Ianhill said:
China does a 120vdc to 12vdc 20 amp max dc-dc step down convertor, 3 wire shared common and phases.
At 90v or 24s some 110/240vac to 12vdc 2amp etc mains transformer plugs will work im not sure on how the circuit manages to oscillate the primary to secondary but its handy none the less for powering a few leds etc.
I've been using purpose build DC-DC converters for a while, but a switching power supply that will take a variable input voltage will work just as well. This is the DC-DC converter I used in the Currie.
http://www.ebay.com/itm/24v-48v-72v-96v-108v-to-12v-20a-dc-converter-adapter-for-electric-car-battery/332022644641?hash=item4d4e177fa1
or for a bit more voltage and physically larger, I have one of these too, but the voltage range isn't high enough for my moped. I need 130 volts at least.
http://www.ebay.com/itm/electric-36v-48v-60v-72v-120v-converter-12v-20a-transformer/142042804440?hash=item21126930d8
I also knew that AC switching power supplies will also run on DC. I looked around until I found a 12 volt, 10 amp power supply that had a decent input voltage range and bought one on ebay.
http://www.ebay.com/itm/191981131504?_trksid=p2057872.m2749.l2649&var=491530307177&ssPageName=STRK%3AMEBIDX%3AIT
I've had this power supply 2 days now. I plugged it in long enough to see it worked and then took the case apart and started modifying the power supply. There were two tabs on the circuit board on either end that I cut off. They were only extending the AC and 12 volt lines out a little. I soldered wires directly to the solder traces and saved about 5/8" length. The red/black wires on the right end are the AC input side and the left yellow/brown is 12 volts out. To be sure no pins on the bottom side of the board ever wore through the insulation, I laid down 4 layers of electrical tape before running the input wires across the PCB. The power supply was rated for 100-240 volts AC. I've tested it as low as 69 volts DC (18S) and it still outputs 12 volts. I tried 48 volts (12S) and that didn't work. At $15, that's much cheaper than a true DC-DC converter. On the input side there is no right or wrong way to connect DC to it. It was designed to run on AC after all. This power supply will go in my Moped build. It is physically the same size as the second DC-DC converter I listed, but at much less $$ and much more input voltage range. I'll wrap the whole thing in 2" kapton tape to make it water tight. The output is 100% isolated from the input...perfect for EV uses.