Problem with Stock motor.

GST 7.7 , Nemesis 7.7 , GSR 5.0

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Problem with Stock motor.

Postby pfitchie on Tue Oct 28, 2014 10:11 pm


This posting is more so directed to support. I purchased my CEN GST-E Colossus back in early June. Now in early September I was out driving the truck and had performed several small jumps. The truck was what I would now call "browning out" which it had done almost since day one but was much worse. Basically if you punched the throttle the truck would launch, stutter, then about 1 sec later launch again, if I eased the throttle it would not do this. Radio control was lost during these brown outs. After about 3 minutes of running the truck stopped and massive amounts of smoke began to pore out. I was able to remove the body and remove the batteries which ballooned to almost 3 times their original size. All connectors from the battery side of the ESC to the batteries where desoldered.

I took the truck home and I figured this is all part of the game, maybe the esc went bad from a jump or a lipo had an internal short. Curiosity got the best of me so I took the ESC out of the truck and disassembled.


After a visual inspection it looked like maybe the fan wire had shorted out on the side of the esc pcb. I shelved the truck until I could afford to but a new ESC and LiPo's.

2 weeks ago I received my HobbyWing Quicrun 150a ESC and new 50c 6000mah LiPos. I immediately installed ESC and charged lipos. The brownouts continued during my first test run to the point that the truck was undriveable. In discussions with the Facebook Colossus group everyone told me to install a BEC. I did and the radio brownouts stopped but the truck continued to stall when punching it. After about 2 minutes of running LVC on the ESC kicked in. When I checked the lipo voltages the came out at above 4v. I visited my LHS thinking I had a lipo problem and they where kind enough to let me try some 80c trackpower lipos with no improvement.

I played with various LVC voltages and other ESC settings and did not get any significant improvements until I turned the default timing value to 0deg. I could now get about 4 minutes of uninterrupted running with the truck. However once the lipos went under 4volts the LVC started kicking in. I finally bit the bullet this past weekend and bought a new Castle 1515 motor and installed it. The truck runs awesome and I was able to remove the BEC as well. Brownouts and Stalling are completely gone.

I am now almost certain that the motor was defective from new but was very hard to suspect since it seemed to perform well. I am also certain that based on the LVC behavior with the higher amp ESC that the stock motor is the direct cause of the stock ESC and resulting cascading failure of the LiPo's due to excessive current draw. This excessive draw would cause the ESC to brownout causing the stalls.

I am wondering what support has to say about this, while I understand at this point I'm out of the warranty period but at the time of the failure I was so close to with in the 90 days. I purchased the colossus on June 2/2014 and the ESC and lipos went up on Sept 7/2014. The truck had maybe a total of 10 full packs run through by that time.

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Re: Problem with Stock motor.

Postby CEN Racing on Wed Oct 29, 2014 3:42 am

Hi Patrick

Thank you for choosing CEN Racing.

FYI, the stock motor/ESC are also manufacture by Hobbywing and you can contact Hobbywing USA directly for all support and warranty claims.

The hobbywing ESC itself has temp/voltage control and will shut off if the limits were reached. This is the "punched the throttle the truck would launch, stutter, then about 1 sec later launch again," scenario you were experiencing. The stock ESC can only handle 14.4v / 4S lipo and anything beyond that will trigger the control.... damage can still occur even with the temp/volt control. Also, some manufacture advertise their 4S lipo with 60+ C as a standard 4S, however, those super high C-rate lipos actually produces more than 14.4v of instant burst.

If the fan shortcircult, the fan itself will just stop working. The fan itself will not interference with how the truck runs. If the lipo iself ballooned up to 3 times the size, its not a quality lipo for sure.

Of course, we are just assuming as without seeing the truck and test the motor/ESc, we cant give you a definite answer. If you think the motor is defective (and since you already have a new motor), send it to HObbyWing USA and see what they can offer you.
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Re: Problem with Stock motor.

Postby Smaug on Tue Apr 28, 2015 8:09 am

FWIW, I also had to install a BEC. I have a Castle 1515 motor in mine, and a Mamba Monster ESC.

The steering servo (a Hitec coreless digital, rated at 250 oz-in) was causing brown-outs, just like the instruction sheet warned of. Those big tires and a fast, powerful servo are quite demanding, more so than can be supported by the onboard BEC of many ESCs.

I velcroed an "Ultimate BEC, 3A" to the outside of the chassis, and no more brown-outs. I consider it just part of having a monster truck with big 7.5" tires. It will either not have enough steering throw, will be slow, or will need a BEC not to brown out.
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