General understanding of device cabling

[MartFrie]

Hello, I have a problem in understanding of the cabling of the devices. Please can you help me to understand the basics?
Unfortunately, I'm not very familiar with Modbus/CAN communication.

My problem is as following:
I have a problem: I have two Meritsun battery packs on my Deye inverter and would like to expand them with two Seplos battery packs. I would like to set up communication between the four battery packs and the inverter. For now, I just want to test the existing Meritsun battery packs with this system. If the communication works, I would like to expand the system. Can you please help me understand the wiring of the devices?

Here is the diagram of my system:

Thank you for your help :-)

[ai-republic]

Hey @MartFrie,
welcome and thanks for the great diagram 😉
I need a little bit more information:

1. What communication interface (CAN/RS485) do your Meritsun and Seplos batteries support. If they have CAN interfaces then I would recommend that.
2. What CAN or RS485 hat are you intending to use for you PI (that depends I guess also what interfaces are supported)?

[MartFrie]

Hi and thank you for you quick reply.

1. The Meritsun and Seplos batteries support both CAN and RS485. The Deye inverter requires CAN for communication, while the battery packs communicate via RS485 (Master / Slave - mode).

2. I have a Waveshare CAN Hat for Raspberry Pi 1CH CAN Hat (https://www.waveshare.com/product/rs485-can-hat.htm).

Detailed infomration about battery BMS types:
MERITSUN
For two or more battery packs, Meritsun uses RS485 communication between the batteries. The batteries are addressed via a 4-bit DIP switch.

SEPLOS
Seplos BMS offers truly "interesting" communication between multiple battery packs.
It features an 8-bit DIP switch for addressing. Switches 1–4 are for RS485 addressing, and switches 5–8 are for CAN addressing.

[ai-republic]

Ok great, so I guess there's only one option with your current setup and testing first only with the 2 Meritsun packs.
You'll need to connect the 2 Meritsun packs via RS485 and the inverter via CAN:

• chain them like in your initial diagram with the respective DIP switch configuration
• connect the master (id 1) to the PI's RS485 hat A/B port (usually RJ45 pin 1&2 and/or 7&8)
• connect the inverter via CAN to the PI's RS485 hat H/L port (usually RJ45 pin 4 & 5)

Please refer to the documentation for the exact RJ45 pin layout!

For your final setup I would recommand using the 2CH-CAN hat though and use CAN throughout your setup. This will even give you the option to stack your existing RS485/CAN hat on top and later address other BMSes too (just a thought 😉 ).

[ciechomir]

I have a similar question.
I’m using a CAN HAT on a Raspberry Pi, like the one in the photo.
I have two different batteries communicating via CAN, and I want to connect them to a Deye inverter.
How should I connect the cables? Do I need a different converter, or can I connect everything to the Waveshare module?

Does the inverter have to be connected to one CAN port, and both batteries to the other?

[ai-republic]

Yes, the latter. You need to connect the BMSes to one CAN port (e.g. can0) and the inverter to another (e.g. can1). This works if your BMSes speak the same protocol, e.g. Pylon. If you BMSes speak different protocols then you need possibly a third CAN port (can3)

[ErikssonPer]

https://www.mydhli.com/global-en/home/tracking.html?tracking-id=1735737485&submit=1

…

On Fri, Apr 18, 2025 at 9:39 AM Torsten Oltmanns ***@***.***> wrote: Yes, the latter. You need to connect the BMSes to one CAN port (e.g. can0) and the inverter to another (e.g. can1). This works if your BMSes speak the same protocol, e.g. Pylon. If you BMSes speak different protocols then you need possibly a third CAN port (can3) — Reply to this email directly, view it on GitHub <#120 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/A6KRUROV22L5BED22JFGNQL22CT37AVCNFSM6AAAAAB3HYMBGCVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTEOBXGU2DMOA> . You are receiving this because you are subscribed to this thread.Message ID: <ai-republic/bms-to-inverter/repo-discussions/120/comments/12875468@ github.com>

[MartFrie]

@ ai-republic
Thank you for your reply. I think I understand what you mean.
I'll test the system as soon as possible. :-)
I also ordered a 2-channel CAN hat for this project. Thanks for the tip about the stackable CAN hat. I think it's a very good solution for my project.

I tried to create something like a block diagram to better understand the system structure. Did you mean the system wiring as follows?