Problems with brushless truggy

I am having a problem with something on my brushless system, I have a bk warrior 9918 and a bk warrior 9920 and a nemesis blue 7XL motor, the problem that I am having is that it cuts out after about 2 laps.
I have replaced everything except the motor. I replaced things like wires, radios, recievers, and speed controllers. If it is the motor could it be fixed?
I am running 6 cell nimh packs in a series.
I am thinking that maybe I need a bec?

on 12 cells, yes, you should use a ubec or reciever pack. i wouldnt recomend using the internal bec on anything more than 7 cells. Castles external BEC seems to be a new favorite.

[jhautz]

Yes!!! A BEC will help ALOT.

Also, what gearing are you running. If the BEC doesnt keep you going, you might need to drop a your gearing a bit to help keep the controller temps down. The 7xl is a hot motor and even on 12 cell NiMH will draw some power and heat things up pretty good. If you are looking for a racing motor with longer run times before heating up I would go with something a little lower on the kv. Maybe a 8 or 9XL would be a better chioce.

[MetalMan]

Sounds to me like the internal BEC is overheating, which will cause it to shut down, which shuts down the whole truck. Servos used in truggies can pull some pretty large amounts of current due to larger tires, so that stresses the BEC. Like A4DTM, I too would recommend the CCBEC.

[jhautz]

Agreed. The CC BEC is verk nice small and powerful. Only downside to the CC Bec is that if you dont already own a CastleLink wire, you cant change the voltage from 5V to 6V. If you have a casle link from one of the Mamba25 ESCs then you are fine. Otherwise you have to buy the CastleLink too.

[BrianG]

A little off-topic, but has anyone dissected one of those caste link cables? I imagine it plugs into the throttle cable and then into USB (or serial port). I'd be curious to know what interface IC is used...

I am running 9/46 gearing.
Thanks for the help guys!

What is the difference between a bec and just running a reciever pack?
I am kind of new to this.

[Matthew_Armeni]

Well, BEC stands for Battery Eliminator Circuit, so, it eliminates the receiver battery and you run off the main pack. Most ESC's have this built in but they cannot handle the high voltages most people are running here so they switch to an outside source. Upside to running a BEC as opposed to a Rx Battery is weight savings and one less thing to charge.

How many amps does the bec have to be?

[Matthew_Armeni]

Well that's up to you, I think they are all at least 3 amps (I'm not sure), but if you have really powerful servo's you may want more, but one with 3 amps that can run your cell count should suffice.

Originally Posted by jhautz

Agreed. The CC BEC is verk nice small and powerful. Only downside to the CC Bec is that if you dont already own a CastleLink wire, you cant change the voltage from 5V to 6V. If you have a casle link from one of the Mamba25 ESCs then you are fine. Otherwise you have to buy the CastleLink too.

Yeah, I will probably get the CC BEC like you said, will I need to go to 6V or would I be OK at 5V?

[Matthew_Armeni]

Well I'm running 5v right now, didn't know thats how the CC BEC came stock, that's kinda dumb if you ask me, but I'm sure there's a reason for it. Anyway, it seems to be enough for my Revo, traxxas 2055 (80 oz) brake servo and a hitec 645 (133 oz) steering servo, no problems.

yeah, I run a 645 too.
Thank you guys SOOOO much for the help I really appreciate it!

[jhautz]

Originally Posted by crazy4wdracer

Yeah, I will probably get the CC BEC like you said, will I need to go to 6V or would I be OK at 5V?

5V would be OK. You will just be missing some of the oomph the servo might have. I prefer running 6v just to get all of the power I can out of the servos. In a truggy you pretty much want as much as you can get.

In reality all you need to do is find someone that has the CastleLink and you can change it to 6v and you will probably never need to touch it again.