I got an 8S 8P battery back and a BMS connected to it. The BMS is supposed to be compatible with 6S, 7S, 8S, 9S, 10S batteries and I was told by the manufacturer to short 2 pins together to get it to work with 8S batteries as shown in the following pictures.
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I checked all the connections multiple times and also checked the voltages between each series cells and everything is correct but I could not get the BMS to start working as it wasn't giving the correct voltage of the battery. When measuring the voltage across the positive of the battery and the C- of the BMS I get around 5-6V which is not correct while when on measuring across the positive and the negative of the battery get its normal voltage 31V. Each cell has a nominal voltage of 3.7 and a max of 4.2 so the battery pack max is 33.6V. I tried to charge the BMS as shown in the following pictures to get it to work as I was told I was supposed to charge it. The battery and the BMS were charging, and the voltage of the battery increased as well as the cells were balanced (all of them were 3.9V and increased to 4.1) but I still couldn't get the correct voltage from the BMS as shown in the last picture. Also the BMS comes with a Bluetooth module to connect it to a mobile app but the module also isn't working, when connecting it to the BMS the Bluetooth module lights up for a second then turns off, also the Vcc and ground of the UART port connected to the Bluetooth module measures 10V which is weird for UART. Is the BMS defective/malfunctioned or is there something else I am supposed to do.

 

Forgot to add the links for the components used:
BMS: 6S 7S 8S 10S 25.2v 24V 29.4V 29.2V 42V Li ion or Lifepo4 Battery Smart BMS with 20A 30A 40A 60A constant current for android or IOS APP – LLT POWER ELECTRONIC (lithiumbatterypcb.com)
Charger: DC-DC Step Down Converter - DP50V5A Programmable Power Supply Buck Voltage Converter With Color LCD Voltmeter - RAM Electronics (ram-e-shop.com)
Power Supply: SMPS Input 220Vac / Output +48Vdc/7.2A (With Fan) (Industrial Grade) - RAM Electronics (ram-e-shop.com)
Li-ion cells: IMR 18650 AWT Rechargeable Li-ion Battery (3.7V , 3000mAh) – Free Electronics (free-electronic.com)

 

I suspect the BMS is not happy with the cell voltages measured for some reason and has switched off the bank of mosfets between the battery pack negative and the C- Terminal. The 6.3v is probably leakage voltage.
Are you sure that the you were given the correct info for configuring the unit for 8S operation?
Did you get this information in the form of a diagram that we could have a look at?

 

I suspect the BMS is not happy with the cell voltages measured for some reason and has switched off the bank of mosfets between the battery pack negative and the C- Terminal. The 6.3v is probably leakage voltage.
Are you sure that the you were given the correct info for configuring the unit for 8S operation?
Did you get this information in the form of a diagram that we could have a look at?

The first picture in the thread is the diagram for the BMS to configure it for 8S operation it was provided to me by the BMS manufacturer. It says that I am supposed to short pins 3 with 4 and pins 8 with 9. I saw a YouTube video where someone was using a 24S BMS for a 20S battery and he just connected the first 20 balancing wires and left the last 4 not connected but it was a different BMS company should I give it a try and just connect the first 8 wires without shorting these pins?

 

Just noticed that your BMS has an on/off function with a two wire connection, what does this do, there is little information on the manufacturers website.

 

The instructions from the manufacturer seem strange but without having any details about the circuitry or the firmware it’s difficult to comment.
If the unit is expecting to balance 10 cells then unless there is a way of changing the configuration via software or hardware ( as per their instructions) then the unit will flag an error and shut down.
Does the app allow you to change the configuration?
Some BMS systems will automatically detect the number of cell connected in series and configure the balance sensing to suit so an open circuit balance circuit would be ignored.
You could try removing the shorts and using BC0 - BC8, shouldn’t do any harm.

 

It does sound like the BMS is faulty, incorrectly configured or wired wrong... the general construct for a BMS looks like the pic below internally. If you're not measuring full battery volts at B+ to C- then the unit is either off or in over-discharge mode and therefore reading one or more cells under-voltage. Many battery management chips that handle different cell counts require certain cell pads to be shorted - the connections are rarely 1:1 - and the software configuration must know which 'cells' are actually expected to read zero else an error will occur. It's unlikely to charge or balance in that situation [edit] it may charge & balance if the balancer is purely passive as this one is and independent of the discharge control.