My main design goal was a handheld battery powered induction coil. This design is for short duty cycle use ( 10 - 15 seconds) such as loosening rusted nuts, heat treating small tool bits, brazing, soldering, or my favorite, heating a titanium nail. I used a popular ZVS circuit from this forum: http://4hv.org/e107_plugins/forum/forum_viewtopic.php?122354 Thanks Marko!
This fits on a 2" diameter circular board glued to a 1" thick aluminum disc heatsink with Arctic Cooling's thermal epoxy. Anodizing the heatsink is highly recommended as the oxide layer is nonconductive. Otherwise it's difficult to epoxy the pcb to the heatsink without any shorts.
The driver connects to a tank circuit made up of 8 - 1uf CD capacitors and a 4 turn 1/2" diameter work coil via (2) 1/4" brass busbars. This tank runs at about 137KHz and works very well for my work piece size. Coil size will be limited by frequency, larger coil equals lower resonance frequency which cause the input inductors to saturate easier (over heat). You can offset this with lower capacitance again within limits. Larger work pieces with larger power requirements will need larger inductors.
I used (4) A123 LiFePo batteries for power as they have a very high discharge current rating and are currently the safest lithium battery tech available. I don't recommend other lithium batteries as I feel they don't have comparable high current drain capabilities and are still too unstable... Youtube is full of video examples.
I bored out (paper thin in some areas, lol) a Sky Ray King flashlight and managed to cram everything in using 4 18650 size batteries. This will heat a Highly Educated Flux Titanium style nail to cherry red in about 10 seconds. Using the larger 26650 cells the heat time reduces to less than half at the expense of extra bulk.
The Kicad files with "mc" in the name are for a single sided metal core pcb which I have not tested yet.
I have used https://www.itead.cc/open-pcb.html and http://dangerousprototypes.com/store/pcbs, the latter is Dirt Cheap Pcbs. I like Dirt Cheap as they offer 0.6mm (thinner = better heatsinking of FETs) at no extra charge and 2 oz. copper for $20 extra.
Images also hosted on https://hardboiledfrog00.imgur.com/
*Plus many more induction and zvs related threads on http://4hv.org
*I recommend 2 oz copper for the pcb.
Safety Notice and Disclaimer
All typical precautions regarding induction heaters and lithium batteries apply! Keep away from medical devices, metallic implants, rings, jewelry, and electronic equipment when operating.
*I highly recommend a fuse installed on the battery pack: http://www.ebay.com/itm/111817931948
Not responsible for any Darwin Award winning self-induced injuries. If you don't have the necessary skills then pay someone who has to build it for you and teach you how to operate it safely. Support your local geeks. :)