I am new so this may be a stupid questions. I am looking to buy a buy controller (Radio) from ebay with a receiver and a few servos. The problem is that all the receivers don't have batteries. I know the battery depends on what you are trying to power, but I also know that a lot of receivers have special connection so you just can't buy any battery. Where can I buy a battery for a receiver, or am I just totally wrong.

hi bro.....
if you are a totally new in this hobby
don't don't burden yourself in buying it at ebay
just go to our nearest hobbyshop ( that sell RC of course )
they'll be more then willing to explain to u bout all your doubt

in my place..
reciever battery use standard futaba type connector
if u are planning to buy either
sanwa/airtronics or KoPropo brand radio gear...
u must change the connector accordingly
otherwise it will crack your reciever.

does not comply if u are planning to buy AM radio

Shouldn't be an issue, all of my radio systems have included a battery holder for the receiver. If you are buying used parts here and there, just ask about it. I know I have several laying around that I've never used except for occasional troubleshooting. If someone is selling used stuff they probably have them too. Or shops sell them for like $5.

I may be wrong, but I thought the different plugs were history, doesn't everyone use Futaba J compatible plugs on servos and esc nowdays?

And I strongly agree with cbd that a local hobby shop is a good place to go. Just because it's online doesn't automatically make it cheaper. Sometimes this stuff doesn't work, a good shop will take care of it. Shops frequently have used stuff, or know a regular customer that does. Ask around, look for bulletin boards, hang around race tracks.

Oh, hi Matthew, I didn't reconize you at first. If you pick up some older stuff, it will still probably work. The main thing to watch for is the wiring order. Some of the old KO PROPO stuff, others too I'm not familiar with, used the wires in a different order. Generally you could carefully pull the individual wires out of the connector, pushing down on the partially exposed metal tab on one side, and reinsert in the correct order. Black -, red +, and other, the signal wire. Some don't have actual black, but use the darkest hue for black. You do have to have something that goes together to follow, or find somebody who knows that equipment. And you may have to trim the actual connector some to get it to fit, trimming off a rib on one side is common. Of course the rib was there to keep you from plugging in backwards, so be careful.

And remember, if your setup includes any electronic speed controls, they power the receiver, no battery needed. That's why there are a lot of them laying around. Only one power source, or something will end up blown. Including if you have 2 escs, pull the red wire from one of them. Receiver batteries are generally only used for nitro powered toys.