Portable Lab Power Supply

This is the third installment on reusing a laptop battery pack.

A good lab power supply is a necessary tool for any hacker's workshop. It would be even more useful if the power supply is totally portable so one can work on projects anywhere.

The core of the portable power supply is the variable power supply module. The module accepts input voltage from 12V to 24V and can output voltage from 0V to 30V. A perfect range for any experiment.

The output current depends on how much power the battery can provide. The power supply can output up to 5A of current, but most battery packs will cut out much sooner than that. I suggest not drawing more than 30W from a single battery pack. If you connect multiple battery packs together, you can draw more power out of it.

Other parts needed are:

• Power terminals, red for positive and black for negative
• Barrel connectors for power input from battery and power input from MPPT solar charger
• Power switch
• Screw and spacer for mounting PCB
• Wire, AWG18 or larger

Link to the power supply module: https://www.amazon.com/gp/product/B0793FCLWN

I printed the enclosure on a 3D printer.

Attach the terminal and display unit to check the fit of the printed enclosure.

The power switch and the socket doesn't need to be installed yet. It is better to install them after the power converter board is installed first.

Socket is glued onto the case using super glue.

The wiring between the pieces are fairly straight forward and self explanatory

Install the power converter board, attach wire from the power converter board to the output terminal. Solder the wire to the output terminal.

If you are using PLA printing material, you probably want to solder the wires outside of the enclosure prior to installing them so the heat from the soldering doesn't melt the PLA plastic.

Install the plug, the socket and the switch for the input power. Solder them together with AWG18 or thicker wires to ensure good current flow.

Install the ribbon cable to the display unit.

Now the system is fully wired.

Just peel and glue them on.

Attach the cover for the power supply. The cover held in place just by friction. Once the functional check is done, I glue the 4 corner down by heating the PLA material and melt them together.

I use simple Velcro strips to attach the battery pack to the power supply unit.

The power supply module has quite a bit of inrush current during power on. Some battery pack might now be able to provide sufficient current for the module to turn on. Thus, it may be necessary to add a booster capacitor. I use a simple design that has a capacitor (2200uF, 16V) attached to a barrel connector. When needed just plug the booster capacitor to the charger socket.

Just for your information, the power supply module is a combination of two voltage converter module. The first stage boost the input voltage to 35V. The second stage is a variable bulk converter that down convert 35V from the first stage to the voltage set by the user.

When the power is applied to the power supply module, it has to charge up the 35V intermediate voltage capacitor. This is the cause of the large inrush current.

Now you have power anywhere you go!

The design works as a standard bench top power supply. Simply use any power brick, anywhere from 12V to 24V will work just fine. Make sure the connector polarity is positive center, negative outside.