capacitor getting hot

[REVO-DADDY]

Hi below is a copy of an email I sent to Novak. I figure the more info the better. I need to get this fixed ASAP:

I have a HV 6.5 system that I run in my buggy. Last week it shut down mid way through the A main. This week it did the same thing, and I noticed the capacitor was really hot. I put a temp gun to it and it was 180 degrees. The motor and ESC both check out at 100-110 degrees. This is actually my second capacitor, my first one went bad about the 3rd week I owned it and I replaced it with another stock replacement which I soldered. I am running 14/46 gearing on 4s lipos. My internal BEC has not been working either. I’ve been running an RX pack. Not sure if this is related or not. I am in a desperate situation, I had 2nd locked up in my local points series, with 2 DNF’s I’ll be lucky to get third. So any help you can give me would be appreciated. Thanks Steve

[BrianG]

A couple of points:

1) Low-ESR caps are good for 105*C. 180*F is only 82*C, so you're under the limit by a substantial amount. 82*C is not a good thing, but the cap should technically be ok.

2) You can usually tell a bad cap by if the top is bulging. The top should be flat.

3) A hot cap could indeed be the cap being overworked, or simply the ESC heating up and the heat being transferred by the large wire to the cap, or both are getting hot. That said, a hot ESC usually means you are overgeared. If not, then something is placing a heavy load on the ESC; binding drivetrain, worn bearings, vehicle too heavy, etc.

[REVO-DADDY]

Originally Posted by BrianG

A couple of points:

1) Low-ESR caps are good for 105*C. 180*F is only 82*C, so you're under the limit by a substantial amount. 82*C is not a good thing, but the cap should technically be ok.

2) You can usually tell a bad cap by if the top is bulging. The top should be flat.

3) A hot cap could indeed be the cap being overworked, or simply the ESC heating up and the heat being transferred by the large wire to the cap, or both are getting hot. That said, a hot ESC usually means you are overgeared. If not, then something is placing a heavy load on the ESC; binding drivetrain, worn bearings, vehicle too heavy, etc.

OK so the cap should be good. It still looked good to the eye. She is a heavy beast. Maybe I'll lower the gear ratio for this week. I am running on the higher end of the spectrum.

[kvrc]

what buggy are you running? if it is anything but an associated then you are way overgeared. you should be at 10/46 or if you had an associated maybee 12 / 46. i am amazed that your motor and esc arent smoking hot with that gearing.

[REVO-DADDY]

Originally Posted by kvrc

what buggy are you running? if it is anything but an associated then you are way overgeared. you should be at 10/46 or if you had an associated maybee 12 / 46. i am amazed that your motor and esc arent smoking hot with that gearing.

I am running a hyper 8.5, it seems to stay cool, but the motor and esc both have 40 mm fans on them

if you are running a rx batt be sure to unplug the red wire from the ESC ,If you havent done so.

[lincpimp]

Originally Posted by REVO-DADDY

I am running a hyper 8.5, it seems to stay cool, but the motor and esc both have 40 mm fans on them

Damn, you are geared for over 50mph. Drop down to an 11t pinion and you will do 40, and you should be able to ditch the fans. They are the only thing keeping that esc from cooking right now. If they fail and you do not notice that esc will be toast...

Plus you do not need to be doing 50 to win a race. A 10t pinion may be even better, as it should put you around 38mph. Your runtime may even double dropping the gearing, as you must be pulling some amps now...

[kvrc]

no matter where you end up gearing it at dont remove the fans unless you are running in very cool outside temps. i guess if it is around 55f or less where you are running it then i can see it not getting super hot. when you start running it on 80+ degree days you will have heat problems.
with my 6.5 system geared at 10/46 if either my esc or motor fan failed my system would thermal at no more than 8 minutes or so in racing conditions.

[REVO-DADDY]

I actually geared it that way to reduce some of the torque, making it easier to drive. I had not considered run time, good point. I'll drop her down and see!