JK-B2A8S20P BMS gps port fried my USB to ttl converter

[Smudgey]

After watching Andy’s video over at the off grid garage about connecting the JK BMS to my raspberry pi. I ordered an isolated usb to ttl converter and followed the instruction. All the connections are correct but my converter went up in smoke. It turns out the voltage coming out of the BMS was 25volts. Can anyone tell me what voltage is coming out of their bms gps port? I am assuming mine is faulty.
The voltage for the tx rx line are 3 ish volts which I assume is correct.

 

[sergea]

always check documentation before acting. don't do like Andy ;-). yep power pin is VBAT need a dc/dc converter if you ant to power your converter from the BMS. serial pins are 5V ttl on the serial port. don't know for the gps port, you have to ask your vendor.

 

[meetyg]

I think you shouldn't have connected the positive wire from the JK to the converter. The converter positive is only compatible for up to 5v, whereas the JK outputs more than that.
Yes it confusing, but it's always wire to check voltages and polarity before connecting anything.

 

[Smudgey]

I think you shouldn't have connected the positive wire from the JK to the converter. The converter positive is only compatible for up to 5v, whereas the JK outputs more than that.
Yes it confusing, but it's always wire to check voltages and polarity before connecting anything.

i Was using an isolated converter so I would have to connect the positive. What I don’t understand is why would a ttl output with signal voltages of 3 volts have a Vcc voltage of 25volts. I think my bms must be faulty. Comments under the video on Andy’s channel suggested I should have been able to just use the usb to ttl converter. Not the JK ttl to RS485 converter then a RS485 to USB.
I would like it if someone could measure their gps port vcc voltage, so I can tell if my BMS is faulty.

 

[meetyg]

That's what you didn't understand...
The isolated converter doesn't mean you can connect any voltage you want. It's limited to 5v, but works with1.8v, 3.3v 5v etc...

If you have more than 5v on the VCC you shouldn't have connected it.

 

[Smudgey]

Looks like 25v on the GPS port is correct.

 

[Smudgey]

That's what you didn't understand...
The isolated converter doesn't mean you can connect any voltage you want. It's limited to 5v, but works with1.8v, 3.3v 5v etc...

If you have more than 5v on the VCC you shouldn't have connected it.

I didn’t know it was 25v until I plugged it in. I would have thought a low level output port would have been 5v max. 25v is unusual. I think it is to make you buy the JK ttl to RS485 converter. I assume if I had used a none isolated converter I wouldn’t of had this problem because I wouldn’t have connected the vcc. I was just wanting to protect my Raspberry pi (ironically it did protect the pi, just not from a future fault condition)