DALY UART connection

[smejfi]

Hello, I have a question about connecting DALY smart bms with uart. Im using original VE direct to USB cable and I cant get Venus os to see the bms although when I connect it to PC (with the same cable) and use the BMS Monitor sw from Daly, it works perfectly. Also, when I use Daly RS485 to USB cable, it works well and I can see it in Venus OS. Would you please have some advise what could be the problem? The reason why I want to use UART is because eventualy I need to use different bms which uses xiaoxiang app and has only UART port. I tried that one first and it didnt work so I figured I would try it with daly bms (which I know is working at least with RS485) so I would find out if the problem is in the bms or somewhere else and for now it seems that the problem is not in bms because daly with uart doesnt work either. Thank you for your answer.

[Louisvdw]

Hi @smejfi
There are 3 possible problems that you can check.

1. Make sure the cable you use is compatible with the BMS. The common UART types you get are TTL (sometimes just labled UART), RS232(also sometime just labled UART) and RS485. They each work with different voltages and different protocols. Ve.Direct is TTL cable.
2. The Ve.Direct cable is isolated meaning power cannot flow from the one side to the other. It's a safety feature but it require that you supply power from both sides. The USB side gets power from the USB and you also need to connect the Ground and Positive from the BMS side (normally you will supply 5V).
3. The RX/TX cables can be the wrong way around. It is say to just swop them to see if it will work.

If your Daly has a RS485 cable just use that one.
The UART port on the JBD/LLT BMS is a TTL and the Ve.Direct should work if powered from the BMS side as well.
Also look at the Troubleshoot section in the wiki on which log files you need to look at they will tell you what is happening.

[Louisvdw]

QUCC does not make BMS. They just sell other BMS. So that one that looks like the JBD is a JBD with another label. I have a QUCC labled bms on the bench that I still need to get to, and that is actually an AXEBMS. This is why they work even though QUCC is not on the supported list.

[smejfi]

It is connected to the cells, namely the Daly BMS is connected to 13s li-ion and qucc bms is connected to 4S lifepo4. Actually, I found out that qucc bms uart port has quite large voltage on its VCC pin, I think I measured over 12 V! The first thing I did when the VE direct to USB cable arrived from the shop, I connected it to that qucc UART port (including its VCC pin), so one of my ideas is that I might have damaged that VE direct to USB cable. On the other hand, then I tested it with my MPPT and it was communicating with no issues, so it should be fine...

[Louisvdw]

Then it could be that it is not compatible with the BMS.
It could also just be a loose connection messing up the signals if the fit is not great.

[smejfi]

Maybe, but with Daly BMS I was able to make it work on windows, so the connection and the cable-bms compatibity should be fine...really, I dont know :-D

[rbeudel]

I got my 16S Daly working via UART with a simple FDTI USB converter connected only TX,RX and gnd. I bought a DALY UART cable in a german shop, no function with windows or venus os.