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Over heated Capacitors on ESC

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Old 07-24-2019, 01:33 AM
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Aashoj
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Smile Over heated Capacitors on ESC

Hi everyone,
I'm new in these forum and in the RC electric world and have a issue with my Capacitors on my ESC is over heated and melting the wrap around them and make lot of smoke in my boat.

I run with 4S 30C Battery and it should could run with up to 6S. The cable from ESC and up to motor is also extreme hot include the battery.
What are I dimension wrong? hope someone have help with a good idea?

Here are the spec on the motor/ESC kit I bought:
Specifications:
Weight: 356 g
Type: RC model part and accessories.
Engine specification:
Brand: Rocket.
Model: 2958
Item name: brushless motor.
Material: metal + magnet.
KV (RPM / Volt): 3380 kV
RPM: 60000.
Wattage: 1400 watts
No load current: 1.9 A.
Maximum voltage: 18 V.
Diameter: approx. 29 mm / 1.14 inches.
Length: approx. 58 mm / 2.28 inches.
Shaft diameter: approx. 3.175 mm / 0.13 inches.
Fit: for RC boat 600 - 800 mm.
Connection: 4 mm golden banana connector.
ESC Specification:
Brand: Rocket.
Item Name: 70A Brushless Regulator with 5.5V/3A BEC
Cont. Current: 70A.
Shock current: 90A (10s).
Voltage: 5-18 NC / 2-6 LiPo
Program: yes.
BEC: 5.5 V / 3A
Item size: approx. 80 x 50 x 23 mm / 3.15 x 1.97 x 0.91 inches.
Water cooling jacket specifications:
Item name: 29-S water cooling jacket.
Material: aluminium
Colour: black
Developed for: 2958 2948 RC brushless motor
Outlet Hole Diameter: Approx. 4.5 mm / 0.18 inches.
Coat diameter: approx. 29 mm / 1.14 inches.
Outer diameter: approx. 37 mm / 1.46 inches.
Coat length: 47 mm / 1.85 inches.
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Old 07-24-2019, 02:09 AM
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Okay, let's throw out more information. What are/is the:
1) Boat size
2) Boat weight
3) Prop Number
It sounds to me like you're overloading the motor and, indirectly, the ESC. It could even be drag from the drive line rubbing on the stuffing box
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Old 07-24-2019, 05:03 AM
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Originally Posted by Hydro Junkie View Post
Okay, let's throw out more information. What are/is the:
1) Boat size
2) Boat weight
3) Prop Number
It sounds to me like you're overloading the motor and, indirectly, the ESC. It could even be drag from the drive line rubbing on the stuffing box

I use a 60 cm/24" catamaran, weight 1,1 kg, 38 mm/1,5" - rate 1:4 prop
Maybe i also do something wrong, because My Transmitter have 3 power level and I use level 2, and do not exactly know how it adjust the power?
When I run 2S it is very slow and with 4S is to mush. So when running with 4S, I have to adjust my receiver to power level 2 and now it run fast, but I can handle the boat. Full power, it goes out of water and nearly fly!

I will order 3S and try these, but just need to be sure about these overheating. I have made double water coiling so my my motor and ESC is not hot at all!

Last edited by Aashoj; 07-24-2019 at 06:14 AM.
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Old 07-24-2019, 06:36 PM
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The OP has several issues contributing to his overheating:

1) He is using the wrong motor, the Kv is too high for 4S, it is more suitable for 3S but still high. A Kv of 1800-2200 would be suitable for his model on 4S.

2) Running the boat extensively at part throttle is VERY hard on the ESC and will overheat it. The hotter the setup the worse the overheating will be.

3) The battery is inadequate, today a 30C battery has excessive internal resistance, that is one reason the battery is hot.

4). The power wires to the ESC may be too long/too small in diameter. Or the connectors may have too high resistance. Or both.

5) The caps are hot because the battery cannot supply enough current under high load, this is most commonly caused by long/thin battery wires or weak batteries, or both.

The simplest solution for the OP is to try a larger prop on 2S with his current setup. And reset the transmitter to give full throttle, remembering to avoid excessive part throttle running.


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Old 07-24-2019, 10:13 PM
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Thanks for these extreme informative information, is really tell a lot of what to do. I have also read the Treat at the top now and can see i made lot off mistake.
I buy a "Ready to run boat" Volantex Atomic and it run well, but they have mount a 20A ESC in still off a 40A like the wrote is standard. Both the motor and ESC burn out after just 3 runs.But buy it true Banggood who are a Chinese site and they are very difficult to tell anything.
I sent pictures and they feedback ones and wont video and never from from them again.
That was the reason I buy these complete motor kit, before i Know anything about "KV" and combination between motor - ESS - Battery. But in the description the wrote from 2 - 6S battery, but can see now is totally wrong set-up!

I have bought a new boat, a Genesis Offshore Brushless RC Twin Hull and now really afraid for I have do in my pants one time more, but that must bee in a new tread i will ask about these, before first running!

Last edited by Aashoj; 07-24-2019 at 10:20 PM.
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Old 07-25-2019, 12:16 PM
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Originally Posted by Got RPM View Post
The OP has several issues contributing to his overheating:

1) He is using the wrong motor, the Kv is too high for 4S, it is more suitable for 3S but still high. A Kv of 1800-2200 would be suitable for his model on 4S.

2) Running the boat extensively at part throttle is VERY hard on the ESC and will overheat it. The hotter the setup the worse the overheating will be.

3) The battery is inadequate, today a 30C battery has excessive internal resistance, that is one reason the battery is hot.

4). The power wires to the ESC may be too long/too small in diameter. Or the connectors may have too high resistance. Or both.

5) The caps are hot because the battery cannot supply enough current under high load, this is most commonly caused by long/thin battery wires or weak batteries, or both.

The simplest solution for the OP is to try a larger prop on 2S with his current setup. And reset the transmitter to give full throttle, remembering to avoid excessive part throttle running.


.
I have now try with a 42 mm prop and only 2S battery, I calibrate mt throttle with ESC and it sims like it work gut. I test the boat and run out on water, but when i give throttle, the motor set out and in 3 -4 times and are so dead.
I pick up the both and could see there was no light on the receiver. I took the battery off and put on again and now it lighten up and work again until i give it throttle and so it was same history.

Is there someone who have a idea what the can be?

Last edited by Aashoj; 07-25-2019 at 09:29 PM.
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Old 07-25-2019, 02:35 PM
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It sounds like the ESC is shutting down due to low voltage, with weak packs the inout voltage could be low enough to trigger the LVC, even if fully charged.

My last club ran a similar motor (36mm, 3500 Kv) in small (25”-28”) hydros with Octura m440 props on 2S and got speeds in the mid to high 40s. Your cat won’t go that fast on 2S but should still be plenty.


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Old 07-25-2019, 11:17 PM
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Originally Posted by Got RPM View Post
It sounds like the ESC is shutting down due to low voltage, with weak packs the inout voltage could be low enough to trigger the LVC, even if fully charged.

My last club ran a similar motor (36mm, 3500 Kv) in small (25”-28”) hydros with Octura m440 props on 2S and got speeds in the mid to high 40s. Your cat won’t go that fast on 2S but should still be plenty.


.
Thanks Got RPM,

After read your information and looks at some Youtube video, I can see that kit is useless! Why in hell are they sell kit like these for boat in 24 - 31"?
There are following a 70A ESC with the motor and the best rpm IS 20 - 35000 rpm and after some calculating I can not get the right setup!

2S battery will give about 28000 rpm but use 166A
3S battery will give about 42250 rpm and use 121A
4S battery will give about 56108 rpm and use 84A

If I have understand it correct you take your motor Watts and divided it with the battery volts and so you got you amps?
And the RPM you got with divide the KV with the Volts?

So when the ESC only is on 70A it will never could be use for these setup or??

You can by these kit anywhere on Ebay and Amazon?

If I understand it correct, I have the right RPM with the 2S battery but I have to buy a minimum 200A ESC to get run with a little bit overcapacity, right?
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Old 07-27-2019, 09:03 AM
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I’m not certain how you calculated amps but it is incorrect. Higher voltage applied to this setup will give higher amps, not lower. You cannot use the motor’s “rated watts” to calculate amps, that value is pretty meaningless and is more marketing than reality. The amp draw is based on the load (prop) and how the boat is set up and driven, not on theoretical math based on fake facts. The Kv x volts again gives a theoretical rpm without load, under load the rpm will decrease.

That motor on 2S should draw around 20-40 amps if correctly propped. It is a small cheap motor and won’t handle more without damage.
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Old 07-28-2019, 11:26 AM
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Originally Posted by Got RPM View Post
I’m not certain how you calculated amps but it is incorrect. Higher voltage applied to this setup will give higher amps, not lower. You cannot use the motor’s “rated watts” to calculate amps, that value is pretty meaningless and is more marketing than reality. The amp draw is based on the load (prop) and how the boat is set up and driven, not on theoretical math based on fake facts. The Kv x volts again gives a theoretical rpm without load, under load the rpm will decrease.

That motor on 2S should draw around 20-40 amps if correctly propped. It is a small cheap motor and won’t handle more without damage.
Thanks for help, I still have mush to lean!
I got my info for a Youtube video i watch: Matching Motor, ESC, & Battery, : www.youtube.com/watch?v=LlSa2f76QiU&t=344s

When I test the Motor up against my transmitter with 2S, without install prob-shaft it start and run great from low rpm and up. But if i install shaft or just gentle lay a finger on the motor axles it will not run. The motor have big problems to start running, but if first start running, it have no problems.

I have calibrate it with my Transmitter, what can be wrong?
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Old 07-29-2019, 07:49 AM
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Assuming the transmitter and ESC are correctly calibrated, if the motor won’t run under any load, then it is most likely damaged or broken. An opportunity to install a more appropriate motor.
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Old 08-18-2019, 09:22 PM
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Thanks Got RPM,
Just got home from hollyday, i wil try to change motor or ESC.
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Old 09-05-2019, 06:00 AM
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Default Where purchase props

Where is the best place to purchase these boat props?
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Old 10-07-2019, 10:06 PM
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Originally Posted by Got RPM View Post
Assuming the transmitter and ESC are correctly calibrated, if the motor won’t run under any load, then it is most likely damaged or broken. An opportunity to install a more appropriate motor.
Sorry for let feedback.

It was my ESC who was burn off and after changed that It run perfect. I try out with 2-cell and a bigger prop and it turn out good, but a bit to hot. I now changed to a smaller 38 mm prop and 3-cell and it look like it perform x-stream well!
Run fast, but can still handle it and are not over heated.
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Old 10-10-2019, 12:57 AM
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I'm not into fast boats, but have spent some quality time with capacitors.
Generally, if an electrolytic capacitor is run within its rated volage, it will not heat up. If it is run at or below its rated ambient temperature, it will not heat up. If it heats up, the liquid electrolyte expands and eventually escapes. A capacitor trying to stabilize an ESC supply is receiving volts from both the battery and from the back emf of the motor. If the back emf spikes do not have a short path to the battery, they are collected by the capacitor. Back emf spikes can be considerably more than the battery voltage.
Electrolytics are very poor at handling high frequencies, which includes sudden voltage spikes. Most data sheets for voltage regulators recommend fitting a fairly low value dsc ceramic capacitor across the large value electrolytic. Because of the way that they are built, electrolytics have quite high inductance, the more capacity, the more inductance, hence the need for a capacitor in parallel with good RF rating. That, and short, heavy battery leads.
If the electrolytic is being heated by components inside the ESC, either radiated heat or conducted by the leads, that is a different problem leading to the same result.
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