Over the past several years, I've used many different cell holders for testing batteries. I've tried many options from the cheap leaf spring cell holders to expensive aluminum-framed universal cell holders, but none of them got everything right. So I designed my own to try and get as many things right as possible.

This is aimed at product designers looking to verify cells from a manufacturer, people hoping to expand battery lab testing channels while keeping costs low, or for people like me that just like getting their own accurate data without breaking the bank on proprietary cell holders from large organizations.

The cell holders are NOT ASSEMBLED. You must do the assembly yourself. See the Assembly section below.

Features

• 4-wire contact for accurate voltage and internal resistance measurements
• Fixed position frame - don't need to adjust every time you put a new cell size in
• Installation guides to center the cell before it is clamped in at the terminals
• Airflow channels through cell holder base for easier cooling without affecting adjacent cells
• Single connector connection to test equipment - easily swap between equipment and cell holder configurations
• Push Release for spring-loaded cell contacts - don't need to push on the cell when installing (optional)

Versions

5A 3D-Printed with PETG filament
Best for low-current, ambient temperature testing only. Ensure cells will not heat above 45C under applied loads
Max temperature 45C
15A made from fiberglass (PCB material)
Includes larger cell contacts, thicker 16AWG wires for current path and equivalent traces through PCBs
Max temperature 90C
With Push Release
Includes a tab at the end that you push to release the spring loaded cell contacts for easier cell installation and removal
The push release tab is 3D printed, but the cell holder is made from the material selected.

If you choose to print the parts yourself, you can find all the required files at the links below.

Connectors

To connect to this cell holder, a connector with screw terminals is included. Supported wire gauge of the included connector is 12-24AWG.
When using screw terminals, please install wire ferrules on stranded wires to prevent accidental short circuits and loosening over time.
Connectors have 5.08mm pitch.
Additional connectors that fit the connector on the cell holder are available here.

Compatible models also available from other connector manufacturers. These seem to fit based on the images and specs, but have not been verified. There may be issues with increased pull-out force, not clipping in correctly, etc.

• TE Connectivity 796634-4
• Amphenol TJ0451530000G
• Molex 0395300004
• Phoenix Contact 1757035

Dimensions

18650 3D Printed Version
Base: 147.5x40mm (push release adds 27mm when fully pushed down, total length required 174.5mm)
Height: 35mm (40mm with push release)
Mounting holes (M3): 135.5x31mm, 5mm depth
21700 3D Printed Version (5mm longer than 18650 version)
Base: 152.5x40mm (push release adds 27mm when fully pushed down, total length required 179.5mm)
Height: 35mm (40mm with push release)
Mounting holes (M3): 140.5x31mm, 5mm depth
18650 15A PCB Version (2.5mm longer than 3D printed version)
Base: 150x40mm (push release adds 27mm when fully pushed down, total length required 177mm)
Height: 35mm (40mm with push release)
Mounting holes (M3): 138x31mm, 5mm depth
21700 15A PCB Version (2.5mm longer than 3D printed version)
Base: 152.5x40mm (push release adds 27mm when fully pushed down, total length required 182mm)
Height: 35mm (40mm with push release)
Mounting holes (M3): 143x31mm, 5mm depth

Assembly

Assembly instructions will be available soon. The process is relatively straightforward, and takes around 15 minutes to complete. If you have experience with assembling electronic kits, you should be able to assemble it just from the pictures.
Assembly instructions for the 3D Printed version are available here, and the PCB version here.
You should be comfortable soldering, crimping screw terminals, stripping wires, using epoxy (and have some on hand), and have some standard size wrenches/sockets.

Includes:
Wires, cut to length but not stripped
Terminal block and screw terminal connector
4-terminal spring-loaded contacts
Wire crimp terminals for power contacts and push release handles
Nuts, bolts, standoffs, washer, for connecting wires and mount locations (including to embed in the 3D printed base)

Does not include:
Solder (to attach sense wires to 4-terminal contacts, and all wires to terminal block)
Epoxy (to fit the 2 sides of the push release tab, and hold the terminal block in the 3D printed version)
M3 bolts to mount the cell holder to a surface

3D Printing Files

If you chose to print the parts yourself, you can download the files, as well as find instructions for printing them on Printables here.

Source code link is a link to a python program I made to test batteries using standard lab equipment, where I use this cell holder all the time!