Lipo and cogging with brushless....

[Colinevan]

Well just to report that iv just finished trial runs of my rb5 running its new trakpower 4900 and the gtb 5.5 sintered brushless.

Iv also installed the novak safety cut off device, and have noticed that if from standstill i accelerate to the max, the motor cogs and ticks away then accelerates as norm. (This can take around 1 sec and you can hear it ticking\clunking noise and the car judders) If i accelerate smoothly from standstill it is fine and has no side affects at all.

Apart from the prob above, the car has loads of power and stayed like that for a good 8 mins or so before the rain came in. If anyone likes the idea of a fast virtually maintenance free car then this will appeal.

Has anyone else had similar probs with there brushless and lipo?

If so did you find a remedy or might there be a fault with my setup?

Thanks.

Col.

[DanW]

Control your left thumb a bit.

Depends how bad it is, a lot of brushless, even sensored systems will cog if give it instant full throttle. Even off the start line you need to control the acceleration a bit.

If it causes a problem check the sensor wire, and the position of the sensors.. sometimes they can get moved.

[LEGEND]

What have you got your throttle curve set too. If it is too high then that maybe the problem and you may need to bring it down a touch, this will smooth it out a bit. If that does not work then you may want to try a capacitor on your speedo. I think this helps smooth out the voltage going to your motor.

[DCM]

I think you will find that there are to many 'connections' between the cell and the esc, Tekin recomend the use of good quality connectors on brushless, as the slightest hindrence there can cause cogging.... you could try it without the Novak cut-off and see how it goes?

[Fiddybux]

Col,

Don't know if it makes a differnece, but is that the GTB with the blown capacitor?

Russ.

[Colinevan]

No russ, this is the new one that i bought solely for the rb5.

I emailed Novak with the problem..... Heres there response, it may help others as well.

Hello Sir,

I see this problem all the time and it comes from two basic situations. The Most Common By FAR, is that the Battery Voltage is “dipping” to lower then what the RX works with. So the RX cuts in and out in and out when you mash the gas. Very very common with spectrum radios, and entry level FM stuff. But I’ve seen it with the High End RX/TX setups as well.

The fix is to lower gearing, or add a “receiver capacitor”. We sell one with a plug on it called the “glitch buster”, Spektrum sells one they call the “Receiver Filter Capacitor”. They both do the same thing, give the RX power when the voltage dips for that brief moment.

Next is that your Smart Stop has not been ‘programmed’. It has a button and needs to have the one touch setup done as well.



I will try messing with the smart stop first, and post the results,




Col.

[DanW]

Hmmm,

Voltage dip... used to suffer that many moons ago on certain RX speedo combos

But shouldn't be a problem with decent lipos - there supposed to have a very small voltage drop under load when compared to Nimh or Nicd. The other possibilty is that the BEC circuit in the speedo isn't as good as it should be.

Although i've run GTB in the 4WD, geared high, 6v high power digital servo, fans and PT all running off the RX and no problems. So i would say the BEC from Novak is definately upto the job.

The "smart stop" is a lipo cut off device? If your GTB is new it should have integrated Lipo mode???

You could try removing the smart stop for a test as long as you remember not to run the car too long.

[Colinevan]

Well just an update really, decided to give the car a quick balst and noticed that the clunkingz juddering seemed to be worse still.

Eventually the car was only going half throttle and if i upped the power a bit, it would just stagger along.

No magic blue smoke, but the motor doesnt want to turn at all now. If i spin the comm manually, and accelerate ( i.e bump start ) it will start but not rev very high.

I stripped the motor down to see how the rotor was ( i had suspicions on a shattered sintered magnet ) but it was fine .

Tommorrow i shall test both the speedo and motor and find out what has gone wrong with it

Col.

[Gayo]

You should at least try without the "smart stop" to see where is the problem coming from.

To me, that kind of devices (the "smart stop") is useless if you know what you're doing. Just stop running as soon as you feel that the power decreases and your Lipo will be fine. That's what I do anyway (original Sphere and LRP 5000 Lipo).