

3. Via the online OSS portal (oss.growatt.com)

1. Log in with an installer account

2. Go to: Monitoring & Management > Device List

3. Find the correct inverter (via SN or list)

4. Click on the gear (Operate) on the right

5. Under “Off-grid Function Setting”, set the “Backup” setting to Enable

   1. Note: The values displayed always show the default values; after pressing Yes, these are sent to the inverter. To see what is currently on the inverter, you can use the read button at the top. 

6. Click Yes to send the settings

Common issues

If there are communication problems between the SYN box and the inverter, the following error codes may appear:

If you cannot resolve it despite correct cabling, a software update may be necessary via USB stick on the backup box or updating the inverter/battery. Note the serial numbers of the components and contact us.

📧 Email: support@4blue.nl
📞 Phone: 024 204 2090

Installation tip 

Ensure that circuits are powered exclusively from one point.
➡️ The critical load is therefore not also connected separately from the main connection, but only via the backup box.

Want to know more?

Would you like to know which system best suits your installation? Or are you looking for more information about power limitations, battery types, or Growatt compatibility? Then also check these articles:

🔗 What do I need for a Growatt APX storage system?
🔗 Growatt WIT 4-15K + AXE LV battery

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