BMS Testing PCB
Overview
Section titled “Overview”We will use this PCB to simulate battery cells, that can be connected to the BMS segment boards, so we can test cell readings & communications between segments.
The Segment PCB has 2 Molex FFC (Flat Flexible Cable) connectors, these two connectors route voltage taps and thermistors to the segment.
- 39-53-2204 - 20 Pin FFC
- 39-53-2084 - 8 Pin FFC
- Cable used between segment and testing pcb: 1.25mm Pitch Premo-Flex FFC Jumper, Same Side Contacts, cable length TBD
Block Diagram
Section titled “Block Diagram”![[ev2026/electrical-systems/battery-management-system/assets/bms-testing-diagram.png]]
Connector Wiring
Section titled “Connector Wiring”- I designed the top and bottom PCBs to be interchangeable, but unfortunately, the wiring to both the connectors is different for both boards.
- The Testing PCB will have 2 8-pin connectors and 2 20-pin connectors
- For the Bottom configuration, just connect the Green and Purple Labels, ignore the Red.
- For the Top configuration, just connect the Red and Purple Labels, ignore the Green. ![[ev2026/electrical-systems/battery-management-system/assets/image-2.png]]
Testing PCB Requirements
Section titled “Testing PCB Requirements”- Make a 2 or 4 layer PCB. Small PCB isn’t that important, since its only for testing, keep it under 8”x8”
- 24 Cell simulator:
- Use a resistor divider to divide the input supply.
- 24 x 4.2V = 100.8V, We don’t have a power supply this high, but we can still test using our 30V power supply (I’m working on getting a higher voltage supply)
- 20 Thermistors
- Use NTC Thermistors: NCU15XH103F6SRC
- Add a way to connect to the 30V power supply, maybe something like the power supply cables used in labs
- Add plastic standoff screws to the PCB, we don’t want the PCB to be touching the table we put it on
- Add a enable/disable switch for each cell connection, so we can test Open-Wire, I was thinking a DIP switch like this: ![[ev2026/electrical-systems/battery-management-system/assets/image-3.png|399x399]]