I received my iMax B8 battery charger today. This little device charges battery packs of PB, NiCd, NiMh, LiFe, LiIo and LiPo up to 36V with up to 7A charge current. It also has a very nice blue LCD status display and thanks to a nice eBay seller in China, I only paid 80€ for it.
The charger expects an input voltage of 11V-18V. If you only have AC outlet sockets in your house and don’t run your own solar power plant, you need a way to generate 8A of DC power in this range. Commercial voltage switching power supplies exist, but expect to pay at least 50€ for one providing this magnitude of current.
But: Nearly everybody has stacks of old PC power supplies lying around, and any nearly current one will generate 8A without any problem at all. So you can just hook the charger or whatever power-hungry device you have between one of the yellow and one of the black cables coming from the power supply and – presto – it will work. It doesn’t?
One problem is that ATX supplies don’t power up without being told so. But that’s really easy, just connect the green cable from the cable tree to any of the black ones. If you make a permanent connection, the supply will provide power whenever it get its AC current. Or, using a two-way switch, you can connect green to either black or purple for turning it on or off.
If you need some power other than 12V, your power supply might also be able to help, there’s 5V on the red cables and 3.3V on the orange ones. Also, relative to GND, you can get -5V and -12V on white and blue, although you shouldn’t count on the exactness (10% tolerance) or hight current capability of the latter two.
Just a few ideas, I’m thinking of building a nice panel with banana sockets for easy connection to all the different voltages and a nice switch and status light, and I promise to put pictures in here as soon as I’m finished.
…which is now. This is my 300W ATX power block (5€, flea market) with 4 banana sockets, GND, 3.3V, 5V, 12V. Next to it is a “real” laboratory power supply, about twice the volume and three times the wight. Both give 12V with about the same current (14A vs. 15A), but the smaller, hacked device also has the two other voltages. It has a fan (relatively quiet) though, while the commercial supply is passively cooled. Also on the picture is the charger which shows that the 12V break in a bit under load, but not problematically so.
