How to Assemble the Seplos Mason 280L DIY Battery Kit

Parks List：

1. Wiring cable	2. Cell(purchase separately)	3. Battery box with top cover	4. Wheel
5. Epoxy board	6. EVA foam	7. PC gasket	8. Busbars
9. PCB board	10. PCB board bracket	11. Fuse	12. LCD screen
13. Active balance board	14. 16S200A BMS	15. Middle plate	16. Front panel
17. Balance board plate	18. BMS board plate

 

Screws：

NO.	Specifications	Quantity	Application
1	M3x8mm	3pcs	Fix BMS
2	M6x14mm	18pcs	Fix wheel
3	M4x10mm	9pcs	Fix the connector and the box
4	M4X8mm	5pcs	Fix the PCB board
5	M5x8mm	5pcs	Fix the PCB board bracket
6	M6 flange	32pcs	Connected cell in series
7	M8X20mm	6pcs	Fix the front panel
8	M8X35mm	4pcs	Fix the middle plate
9	M4X10mm	31pcs	Fix cover
10	M8X16mm	4pcs	Fix the connector and fuse

Wire:

NO.	Type	Application
1	Light/comm	Light board and communication board to BMS
2	LCD	Screen to BMS
3	Comm	Communication board to BMS
4	PCB-A1/PCB-B1	PCB board A/B to BMS
5	NO/OFF	Switch to BMS
6	P+	Battery positive to BMS (BMS power supply)
7	Switch	Switch to a balance board
8	BMS-ABB	BMS to balance board (communication)
9	B+/B-	Battery positive/negative to balance board(balance board power supply)
10	PCB-A2/PCB-B2	PCB board A/B to the balance board

Bus Bar:

1. Wheel installation

Install the four wheels in corresponding positions using M6X14mm screws.

2. Cell Placement

Step 1: Test the battery cell (Recommend: Voltage difference is within 0.010V, and the internal resistance difference is: 0.15mΩ)

Step 2: Paste Epoxy boards of corresponding size inside the box.

Step 3: Paste the tested cell with EVA foam and PC gasket at the corresponding cell position.

Step 4:Place the eight cells into the box.

Step 5:Fix with a middle plate with M8X35mm screws. (Don’t forget to place Epoxy board on both side of Middle plate.)

Step 6: Place the other eight cells into the box as well. (Don’t forget to place an Epoxy board in the end. )

Step 7: Fix the cells with the front panel with M8X20mm screws.

3. Cell Connection

Install the Aluminum bus bars to connect cells in series.

4. PCB board bracket installation

Step 1:Attach the EVA foam onto PCB board bracket. (Pay attention to align the holes when pasting.)

Step 2:Install the PCB board onto bracket, and fix with M4X8mm screws.

Step 3: Install the integrated bracket onto the battery box, paying attention to the position of PS-A/B board. and fix with M5x8mm screws.

Step 4: Connect each connectors onto cell terminals. And fix with flange nuts. (Leave P+ and P- for BMS connection.)

5. BMS board installation

Step 1:Install the BMS onto the BMS plate. And secure with M3x8mm screws

Step 2:Install the YS-6/YS-8 copper bus bar on the BMS. And fix with screws.

Step 3: BMS cable connection. Insert the corresponding cable to the BMS.

Step 4: Install the BMS board plate onto battery box. And fix with screws.

6. Balance board installation

Step 1:Attached a thermal pad to the balance board.

Step 2:Install the balance board , communication board, balance switch and P+/P- terminals to the balance board plate. (Don’t forget to fix the screws in the middle of each battery terminal.)

Step 3: Install fuse, copper bus bar YS-4 and YS-7.

Step 4: Insert the corresponding cable to balance board.

7. Balance board installation

Step 1: Install the balance board plate onto battery box, and fix with screws.

Step 2: Insert the PCB-A1/PCB-B1, PCB-A2/PCB-B2 with PCB board. Connect bus bar YS-4/YS-6 with B+/B-. And connect BMS B+ with P+ using P+ cable.

8. Top cover installation

Step 1: Install light board, LCD screen onto the cover. And fix with screws.

Step 2: Insert LCD cable and light board cable.

Step 3: Get the top cover in the position. Pay attention to all the cables.

Step 4: Attach LCD sticker and install the button cap.

Step 5:Fix top cover with screws. Then we finished MASON-280L assembly.

9. Battery pack setup

Please follow other instructions to setup the battery packs with inverters, and to connect battery pack with windows or Bluetooth software.

Congratulations — your Seplos Mason 280L DIY Battery Kit assembly is now complete.

By following the installation steps above, you have successfully assembled a high-performance lithium battery pack with integrated BMS and active balancing system. Proper assembly and correct wiring are essential for achieving long-term safety, stable communication with inverters, and optimal battery performance.

For the best user experience, remember to complete the initial full charge and full discharge cycle so the BMS can accurately learn the battery capacity and calibrate SOC data correctly.

The Seplos Mason 280L is engineered to provide flexible, scalable, and reliable energy storage for residential and commercial solar applications. Whether you are building an off-grid system, home backup solution, or expanding an existing ESS setup, the Mason series offers a professional DIY battery solution trusted by installers worldwide.

If you need further support regarding inverter compatibility, software setup, or battery configuration, please contact the Seplos team for technical assistance and updated documentation.

1. It is very important and necessary to read the user manual carefully (in the accessories) before installing or using battery. Failure to do so or to follow any of the instructions or warnings in this document can result in electrical shock, serious injury, or death, or can damage battery, potentially rendering it inoperable.

2. If the battery is stored for long time, it is required to charge it every six months, and the SOC should be no less than 90%.

3. Battery needs to be recharged within 12 hours, after fully discharged.

4. Do not expose cable outside.

5. All the battery terminals must be disconnected for maintenance.

6. Please contact the supplier within 24 hours if there is something abnormal.

7. Do not use cleaning solvents to clean battery.

8. Do not expose battery to flammable or harsh chemicals or vapors.

9. Do not paint any part of battery, include any internal or external components.

10. Do not connect battery with PV solar wiring directly.

11. Any foreign object is prohibited to insert into any part of battery.

12. The warranty claims are excluded for direct or indirect damage due to items above.