Hardware Hacking Projects for Geeks

21

Chapter 1, How to Build a Portable Laptop Power Supply

Drill a small pair of holes in one edge of one of the battery packs. Take a tie

wrap, thread it through these holes, and use it to capture the power cable.

In the battery pack in Figure 1-8, you can see where I secured the cable on

the left side.

After soldering the wire tabs between the pack and the power cable, you will

want to cover over any exposed metal. If you have access to heat-shrink tub-

ing and a heat gun, I suggest you use this material to cover over the exposed

metal. If you do not have heat-shrink tubing, use black electrical tape.

6. Test out the pack

Install the D cells into the battery holders. Set a multi-

meter to measure DC voltage and touch the probes to the

end of the connector. The meter should read a voltage

slightly higher than the number of cells multiplied by 1.5

(newly purchased cells often show a higher voltage than

1.5 volts). If you cannot read this voltage, check your wir-

ing and the installation of the cells.

And your laptop battery extender pack is now complete.

You should get anywhere from two to six hours of extra

run time for those long plane trips.

Project Demo

Plug your laptop into the battery pack. The laptop will show that it is

plugged into a wall outlet while using the battery pack. This is because the

pack is supplying power through the power jack normally