A Better Battery Board
I wanted to create a more generic version of my battery board that could easily be used with either a Model A or a Model B Raspberry Pi without electrical or mechanical modification. The board would utilize the same electronic components of my V1 board but have a form factor that allowed it to be simply plugged into a stock Raspberry Pi. After hacking away at some prototyping PCB, this is what I came up with:
In the above left picture above the blue rectangle is a slide switch to turn on/off power to the boost circuit. The little white shrink wrapped package with six holes in it is a charge circuit with a big heat sink attached to it. The heat sink for the charge circuit was a work around that would allow the charge circuit to charge a battery at 500mA.
As for the board shape, I had to make cut outs that would allow clearance for the RCA Video jack, USB port and ethernet port. It would make the board more difficult to produce but made the whole package 2 to 3 mm thinner. This is what the board looks like when mounted to a model B Raspberry Pi (without battery):
Custom Etched PCBs
I recently had an opportunity to create a custom printed circuit board for an automation project I was helping a relative with. I watched a few tutorials on You Tube to help guide me through the process of using Cadsoft Eagle to generate a design including this one posted by Jeremy Blum. I had the boards for the automation project manufactured by Advanced Circuits and was able to get three PCBs made for $99 in about a week.
While shopping for someone to have my printed circuit boards made I ran across Seeed Studio and Itead Studio who both offer very reasonable board manufacturing costs if you are willing to wait about a month for the final product. I decided to take the plunge and try Seeed Studio with a battery board design. I went to work in eagle and had a design in a couple of days. After $30 and about four weeks of waiting I received five boards in the mail. Below is a picture of one of the boards populated and one without components installed:
If you look at the populated board on the right you can see the rubber foot that I use to support the battery board on top of the Raspberry Pi HDMI port. On the right side of the board, below the mini USB plug are two LEDs – one that illuminates when a load is being powered and the other that lights up during active battery charging. There’s enough area on the top side of the board to mount a battery ~75mm x 55mm x5mm if header pin access is not used (the batteries I can find in this size range are about 3000mAh. If the header pin pass through is used the available area for the battery shrinks to a width of just under 50mm – the batteries I can find in this size are about 2000 mAh.
Here’s a video of the battery board in use with the Adafruit PiTFT board: