Sunday, May 15, 2011

eBay Hack Charger #7,523

I really should start a project page for random power supplies that I put together with junk from eBay...

A few weeks ago, I re-purposed an Xbox 360 power supply for my battery charger, and commented on how nice it would be to have a flat OEM power supply brick like this one from TDK Lambda instead. Well, I didn't find that on eBay, but I may have found the next best thing. Vicor is another manufacturer of shiny OEM power converter bricks, and I happened to come across a lot of these:

Turns out Azure Dynamics, a local EV technology company, has an eBay store, presumably for stuff they don't need anymore. I'll be sure to check back regularly. The VI-251-09 brick takes 100-300Vdc and puts out 12V at 200W. I also managed to find a matching Vicor input rectifier module, though presumably any bridge rectifier could work. Combined, the rectifier and DC/DC converter are functionally equivalent to the XBox 360 power supply, but a lot smaller. Some assembly is required, though:

The input is 120Vac and the output is trimmed up to 13.2Vdc. In between, I added a two-pack of 200V, 330μF capacitors. This buffers the rectified AC at the input to the DC/DC converter. The disk-looking capacitors between the terminals and the baseplate are recommended in the datasheet for EMI protection, i.e. they are probably not necessary.

And as usual, I found a random heat sink in MITERS that was already the perfect size for fitting the input rectifier and DC/DC converter brick. I added the fans after experimentally determining that they were needed to hit the full 200W output. Through some sort of luck, the 8-32's I happened to have lying around self-tap into the heat sink fins. Since I'm not an HVfrosh, I thought it wise to insulate all the high voltage pins and ground the heat sink in the final configuration.

I also randomly found a box/carrying case that everything fits in perfectly. There's even a little square left for the balancing lead breakout board. I really should stop measuring things and just look around until I find things that are exactly the right size. It works well.

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