blowing caps 180esc

[ezhitz]

Just a question about the caps on the esc and what causes them to blow?
Just put in a new Hobbywing 180amp after the second run a cap let go I think
the problem was caused by half throttle running as the boat is to unstable at WOT
its in a 1/10 hydro 7XL 4S 5000mah pack spinning a x437.The eagle tree showed a spike 150 amps


http://www.youtube.com/watch?v=OoypEAo1Kbg

[scoota]

i have asked the same question down at the club my self , i will try and explain the best i can , the half throttle will get the fets working over time which will cause the ESC to run hot but not blow the caps .

i was told if you back off from full throttle to a stop , the the caps will have a full charge in them still & as the boat slows down in the water ,the prop starts to turn the motor , causing it to turn into a generator & putting more charge into the caps causing them to blow.

so now insted of coming off full throttle to a stop i run my boat to a gradual stop for a half a lap before bring it back to shore . Since i have been doing this i have not blowen any caps ...

[keithbradley]

i have asked the same question down at the club my self , i will try and explain the best i can , the half throttle will get the fets working over time which will cause the ESC to run hot but not blow the caps .

i was told if you back off from full throttle to a stop , the the caps will have a full charge in them still & as the boat slows down in the water ,the prop starts to turn the motor , causing it to turn into a generator & putting more charge into the caps causing them to blow.

so now insted of coming off full throttle to a stop i run my boat to a gradual stop for a half a lap before bring it back to shore . Since i have been doing this i have not blowen any caps ...

I have to imagine this is happening more commonly with the Asian motors? I cant imagine my prop spinning my Neu's but I could definitely see them spinning the "free-er feeling motors".

[m4a1usr]

I have to imagine this is happening more commonly with the Asian motors? I cant imagine my prop spinning my Neu's but I could definitely see them spinning the "free-er feeling motors".

You are most likely correct. There is absolutely no way the water resistance on a SV27 6 pole motor off the prop is going to rotate the drive line. Its almost impossible to do on the bench using ones big strong mits. Water friction with the prop dia we use in said hull does not have enough force to make that happen.

Now a 2 pole 540 can I can see it happening. At least the possibility. Maybe even some 4 pole motors. Magnet force is weaker, rotor mass is not significant, drivelines are about as free as we desire them to operate at.

No matter how this thread develops you cannot charge the caps far above their rating or capability. Its a matter of design. Your not going to get 60 volts stored on a 30 volt cap. Not for long. It leaks. It self discharges. Its design. So the question really is how far above the rated voltage can a capacitor safely maintain voltage and hold it? And for how long? The problem with ultra low ESR caps is they have been designed with excellent voltage surge characteristics. A weakness so to speak in our ESC designs.

This might develop into a very informative thread providing the right folks speak up.

John

[Steven Vaccaro]

You are most likely correct. There is absolutely no way the water resistance on a SV27 6 pole motor off the prop is going to rotate the drive line. Its almost impossible to do on the bench using ones big strong mits.

John

Thats one of the reasons the sv27r motor is a bit different than the sv27. The sv27 motor acts as a brake, causing handling issues when slowing down.

[Flying Scotsman]

Just a question about the caps on the esc and what causes them to blow?
Just put in a new Hobbywing 180amp after the second run a cap let go I think
the problem was caused by half throttle running as the boat is to unstable at WOT
its in a 1/10 hydro 7XL 4S 5000mah pack spinning a x437.The eagle tree showed a spike 150 amps


http://www.youtube.com/watch?v=OoypEAo1Kbg

First off you are from Ontario.. ..How long was the first run and temperatures, battery depletion etc ....rest time....and time duration etc. before boom on second run.....plus as you have stated your throttle position probably caused the problem....talk to Doby, one of the few bright sparks left in Ontario

Douggie

[ezhitz]

Hi Douggie,Yes Ontario the first run was just over 1 1/2 minutes with temps under 120f
was about ten minutes before went out again.

[Doby]

Whereabouts are you?

I just added an Etti cap board to my 180 Turnigy after the caps had discoloured a bit. Seem to be finenow.

[dasboata]

Whereabouts are you?

I just added an Etti cap board to my 180 Turnigy after the caps had discoloured a bit. Seem to be finenow.

can I see some pics of that and where did you purchase thanks Chris

[785boats]

The problem is even worse if the brake setting is set to ON. Some ESCs apply the brake automaticaly for a few second when the throttle is released if it is switched on.

Insaniac.
The testing has been done by many people. Here's one finding.
Cheers.
Paul.

[scoota]

Running at half throttle places about 50% of the battery power into the ESC and the rest into the motor. The cap blew due to excessive pressure which was caused by excessive heat in the ESC at half throttle.
If however, the cap shorted (high voltage breakdown) rather than exploded, then it was an over voltage problem...interesting comment about the back EMF of the motor-to-generator theory causing the (over voltage) problem...someone should do some tests to verify that!

i guess my generator theory has a bit of fact behind it , thanks to Pauls info

All i can say before i changed the way i brought my my boats to a stop , i was blowing caps on my ESCs all the time , and now it does not happen anymore !!!

The people that i ask these sort of questions to, know there stuff & would not give me an answer unless there was some sort of testing to back there answer!

[Insaniac]

i guess my generator theory has a bit of fact behind it , thanks to Pauls info

All i can say before i changed the way i brought my my boats to a stop , i was blowing caps on my ESCs all the time , and now it does not happen anymore !!!

The people that i ask these sort of questions to, know there stuff & would not give me an answer unless there was some sort of testing to back there answer!

Or it could be that by gradually backing off the throttle you are slowly discharging the capacitors rather than abruptly chopping the throttle (ESC rapidly reduces voltage across caps to zero causing rapid discharge and failure).
It just seems hard to believe that there is enough torque created by the water flow to spin the motor against the resistance of the magnets-at least in my motors the force required to turn the shaft is significant).
JMHO

[ezhitz]

Hi Doby I'm in Brampton I will add a couple of caps to try it on the weekend and order
a Etti cap board for it.

[detox]

Prop appeared to be cavitating. Hull should jump on plane quicker than that. Lower the strut deeper into water and set to neutral. Maybe over cavitation caused it?


...

[BakedMopar]

I have the caps on mine and they have been working pretty well. They have dropped my cap temp over 15 degrees.

What size hull is that?

[785boats]

ezhitz.
There are a few other things that can cause caps to blow.


High resistance connectors between batteries & ESC including faulty solder joints.
Cables too long between battery & ESC.
Cables too small between battery & ESC.
Batteries not big enough to be able to supply the load the motor demands. including peak loads.
Brake setting on
Hard startup mode programmed in the ESC. Select Soft start. Its easier on the ESC.
Too little or too much timing programmed into the ESC. That 7Xl likes between 7 & 15 degrees. I run all my 2 pole Xl motors at 15 degrees.

Any one or a combination of 2 or more of those things can pop caps.
Of course it could have just been a faulty cap.

I know there are more reasons but I can't think of them right now.

Cheers.
Paul.

[ezhitz]

Thanks guys for your answers I know not seeing things first hand can only lead to a educated guess thats what great about this forum and all the vast knowledge somebody else probably already experienced it.
The esc was set forward only and 11.25 degrees timing running 4S 5000mah turnigy with 5.5 bullet connector.

Thanks Jack

[properchopper]

Just a question about the caps on the esc and what causes them to blow?
Just put in a new Hobbywing 180amp after the second run a cap let go I think
the problem was caused by half throttle running as the boat is to unstable at WOT
its in a 1/10 hydro 7XL 4S 5000mah pack spinning a x437.The eagle tree showed a spike 150 amps


http://www.youtube.com/watch?v=OoypEAo1Kbg

I am the only one that's picking up on the fact that a 7XL in a 30" boat, even with that small prop, is a bad choice ? 7XL's are usually used for 4S SAW riggers & such. I would run a 9XL ; in fact I often ran one in the 31" H&M that George now has and it was fast & ran a long time on 4S2P.

Just re-did my Vegas with a 180, added an Etti cap bank, like most of my high perf rigs. Or you can get Rubicon caps [ 1500 uF, 25V] from Newark Electronics for $5.67 for ten. ( I just did).

[dasboata]

I am the only one that's picking up on the fact that a 7XL in a 30" boat, even with that small prop, is a bad choice ? 7XL's are usually used for 4S SAW riggers & such. I would run a 9XL ; in fact I often ran one in the 31" H&M that George now has and it was fast & ran a long time on 4S2P.

Just re-did my Vegas with a 180, added an Etti cap bank, like most of my high perf rigs. Or you can get Rubicon caps [ 1500 uF, 25V] from Newark Electronics for $5.67 for ten. ( I just did).

Properchopper I am going to use the way you hooked up the ETTI caps. Looks like you just stripped the battery leads and soldered them to the board is there anything else I need to know thanks chris

[BakedMopar]

I was thinking the same thing Tony. Thats why I asked for the size of the hull. OTOH I have been running an 8xl with a 120 for now until my 9xl comes. I have been running it with a ABC 1.6/3 and a x442 and temps are around 120 ish. I just want longer run times and cooler temps. If I didn't get the deal I did on that 9xl I would of bought a 10xl.

[ezhitz]

Yea Tony I know the motor is the problem Its really my sons boat and I said the 9Xl would of been better but he didn't listen whats the old man know .He just ordered from offshore a leopard 4074 2000kv to try in it.

[scoota]

more tests that show a brussless motor can be turned into a GENERATOR

http://www.youtube.com/watch?v=1thlL...=youtube_gdata

[JackBlack26]

more tests that show a brussless motor can be turned into a GENERATOR

http://www.youtube.com/watch?v=1thlL...=youtube_gdata

The only difference between a generator and a motor is the supplied power to create ether. Spin the motor shaft and you get a generator producing power at the motor leads. Provide power to the leads and you get a motor. Internally both are the same, stator(windings)/rotor.

There is always great info on this site about caps. I love reading it.

Thanks to all that have contributed

[Insaniac]

The only difference between a generator and a motor is the supplied power to create ether. Spin the motor shaft and you get a generator producing power at the motor leads. Provide power to the leads and you get a motor. Internally both are the same, stator(windings)/rotor.

There is always great info on this site about caps. I love reading it.

Thanks to all that have contributed

You missed the point...again...there is not enough prop "torque" when you slow down to rotate the motor/drive shaft against the resistance of the magnets in most brushless motors. The only exception that I own is the Ammo 36-50-2300 which spins freely...

[sundog]

there is not enough prop "torque" when you slow down to rotate the motor/drive shaft against the resistance of the magnets in most brushless motors. The only exception that I own is the Ammo 36-50-2300 which spins freely...

But when at speed and initially slowing down there is plenty enough torque from a prop in water to turn even a high cogging motor. Never underestimate the power of water

[JackBlack26]

You missed the point...again...there is not enough prop "torque" when you slow down to rotate the motor/drive shaft against the resistance of the magnets in most brushless motors. The only exception that I own is the Ammo 36-50-2300 which spins freely...

Please explain how I missed the point? In the post you quoted I was explaining that a motor and a generator are the same in design. The difference is which end they are powered from. I never said, or agreed, that was the reason for caps blowing!WTH does that have to do with you and the motors you own? I understand your point that other than some cheap 2 pole motors most quality 4 pole motors, and higher, wont spin the prop just from forward momentum due to magnet strength. Stating that "I missed the point" when I never disagreed with you is a bit off!

Come to think of it, I don't even see why this topic is an issue in Rc boats unless these ESCs don't have reverse circuitry protection. I raced 1/8 scale electric buggies and truggies for over a year running Neu and Castle motors and never had an issue blowing caps when off throttle and the cars were still in motion, coasting with the motor still spinning.

[bigwaveohs]

Please explain how I missed the point? In the post you quoted I was explaining that a motor and a generator are the same in design. The difference is which end they are powered from. I never said, or agreed, that was the reason for caps blowing!WTH does that have to do with you and the motors you own? I understand your point that other than some cheap 2 pole motors most quality 4 pole motors, and higher, wont spin the prop just from forward momentum due to magnet strength. Stating that "I missed the point" when I never disagreed with you is a bit off!

Come to think of it, I don't even see why this topic is an issue in Rc boats unless these ESCs don't have reverse circuitry protection. I raced 1/8 scale electric buggies and truggies for over a year running Neu and Castle motors and never had an issue blowing caps when off throttle and the cars were still in motion, coasting with the motor still spinning.

A theory put forward in this thread is that when the throttle is quickly chopped to zero, the water would spin the prop in reverse creating a generator effect which caused the resulting (over?) voltage to blow the capacitors. Insaniac simply stated that he didn't agree that this was the cause because most motors have magnets that are strong enough to prevent the motor shaft/prop from spinning simply due to the water flow as the boat slows down.

BTW, I no longer provide "advice" on this forum...guess why...

[ray schrauwen]

Just a question about the caps on the esc and what causes them to blow?
Just put in a new Hobbywing 180amp after the second run a cap let go I think
the problem was caused by half throttle running as the boat is to unstable at WOT
its in a 1/10 hydro 7XL 4S 5000mah pack spinning a x437.The eagle tree showed a spike 150 amps


http://www.youtube.com/watch?v=OoypEAo1Kbg

Who makes the 7xl ? it is a 2 pole motor which is not so easy to run on a Turnigy 180. Standard timing is a bit high for a 2 pole motor BUT, sometimes caps are crap.

Thats all, sometimes there are bad ones from the factory. In fact there are allot of Capacitor failures due to some poor manufacturing & poor quality raw materials.

Do research, The Cap King has great information on what is good and not so good. He also has a great slection of low ESR caps.

[ScarabChris]

Is it bad to run these ESCs at low or half throttle for any period of time? Because sometimes I just like to put the boat in the canal behind my house and tool around.

[ray schrauwen]

It partly depends on how hot your setup is but, in general, the ESC is working much harder at 1/2 throttle.