RC-Monster Forums - 9920 Thermal

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- - 9920 Thermal - Cogging (https://www.rc-monster.com/forum/showthread.php?t=2176)

I had problems with my 9L in my Savage cogging badly when geared 16/49, went to a 52t spur and it got better. You might also have to roll the throttle smoother, I've had that be an issue on a few cars.

Quote:

Originally Posted by BrianG

Hello. I don't have any experience with BL ESC's, but I do with electronics in general and those caps look bad. See how the tops are rounded? That means the electrolyte has expanded. This can be caused by age (usually 5-10 years, sooner if they are run at very close or just over their rated voltage), running a higher voltage than they are rated, or reversing polarity. The "steam" you saw was probably electrolyte gas escaping.

Capacitors are used to either pass a certain range of frequencies, or to smooth out voltage transients for a more constant current and voltage. I don't know of their function in that circuit, but since they are where the battery wires enter, I would guess they are being used to filter out noise entering the battery wires. They are too small to provide the transient function judging by the amperages the controller will require. Either way, they are needed and that is very likely what is causing your problem.

There are two ratings for a cap: voltage and "farads" usually expressed as uF. All I can see in the picture is 516k0, but on the other side, you should see the ratings I'm talking about. Most electronics shops (RadioShack) should carry those if you feel like replacing them - just be sure they are installed correctly. The white stripe denotes the negative lead.

Wow, great post. Thanks for taking the time. I am learning a lot!
50v 470uf
http://www.rustyonline.net/assets/im...aprating02.jpg

The controller is only a couple of weeks old. It couldn't have more than 45 minutes run time on it and It cogged or shut down every time.

I wonder if it was bad to start, or If something else caused it. Anyway, I wouldn't want to replace the caps until I knew why it happened. I hope I can exchange it. I would hate to wait months sending it back to Germany.:020:

Thanks again for the great post!!!

Quote:

Originally Posted by dabid

Good point. If I was really gentle on the throttle I wouldn't cog as bad.

Thanks for the reply!

Quote:

Originally Posted by bigabike

NP.

The caps in the first picture you posted looked like they had rounded tops (especially the upper cap), but now the latest picture above seems to show they are flat (like they are supposed to be). Do you see how the tops are sort of "preforated"? This is so if the gas expands, these areas will split and release the gas without exploding. Do these look like they have been split? I really can't tell now from the pics.

If they are rounded/split, it can't be from excessive voltage as they are rated for 50v. Age is apparently not an issue either. The controller was never attached to the batteries in reverse polarity I suppose? I would think that if that were the case, you'd have a LOT more issues than just a couple of bad caps. I dunno...

Maybe the whole issue is as simple as dabid pointed out, but I don't like the fact that you saw "steam" from the caps at one point...

I hope the solution is simple for your sake.

No REverse Polarity.

Caps don't look split, but 2nd picture had time to cool.

Simple would be nice.

Hey Mike, any ideas?

try emailing mike or sending him a pm he might not see this thread

I would try to move the receiver away from the motor some. Put it back where the atenna is. see if that helps. The steam don't sound good either.

Make sure your batteries are not shorting out on the chassis. I did this on a 7020 and swoll the caps up.

The only thing I happened to notice from the pictures is that the controller has the black BEC jumper intact, which suggests that you are using the controllers BEC. It is in fact rated for 12 cells, but the xl motors can "ask" for a lot of power, which in conjunction with the "heat" generated by the bec could be heating things up pretty badly. Despite the 12 cell rating, it is usually best to run a receiver pack or UBEC when using 8 or more cells, due to the heat generated by the excessive voltage (bec is trying to "get rid of" the extra 8 or so volts). The gearing shouldn't be too far off at all, actually. I would try a receiver pack as the first step.
As for the steam....well I don't know. If the caps vented, that could be considered very bad. If they didn't vent, then steam suggests moisture, which is also considered bad! Try a receiver pack(and remove the controller's bec jumper) and report back.

I tried a reciever pack before the "steam". Cogging and heat were about the same. I took it off replaced the jumper and video taped last night without it. What should I do next?

Look for a short somewhere? was the motor hot, or just the controller?

Quote:

Originally Posted by RC-Monster Mike

Look for a short somewhere? was the motor hot, or just the controller?

Just the controller. Should I hook it back up and see if vents again?

I could use a third set of batteries protected from chassis.

do any of the caps seem to be disconnected? If anything, you are undergeared, not overgeared, so the controller shouldn't be working very hard at all. Got any pictures of the controller mounted in the truck?

Quote:

Originally Posted by RC-Monster Mike

Yes - Here

http://www.rustyonline.net/assets/images/IMG_0319.JPG

lol, join the club of broken escs...