Do I Need A BEC?

[hoovhartid]

I recently purchased an Associated TC4. I run it on a small track using a Sidewinder 4600 (CM-36) combo. After a few turns (less than 1 lap) The ESC is cutting out and shutting off. What gives?

Should I have bought the Mamba Max instead?
Do I have a bad ESC?
Do I need a BEC or what?

I know you can't answer yet. So here's the rest of the story...

When I first got it, I was running a 75t spur (largest) and a 20t pinion. This was good for about 2 laps before it hit about 190-200 deg F (Motor and esc) So I geared it down to a 19t pinion...still no good. It would shut down after a few laps. I didn't have a smaller pinion at the time so I called it a day.

I put in an order for some more pinions and the Associated Motor Cooling Duct/Fan Kit(trying to keep it cool). When it came in, I went to an 18t pinion. I went about half a lap and the car turned hard left, slamming me into the guard rail and shut down all power OK...now I'm pissed. After replacing My front A-arm and my rear axle carrier...I powered back on.
Now get this... at this point, I put the car down and turn the wheels back and forth a few times and it happends again. The wheels turn hard left and I lose all power to the car! I don't think the sidewinder can power the Rx the fans and the servo. Am I expecting too much? I took the car home and let it sit a few hours. I then turned it on, moved the wheels back and forth for about 5-10 seconds and got the same powerdown. (wheels turn hard left and esc is nonresponsive) The Yellow light(middle) is solid and the two lights on the sides of it blink/beep every few seconds.

If I unplug the fans, Everything seems to run a BIT better. I get high temps tho. 155F ESC and 165-175Motor. Also It seems that when the ESC temps get high, my steering becomes sluggish.

At this point, I'm just wondering what my best option is.

Do I send in the ESC?
Do I Replace it with the Mamba Max?
Do I buy a BEC?

Here's the full set-up;
Associated TC4 75t spur 18t pinion
Castle Creations Sidewinder 4600 combo
Associated Motor cooling Duct/Fan kit #31037
Spektrum z590 servo
Spektrum sr3500 spm1210 3ch micro Rx
Spektrum DX3.0
Zippy-K 4300 20-30C Lipo 11.1v 3cell

Thanks for reading all of this! Sorry 4 such a long post but I wanted to give all the info before I asked 4 help.

[BrianG]

On 3 cell, you should be using a UBEC. Most people may say you should be fine, but the added A draw from the fans may be overworking the MM BEC.

However, that won't help your motor temps at all. I'd look to changing gearing to fix that.

And, the way it turns left when it loses power tells me that the Spektrum needs to be recalibrated. While you bind the tx/rx, hold the throttle and steering in the position you want it to be at during failsafe. Generally, thats throttle=neutral and steering=center.

[hoovhartid]

Thanks brian,

I have a few other questions for you...
would adding capacitors help keep heat down on the esc?

similar to what you suggested in here?;
http://www.rc-monster.com/forum/show...=add+capacitor


if so, could you recommend which ones to use...maybe something like these?
http://www.mouser.com/Search/Product...u7jrHccg%3d%3d


also, how is that different from using something like this?;
http://www.horizonhobby.com/Products...ProdID=SPM1600
?

sorry for so many questions...
thank you in advance

Jarrad

[ptt81]

Here is the one I use for MM mod

http://www.digikey.com/scripts/DkSea...name=P12410-ND

It is huge and helped a lot with the heat, still got a few of them left and plan to put one on my Novak Super Sport

[BrianG]

Originally Posted by hoovhartid

Thanks brian,

I have a few other questions for you...
would adding capacitors help keep heat down on the esc?

similar to what you suggested in here?;
http://www.rc-monster.com/forum/show...=add+capacitor

It may help. It depends on where the heat is coming from. If it's ripple current caused by the motor, then yes. If it's simply the losses from EFT switching/rdson values, then not so much. That said, it won't hurt to add a coupe/few. The worst that'll happen is it doesn't help.

Originally Posted by hoovhartid

if so, could you recommend which ones to use...maybe something like these?
http://www.mouser.com/Search/Product...u7jrHccg%3d%3d

Personally, I like to add about 50% to 100% more capacitance than is already there. Example, the MM has a total of 990uF IIRC. So, I would add between 500-1000uf of capacitance total. More is better, but you don't get as much bang for the buck, plus the physical size gets cumbersome. Also, more caps of smaller value is better, so instead of one 1000uF cap, use three 330uF, or two 470uF caps. Transient response is better and there is more surface area to shed the heat.

Then, pick a voltage at least 25% higher than the highest peak voltage you plan to use. By "peak", I mean use 4.2v/cell for lipos, 1.4v/cell for NiMH, etc.
Up to 4s (16.8v peak), use 25v caps.
Up to 6s (25.2v peak), use 35v caps.
Up to 8s (33.6v peak), use 50v caps.
Over that, 100v is the next common voltage value.

Originally Posted by hoovhartid

also, how is that different from using something like this?;
http://www.horizonhobby.com/Products...ProdID=SPM1600
?

That is not a low-ESR cap. Also, it's only rated for 10v.

Originally Posted by hoovhartid

sorry for so many questions...
thank you in advance

Jarrad

Parts Express has a decent collection of low-ESR caps to choose from.

[ptt81]

BrianG, while we are on the topic, I happend to replaced all the 3 caps on MM with the 470uf 35v ones, I thougth I would be better than using 330uf 35V as suggested in the mod1 guide, will this cause any problem at all?

[BrianG]

Not that I can see. As long as the voltage is equal or better than the originals, they were soldered correctly, and they are truly low-ESR types, it'll be fine.

[ptt81]

Originally Posted by BrianG

Not that I can see. As long as the voltage is equal or better than the originals, they were soldered correctly, and they are truly low-ESR types, it'll be fine.

Thanks Brian, yes im pretty sure all specs are better than originals, this is the one i used

http://www.digikey.com/scripts/DkSea...name=P12415-ND

I've just ran it today with Neu 1515 1Y and the temp at end of run after 15 min is about 145 on MM heasink and im geared 22/62, Neu got to 152 though, looks hot for Neu but i was told as long as I kept neu running below 175, it shouldn't be a problem. Would this be a safe setup to be continue running or do you suggest I gear down a bit? i was running 22/68 before but felt I want a bit faster. I also have a 1.5D comming, im wondering if I gear for 45mph, about the same as 22/62 on 1Y, would it make things run hotter or cooler? running strictly on 4s only

[hoovhartid]

Originally Posted by BrianG

It may help. It depends on where the heat is coming from. If it's ripple current caused by the motor, then yes. If it's simply the losses from EFT switching/rdson values, then not so much. That said, it won't hurt to add a coupe/few. The worst that'll happen is it doesn't help.
.

not sure that i can figure out where the heat is coming from, but i'll try the caps.

thanks again man,

jarrad

[BrianG]

Originally Posted by ptt81

...I've just ran it today with Neu 1515 1Y and the temp at end of run after 15 min is about 145 on MM heasink and im geared 22/62, Neu got to 152 though, looks hot for Neu but i was told as long as I kept neu running below 175, it shouldn't be a problem. Would this be a safe setup to be continue running or do you suggest I gear down a bit? i was running 22/68 before but felt I want a bit faster. I also have a 1.5D comming, im wondering if I gear for 45mph, about the same as 22/62 on 1Y, would it make things run hotter or cooler? running strictly on 4s only

Yeah, your motor temp is "OK", but I'd regear to get lower temps if it were me. I'm surprised though, I've geared my 1512 2d on 4s really tall and it never got more than warm.

[BrianG]

Originally Posted by hoovhartid

not sure that i can figure out where the heat is coming from, but i'll try the caps.

thanks again man,

jarrad

Yeah, it would be difficult. Just saying that it may or may not help and why, but no matter what, it won't hurt.