I've done this before. All the instructions are pretty much the same. You can get all the parts for about $10 at Radio Shack. Works really well. Just make sure you have a large enough power supply to give you the Amps you need. I used a 450, which is plenty for my chargers. Also, make sure you have a multi-meter ready, you need to make sure you are getting as close to 12V as you can out of it, if not, you will not be able to charge 12V packs like your transmitter batteries unless you combine the 12 and 3V leads. But then you have to make sure your charger is able to take the 15 to 16 volts you are going to get from doing that, other wise POOF.