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Old 06-18-2008, 06:52 AM   #1
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Smile RC18B Small Question


I may be a newbie, but I'm really puzzled with this.

I recently noticed my stock Team Associated RC18B RTR comes with a weird electronics setup. Namely, there is no 'battery input' wire going from the ESC to the receiver. There are only two servo wires connected to the receiver - one from the ESC (to regulate speed) and the other is from the steering servo.

Yet the receiver powers on without a 6v battery wire connected to it (it has a slot for it, but it's not used!).

What's the magic behind this? What would I need to do if I were to replace the receiver? The ESC?

I was under the impression you always need to connect a 6v~ BEC-regulated power wire to the receiver to power it...

Thanks in advance.
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Old 06-18-2008, 07:06 AM   #2
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The power for the receiver is coming through the lead from your speed control. Most modern electrics work this way unlike nitro's which require a seperate receiver pack.
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Old 06-18-2008, 08:26 AM   #3
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I see. Thanks.

Does that mean the ESC is the sole decider of how to power your receiver? I mean, if it can power it via the control wire (not sure of a better name for it), and doesn't have a separate power wire, then you only need the one connection.

But if your ESC is older style and has a separate power connector, then you need to plug that in the receiver.

What I'm trying to find out is do you need the receiver to *support* being powered through the control wire, or can you do this with *any* receiver?
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Old 06-18-2008, 10:18 AM   #4
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most any mini esc for cars work the same way as the factory one. no extra battery needed
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Old 06-18-2008, 04:37 PM   #5
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Yeah, the ESC typically powers the receiver, and will work with any receiver that I know of. Look at the esc (and servo) wire, itís actually 3 small wires. Positive and negative for power, and one for the control signal. The portion of the ESC that provides the power (including for the servo) is called a Battery Eliminator Circuit, or BEC. Pretty standard stuff for at least the 20 years Iíve been screwing around with these toys. Look at the ESC literature, it will generally list the voltage and maximum current capability of the BEC function.

On some old ESCs and Rx the wiring order and plugs might be different, but I believe everybody has standardized on a Futaba J setup (or close enough to it) for many years now.

Like Dad says, you generally need a receiver battery only for nitros. But there are a couple other exceptions: Modified 12th scale cars on 4 cells sometimes use a Rx pack, as voltage drop under load sometimes doesnít provide enough juice to keep the Rx and servo going well. And if you go to a high voltage setup (requires an appropriate ESC) you might need one. Again check the ESC literature, some are rated to a certain battery voltage with the BEC, but can go higher if you donít use it. Then you either use a Rx battery, or nowdays many make an external BEC that you can use to avoid the extra battery. If you do any of these, be sure to pull the red wire from the ESC out of the Rx plug and shrink wrap or tape it up safe. Other wise the 2 power sources will engage in a tug of war until one loses!
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