VoltTemp Board
Status | Initial Testing |
Owner | @Clark Rucker |
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Approver |
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Due date | -- |
GitHub | |
BOM |
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Due Dates:
Requirements/Considerations - 2/20/2025
Component Selection - 2/20/2025
Initial Schematic - 3/01/2025
Initial Layout - 3/20/2025
Rev. A Ordered - 4/20/2025 ?
Firmware/Testing - 06/01/2025
Will be tested during the summer.
Description/Purpose
Measure the voltage across battery modules.
Each battery module consists of 9 cells in parallel.
Measure the temperature of battery modules using thermistors.
Each module will have 4 thermistors, however the board can support more.
Requirements
Must be able to monitor voltage of at least 4 battery modules. Should be possible to adjust configuration based on alternative cell configurations.
Must be able to monitor temperature of at least 4 modules. Should be capable of handling more inputs in case we decide we would like to monitor additional components.
Application Note
Interfacing with the BMS chip for voltage monitoring:
On the right side of the board there are two 1x5 nano-fit molex connectors. Starting from the top of the board (near the reboot button) and heading down, connect the tap for the next module.
There are dead pins on the connector to prevent shorts. These dead pins are marked on the PCB with an X where the connector is soldered to the board.
For the default 4 module configuration, shorting VC3&VC4 is required. This is accomplished by placing a 0Ω resistor near the BMS chip.
The additional 0Ω resistors are for alternative cell configurations. Consulting the BMS chip data sheet will show which need to be shorted for various setups.
All voltage taps run through a 6-pin DIP switch for scrutineering.
Interfacing with the ADC chip for temperature monitoring:
On the left side of the board are 6 nano-fit connectors for thermistors. The two larger ones are for channels 0 to 3 on the ADC and are placed on the top and bottom of the board for easier access to taps coming from the battery.
The ADC channel is indicated by a number ranging from 0-7 next to the connector.
Analog Ground is indicated by a '-' symbol. (Maybe this should change for the next iteration to avoid confusion)
Channels 0 and 1 run through a 2-pin DIP switch for scrutineering.
Interfacing with CAN:
There are two I-CAN connectors on the top of the board.
Order of connection does not matter.
Context
Location of the board:
There will be 8 copies of the board. Each one will be located on a battery segment.
Connection List
# | Name | Type | Ideal Voltage |
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J1 |
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J2 |
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J3 |
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J4 |
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J5 |
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Main
Schematics
Circuit Components
BMS Chip: BQ7692003PW
Due to our use-case only requiring 4 channels for the BMS chip, we didn’t want to go with a chip that supported much more. This is one of few chips to support 5 channels, which meets our requirements while still giving a little bit of leeway for possible changes.
Furthermore this chip offers built in under & over voltage protection, as well as integrated cell balancing.
8-Channel ADC: ADS131M08QPBSRQ1
This is a very robust 8-channel ADC which exceeds all requirements for this board.
Because this ADC meets requirements for many other boards throughout the car, it will likely become a regularly used component in order to standardize firmware across projects.
Layout
Github link:
PCB:
3D Model
Lakshay had a nice render that i will steal later
Firmware
No firmware has been written yet.