Background
The High Voltage and Energy Storage Group (HVES) is a research group within the School of Engineering, Computing, and Mathematics at Oxford Brookes University. The group focuses is developing novel solutions to problems within the energy storage and future of transport fields. This includes multi-scale numerical modelling, electrochemical testing of lithium-ion batteries, and optimal control research for battery management and high-voltage powertrain systems. The group also has experience in optimal high power battery pack design and second-life applications of packs. Additional information can be found at https://hves.brookes.ac.uk. As part of the electrochemical testing, a fixture was designed to apply pressure to the outside faces of a lithium-ion pouch cell to provide a more accurate use case when completing cell level testing.
Fixture Overview
The fixture is a modular design that can accommodate cells that are 36mm to 50mm wide and 125mm to 145mm long. Pressure is applied to the cell through a double top plate that has Flexiforce sensors in between to map out the pressure distribution. A total of 14 M5 hex head screws are available to create the desired distribution based on the pressure and cell geometry being used. Nylon dowels are used to position the cell in place.
Two busbars are clamped onto the battery tabs with M6 bronze fasteners for current load and there is a gold-plated copper piece for voltage sensing. Current development is looking at creating additional lower bus bar designs to account for higher current loads with M8 fasteners.There is a grid system for thermocouples to be placed at various locations across the cell surface.
Exploded View & Bill of Materials
An exploded view of the assembly can be found in the image below with a bill of materials available in the table below.
| Part Number | Part Name | Quantity |
|---|---|---|
| HVES-FIX-PRES-01 | Pouch Pressure Fixture - Top | 2 |
| HVES-FIX-PRES-02 | Pouch Pressure Fixture - Bottom | 1 |
| HVES-FIX-PRES-03 | Copper Clamp - Bottom | 2 |
| HVES-FIX-PRES-04 | Copper Clamp - Top | 2 |
| HVES-FIX-PRES-05 | Clamp Holder | 1 |
| HVES-FIX-PRES-07 | Voltage Sensing Plate | 2 |
| HVES-FIX-PRES-08 | Tab Separator | 1 |
| N/A | M2.5X0.45 Grub Screw - 6mm Long | 8 |
| N/A | M3X0.5 Button Head Cap Screw - 6mm Long | 2 |
| N/A | M3X0.5 Button Head Cap Screw - 10mm Long | 8 |
| N/A | M4X0.7 Button Head Cap Screw - 10mm Long | 4 |
| N/A | M4X0.7 Hex Head Bolt - 60mm Long | 4-14 |
| N/A | M4X0.7 Hex Nut | 4 |
| N/A | M5X0.8 Button Head Cap Screw - 25mm Long | 1 |
| N/A | M5X0.8 Hex Nut | 1 |
| N/A | M6X1.0 Brass Hex Head Bolt - 25mm Long | 2 |
| N/A | M6 Brass Spring Washer | 2 |
| N/A | M6X1.0 Brass Hex Nut | 2 |
| N/A | 3mm X 6mm Long Nylon Dowel | 7 |