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Potential battery problem concern question

Old 10-15-2019, 08:15 PM
  #1  
Albatross1
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Smile Potential battery problem concern question

Hi Everybody,

Recently burnout of a motor badly affected an ESC so any help understanding that and battery affects would be greatly appreciated

After rebuilding a Skipper plane and testing it well, it seemed to be in good condition but eventually the motor burned out (and smoked!) but that also seems to have damaged its ESC. The ESC seemed fine because all of the servos still worked well but the next motor in another plane also burned out too. It seems that the ESC has two separate control portions that are not directly connected to each other

In that ESC damaged condition, could it also damage or affect the LiPo battery that was providing power when the motor burned out?

Basically, the batteries seem fine and the following ones have been connected to the ESC that failed (and one of the 3S was connected when each of the two motors got burned out):

- the 2S batteries have cells at 4.13 V and 4.12 V, 94% or another battery with cells at 4.13 V and 4.12 V, 94%

- the 3S batteries have cells at 4.06 V; 4.06 V and 4.06V, 85% or another battery with cells at 4.18 V; 4.18 V and 4.18 V, 99%

Although the batteries still seem pretty balanced and good, could they damage another good ESC or Motor?

best regards,
Dave

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Old 10-18-2019, 09:41 AM
  #2  
mkjohnston
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Dave, I don't mess with lipos for this reason. There are set procedures when you charge them and if you don't follow that you will have a meltdown or even a fire. I went to an RC track in NW Houston Texas a few years back and there was a RC car on fire outside the pits. The guy told me that it was ESC that was on fire and that it was so hot it actually burned the chassis.You are lucky your airplane did catch on fire.
Michael
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Old 10-23-2019, 05:01 PM
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ticedoff8
 
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Originally Posted by Albatross1 View Post
Hi Everybody,

Recently burnout of a motor badly affected an ESC so any help understanding that and battery affects would be greatly appreciated

After rebuilding a Skipper plane and testing it well, it seemed to be in good condition but eventually the motor burned out (and smoked!) but that also seems to have damaged its ESC. The ESC seemed fine because all of the servos still worked well but the next motor in another plane also burned out too. It seems that the ESC has two separate control portions that are not directly connected to each other

In that ESC damaged condition, could it also damage or affect the LiPo battery that was providing power when the motor burned out?

Basically, the batteries seem fine and the following ones have been connected to the ESC that failed (and one of the 3S was connected when each of the two motors got burned out):

- the 2S batteries have cells at 4.13 V and 4.12 V, 94% or another battery with cells at 4.13 V and 4.12 V, 94%

- the 3S batteries have cells at 4.06 V; 4.06 V and 4.06V, 85% or another battery with cells at 4.18 V; 4.18 V and 4.18 V, 99%

Although the batteries still seem pretty balanced and good, could they damage another good ESC or Motor?

best regards,
Dave









What you are describing is a problem with the ESC - not a LiPo battery problem.
It would be more accurate for someone to say "That's why I don't mess with brushless motors" than to be afraid of LiPo batteries.

In your "ESC", there are two (basically) separate sections (circuits) in the same housing being called an "ESC":
* Electronic Speed Controller (ESC) which takes DC power from the LiPo battery and, using a microprocessor controlled power circuit, converts it into AC pulses that control the 3 phases of the brushless motor
* A Battery Elimination Circuit (BEC) regulates the high voltage (8.4v for 2S and 12.6 for 3S) from the LiPo battery down to the DC voltage (4.8v to 6v) needed for the radio and servos
These could be purchased individually as separate devices.
But, for convenience, ESC / BEC manufacturers (EG: Castle Creations Talon vs Edge) will combine them into one device you calling an "ESC". In technical terms, it is a ECS with a built-in BEC.

It sounds like the ESC section has gone bad (the motor burned up) while the BEC section is still ok (your radio still worked) in your ESC with the built-in BEC.
You cannot fix the ECS or BEC sections individually, so it is time for a new ESC with a built-in BEC.

When one leg of the three legs leading to the brushless motor goes bad in the control circuit, you can burn up the motor too. And, you could see a scorched area on the ESC that also overheated. And, the BEC could still function.
You are lucky that the failed ESC section didn't catch the airplane on fire.

It is pretty much impossible that the LiPo was the cause. From the cell voltages you listed, they all look normal.

Back in the day, at our flying field, we would see at least one helicopter per month whose ESC would burst into flames and consume the entire airframe and catch the surrounding grass on fire.
It was one specific manufacturer's ESC and it was due to their design of output circuit in the ESC.
They discontinued that ESC and the next model had a better circuit that didn't catch on fire.

For your next ESC, I highly recommend Castle Creations.
I use their ESC and BEC in my heli. But, I don't use ESC / BEC combos. I use an ESC and a separate BEC.
And, there is no reason to be afraid of LiPo batteries.

Last edited by ticedoff8; 10-23-2019 at 05:19 PM.
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Old 10-23-2019, 05:43 PM
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Very well said ticedoff8 , you explained that perfectly
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Old 10-29-2019, 08:32 PM
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Hi guys,

Hallelujah!! Thank you so much ticedoff8 for the very clear and helpful explanation of that . Init4fun, your confirmation of that understanding is also much appreciated . Thanks for Michaelís comment too about the need for LiPo battery caution ... mine are only charged gently through the small balance leads.

It makes a lot of sense that the motor ESC converts the DC battery to an AC power for the motor while the separate BEC circuit powers the receiver and servos ... and the batteries seem to be ok 👍 woohoo ... a little bravery might be needed to try them again though

Itís interesting that the ESC portion must have been damaged when it was tried with a motor that was in an earlier accident. Then, after that motor shorted out it also damaged the ESC ... so when motors are burned out, should the ESC always be a write-off (?), I guess so. The ESC motor connection could be cut off to be used only for BEC but the need for surgery makes its future dicey The failed ESC portion is a Hitec one that has now been discontinued but the Castle Creations one should be good 👍

Cheers,
Dave

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Old 10-29-2019, 10:50 PM
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... so when motors are burned out, should the ESC always be a write-off (?),
It depends.
Some brand's ESC with built-in BEC are pretty robust and built to protect themselves in the event of a motor failure.
Some - less so.

The problem crops up when one of the output transistors dies.
When that happens, the LiPo battery is effectively directly connected to one set of the motor's coils.
Like a short circuit in the house, this will (literally) burn out a wire in the motor and may cause the ESC to catch on fire.
The original damaged motor could have been what caused the ECS to initially fail. Maybe it stalled while at 100% power. Or overheated. Or the metal can shorted against a coil wire.
But, once the ESC was damaged, plugging in the 2nd (good) motor cause that motor to fail.

Personally, I would trash the bad ESC and not worry about trying to reuse the "spare" BEC.
It may be a ticking time bomb waiting to fail at some point in the future.

As for future use of the 2S & 3S LiPo batteries, they should be ok.
As long as they are not physically damaged, they are pretty tough.

For helicopters, I've heard terms for LiPo pack damage like:
Taco (the pack is bent around such that it looks similar to a taco-shell). This is really bad. Watch for smoke.
Banana (slightly bent) - if it isn't smoking and it tales a charge, we fly it.
Pug (looks like a Pug dog's nose - flat - like the dog hit a wall going 50mph) - This can be worse than a taco. Best to take it out of what's left of the airframe as quick as you can and set it on a concrete pad away from anything flammable. Fireworks will commence shortly.

Last edited by ticedoff8; 10-29-2019 at 11:01 PM.
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Old 10-31-2019, 11:21 AM
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Hi ticedoff8,

hah, hah, yeah thanks again for your great advice . The key hard lesson in this experience is to dispose of a damaged ESC or motor ... to avoid it’s damage propagation.

Hah, fortunately the banana, taco and pug LiPo’s haven’t been experienced but gradual swelling has been had. After the swelling grows a bit they get discharged and disposed of but some folks keep them until they are super-swollen (looking like sausages!). The Taco, Banana and Pug must be pretty amazing

Better safe than sorry applies to the LiPo’s, ... ESC and motor too .

Cheers,
Dave
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Old 10-31-2019, 03:34 PM
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The bad news is that swelling indicates you charging them too quickly and/or pulling more current out than they are designed for.
The C-rating labeled on the pack is pure and unadulterated BS. Unfortunately, the brand and price are also no indications of quality.
Good Luck
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