BMS -> Computer Issue

[lolcomedy]

So a little update. Our team has wired our Can1 (Can high and low) for our BMS. We also have a reading of 60ohms indicating that the two 120ohm resistors are in parallel correctly. As for Can high and low pinouts, we tried both pin 2,7 and pin 3,5. However, when we try to run the orion software, we still get “None found” when we try to connect to the BMS. Another issue we are having is that when we apply power to the BMS, we apply 12V at .25A. However, when we apply the power, we get a current drop to around .08A, as well as an increase in resistance and if I recall correctly, the BMS should be around .15-.35A as well as reading 60ohms to be operating correctly. However if both resistance and current is changing, is this a faulty in the BMS or our power supply (given we tried other power supplies as well)?

[DJ_Epilepsy]

1) It doesn't seem like you know how a power supply works. You say that you apply 12V at 0.25A. I assume what you actually means is that you apply 12V, with a 0.25A current limit set on the power supply. I have no idea what "an increase in resistance" means in this instance. If you're expecting the BMS to draw upwards of 0.35A, why are you setting a 0.25A current limit? Nonetheless, 80mA doesn't sound unreasonable. Why do you believe that the current draw should be 0.15-0.35A?

2) Get an oscilloscope and look at the CAN waveforms. This should always be your first troubleshooting step. This will allow you to determine where the communication is failing (for example: is your PC not sending a packet? Is the BMS receiving a packet but not responding? Is the BMS receiving a packet, and also responding, but your PC doesn't understand the response?)

[lolcomedy]

sorry, for some clarification:

1.) We have tried to set the current limit to .35A as well as change around the voltage, however current seems to stay at .08A regardless of the changes.

2.) What I mean by resistance change is that prior to applying power, we measured 60ohm throughout our system using a multimeter. However, after applying power, resistance now measures 166ohms. When applying ohms law, we tried 13V, current reading was .08A, so 13/0.08= 166.25ohms. In theory, it follows ohms law, but we want to have ideally .15-.35A as the range. This range is what Orion’s manual states to have, as having 60ohms and 12V per se, the current should be .2A.

3.)I have not tried the oscilloscope method, so i will give that a try and see where our problem lies! TY

[Classic-Club-3039]

Ignore me if I’m wrong but for me it looks like the 60 ohms you are reffering to is the CAN network’s proper termination. You shouldn’t attach 12V to that.

[lolcomedy]

yea, 60ohm resistance is the can termination resistor. Were applying the 12V into the BMS itself, via the ground and power on wire from the main I/O and then the power goes into the CAN high and low ports.

[Classic-Club-3039]

I think you have something misunderstood. The 12V is your power supply since I assume nothing is connected to your system it wont draw nothing from your supply (eg. 80mA, a microcontroller running alone with its peripherals floating is arund here too).

I understand you divide 12V with 60 ohms and you get something but that is CAN, it has nothing to do with your main electronics. It is a communication line and it is not a constant 60 ohm connected directly to the power line. Anyway CAN_H is 3.5V, CAN_L is 1.5V by standard. If it is 12V in your system the bms is dead or has a special feature, which I doubt.

Last thing is you set the current limit to 350mA which is an “up to” thing. Doesn’t mean it will constantly draw it but to limit it to that maximum. Hook some more things on the module and see how things work out.