View Full Version : Sidewinder ESC combined with Castle BEC

07-10-2008, 10:06 AM
*** Don't try this unless you are very good with electronics. ***

I'm doing some electronics work under my other persona (HeyOk Performance). I thought I would share what I am up to as others might want to try this mod.

A little background...

Running a rock crawler, we want a good, affordable electronic speed control (ESC) and we want a steering system that will crush rocks :biggthumpup:

One way to improve steering performance is to make sure all the power that your steering servo could ever want is available. The part of the ESC that delivers power to the onboard electronics - the Receiver and Servo(s) - is called a Battery Eliminator circuit (BEC). The one included on most ESCs is okay for light duty use, but in a crawler, it probably isn't able to deliver enough current if you are running a really strong servo. To overcome this limitation, an external BEC can be used.

I'm going to show you a way to use a Castle BEC with a Mamba Sidewinder. This isn't the only way it can be done, there are several other methods that it could be wired up (another way would let you run your servo on a higher voltage than the receiver) but my goal here is to show a way of setting things up to reduce the amount of extra wires cluttering up your crawler. We will end up with a combined ESC and BEC that can be plugged in as one unit.

This picture shows the ESC with the BEC glued to it. The BEC is almost the right length to fit nicely along one end of the speed control's case. Shoe Goo does a fine job of holding things together. At the top you can see the bottom of the ESC case removed.

The circuit board is slid a little out of the case. The BEC's power input wires got chopped off about an inch or so from the BEC. The little bit of extra length will help give enough room to solder comfortably and can be tucked inside the ESC case after.

A close up showing how the BEC power wires were soldered onto the ESC. Ideally the wires would be soldered directly to the circuit board, but the pads are very large and hard to heat. The circuit board also has a conformal coating to help make it resistant to corrosion, so it is a good idea to leave it alone. A small amount of insulation was removed from the ESC's power leads right near the circuit board and the BEC was soldered onto there.

Now the cool part. The ESC normally supplies power to your electronics using the red (positive) wire on the cable that gets plugged into the receiver. This picture shows the red wire lifted from the pad where it is normally soldered to the circuit board. You can make out the pad where the wire came from - it is between the brown and orange wires on the circuit board. This wire will be spliced onto the BEC's red wire which is the BEC's output. Now when the ESC is connected to your receiver, power will come from the new BEC instead of the wimpy one that came with the speed control.

Remember that one of the goals was to reduce clutter. If we didn't care about ever reprogramming the BEC's output voltage, we could do away with the receiver cable on the BEC (except for the red wire!). As a compromise, this cable will be shortened. Here we can see where a small amount of insulation has been removed on the red wire on the BEC's receiver cable. This is where the red wire that was lifted in the previous picture get's connected.

07-10-2008, 10:39 AM

The ESC's red wire soldered to the BEC's red wire.

Heat shrink installed.

This is the receiver cable from the BEC. Chopped to about two inches long.

The old connector pins soldered onto the cable.

Connector rebuilt.

End view of modified ESC

Side view of modified ESC

Now the ESC and BEC can be dealt with as a unit without the messy wiring that usually comes with having an external BEC.

07-10-2008, 09:13 PM
nice job but i dont feel enough god in elctronic to try that but it's good to know that it's possible and a good option


07-10-2008, 11:45 PM
very cool:cool:

Would this be possible with my Mamba Max and Castle BEC too? Or is it not necessary with the Mamba? (i'm not sure of the dfference between the castle & mamba...)

07-11-2008, 05:45 AM
Thanks guys!

It would be very possible to do this mod to a Mamba Max! In fact it is a little easier with at Mamba Max because it is a little larger and therefore there is a little more room to work.

07-12-2008, 09:43 AM
Does this mod enable you to program both the ESC and BEC still? (using the Link)

07-12-2008, 10:01 AM
Yes it does.

I just shortened the BEC cable and then kind of tucked its connector inside the esc's heat sink. Just connect the castle link and you are good to go. Program the ESC by connecting to it's receiver cable. I verified that this worked once I had it all together. Set up the BEC for 6 volts and the ESC for brushless and auto lipo cutoff.

Hey, does anyone know how much voltage the Spektrum DX3's receiver will accept? (I will google this later but maybe someone knows off the top of their head)

07-12-2008, 01:26 PM
your workmanship is top notch with electronics, good work.:bowdown:

I may try this myself, when I goof er up, you can bail me out.:biggthumpup:

07-12-2008, 02:01 PM
Good to see you back!

I'll help if you get stuck, but I bet you can "git 'er done" yourself though!