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I decided to make a confluence page as I validated the BMS carrier rev 1.1, so here it is. I’ll be following the validation guide (Validation - BMS Carrier ).

Before Starting

  1. Inspected the board thoroughly for solder bridges and bad solder joints, and fixed up a few.

  2. Gave the board a good clean with a toothbrush, ethanol (rubbing alcohol) since I didn’t have any isopropyl alcohol, water, and a cloth.

  3. Made sure the controller board that I was going to use works by running the booard validation scripts (Board Validation ).

  4. LEDs were checked for the correct polarity.

    1. LED5 (which is actually a duplicate of LED4), the fan indication LED was installed backwards.

At this point, the isoSPI ICs are not populated, nor are the micro fit connectors for the HV relays, killswitch, or fans. We will add them as necessary as we go through the test. This board has already been powered up and some testing done - 12V was initially connected backwards, so there could be more issues on this board.

Power Validation

  1. GND, 3V3, 5V, and 12V test points are all isolated from each other, tested with the multimeter continuity test.

  2. Removed R23. This is a 0 ohm resistor between the Current Sense output of the load switch and the input of the MCU for measurement. Why do we need to remove this (Liam Hawkins)?

  3. Without the controller board connected, 12V tested good. Installing the controller board, both 3V3 and 12V are good!

  4. 5V does not seem to be powering on. It slowly rises to 1.8V, and then stays there. I was artificially turning on EN with another power supply connected to wires I had soldered to R3. I realized that the wire also touched R2, and caused this behaviour. Fixing this, the 5V converter works and we get 4.935V.

  5. 86mV Vpp on no load, 20mV Vpp for both 1A and 2A loads. Oscilloscope was set to AC coupled, triggering on rising edge, with a 1X probe connected to the GND with the probe’s alligator clip.

    1. Note - Good page on measuring power supply noise: https://www.edn.com/testing-a-power-supply-noise-part-2/

^ No load

^ 1A Load

^ 2A Load

Power Validation Part 2

I replaced the LTC6820 ICs and am now getting a 0.22V on the 3V3 rail. They seem to be drawing too much current or causing a short. When not powered, the 3V3 line does not show any signs of a short, has about 170k of resistance to GND, whether or not the controller board is in place - this test was done measuring between the 3V3 and GND connections on P7, which it turns out is not correct. The GND that is labelled on this connector on the rear (which I assumed was the board GND) goes through the HV relay activation FET before going to board GND. So I was never measuring the real GND point when measuring this resistance. A careful look through the schematics would have revealed that, but fixing the silkscreen to not show GND might also be a good idea. Measuring between the GND test point on the right side of the board and 3V3 indicates about 1Ohm of resistance → so we found an issue - likely from the isoSPI ICs.

I double checked the pin assignment and layout for the LTC6820 ICs and it all seems good.

So my conclusion is busted ICs, likely due to the original plugging the board in backwards. We will order some extras and test it out.

Now I need another working controller board to complete the validation.

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