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Old May 15, 2006, 07:28 PM
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My lipo on fire!!! Align ESC Help please!

Ok everyone so i am running a 3550 align kv motor with a 35 amp esc. I have a 2200 mah battery with a 10c const. Discharge rate. My problem occured when i was just spooling my heli up (with the batt. on the ground luckyly) and the first battery went dead after about 8 minutes of just checking stuff. No liftoff. And then i let the heli cool. Than i hooked up the 2200 mah 10c constant battery and out of nowhere it cought on fire!!! I quickly put it out. The polaritys were correct and everything! I had the ESC programmed to slow brake. High motor speed. And high discharge. I dont know if this was the problem or what was. If it was the ESC programming please let me know what i should program it for. please help me so i dont screw up another ESC, Motor, and battery. I was fortunate to get them replaced this time! Thanks a lot...

Todd
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Old May 15, 2006, 07:32 PM
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First off, no brake on helis.
Second 10C discharge pack and a Trex aren't going to play very well.
Third, high discharge isn't that great an idea, gives you not much margin of safety in situations like this.

This may not matter though, as there are a ton of variables that can make this stuff happen. The battery probably made fire because you drew too much current out of it. What is causing this is what you need to determine. Possible causes :
Gear mesh too tight.
Binding in the tail drive shaft
Belt too tight
Messed up motor
Badly set throttle/pitch curves
Battery simply isn't up to delivering the current you are asking. 10C battery isn't a good start.
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Old May 15, 2006, 07:39 PM
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with the align 430L you need at LEAST 15c @ 2200mAH capacity
it's a 30-35amp motor run on a 13t pinion.

15c apex mk3's dont even cut it if youre pushing the trex hard.
20c's seem to work fine.
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Old May 15, 2006, 08:49 PM
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Vince Herman's Avatar
United States, OH, Strongsville
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Add to Koko76's lst of alternative reasons for over-current:

Pinion too large
lock-tite on a bearing (don't ask me how I know)
tail blades in the weeds ( )
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Old May 16, 2006, 03:39 AM
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Akershus, Norway
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Quote:
Originally Posted by jh4db536
with the align 430L you need at LEAST 15c @ 2200mAH capacity
it's a 30-35amp motor run on a 13t pinion.

15c apex mk3's dont even cut it if youre pushing the trex hard.
20c's seem to work fine.
Obviously this is not the problem in this case as those values are only the extremes and this guy has not lifted off the ground yet.

But I agree, that motor requires a much better battery to perform well.
I'd say at least able to deliver 30A constant.

I guess by high motor speed you mean high timing. Don't use this. That motor is suited for mid-timing and this might be one of the reasons for exessive current draw in addition to the reasons mentioned. You should be able to hover/FF with that motor at an average of 8-9 A.
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Old May 16, 2006, 07:10 AM
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My personal suspicion is that having the brake set might cause issues... I guess the ESC is going to actively try to brake the head (i.e. draw power from the pack to do this) and even a slow brake is gonna need quite some juice.
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Old May 16, 2006, 08:02 AM
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You sure? Some electric cars actually charge when braking. Trains can do the same (well not charge but produce electricity)

But yeah, if it's not done in any smart way it can be compared to a fairly hard climb-out.
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Old May 16, 2006, 08:09 AM
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I am almost positive when he said "slow brake" he meant "slow start," and it just came out wrong. I bet braking is disabled.
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Old May 16, 2006, 09:36 AM
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Quote:
Originally Posted by koko76
First off, no brake on helis.
Second 10C discharge pack and a Trex aren't going to play very well.
Third, high discharge isn't that great an idea, gives you not much margin of safety in situations like this.

This may not matter though, as there are a ton of variables that can make this stuff happen. The battery probably made fire because you drew too much current out of it. What is causing this is what you need to determine. Possible causes :
Gear mesh too tight.
Binding in the tail drive shaft
Belt too tight
Messed up motor
Badly set throttle/pitch curves
Battery simply isn't up to delivering the current you are asking. 10C battery isn't a good start.
I think NONE of this reasons could have created the fire. if you have a bad setup, the heli simply wonīt fly.

A 10C battery might be too low for a T-rex, but I donīt think this itīs the reason. A 10C battery wonīt letyou fly 3D and the flight time will be short, but it for shure will letyou hover.

for a lipo to get in fire, it has to puff and smell before fire; not suddenly.
Live2die420 : maybe you didnīt nottice a puffed cell or a strange smell. the fire was created due to a damaged cell; maybe the cell was overdischarged or overcharged. The root of this fire can be the battery was out of balance, and you recharged the battery over and over without balancing it.

Do you have a lipo balancer...???
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Old May 16, 2006, 10:09 AM
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Quote:
Originally Posted by luis104
I think NONE of this reasons could have created the fire. if you have a bad setup, the heli simply wonīt fly.
Well, this is simply not true, there are certainly conditions that would cause these batteries to overdischarge at rates beyond what they are capable of in flight. That being said, his heli DID NOT fly, he said he only spooled it up.
That list was not all inclusive by any means, but to even begin to approach using these cells in this application, you need to make sure you are drawing the lowest level of current possible. With a bad gearing setup, binding belt drive etc you can certainly draw beyond what the cells can handle.
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Old May 16, 2006, 10:54 AM
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Quote:
Originally Posted by Tintin
You sure? Some electric cars actually charge when braking. Trains can do the same (well not charge but produce electricity)

But yeah, if it's not done in any smart way it can be compared to a fairly hard climb-out.
No way Tintin.... at least not IMO. You're asking a heck of a lot of a brushless ESC to have it put power back into a LiPo - correct voltage, less than 1C (when it does not KNOW the C) on the fly.

The only way I can see a brake working is by using power and having the ESC 'drive' the motor backwards. If someone knows better then I'd be happy to be educated... always good to learn how these things actually work
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Old May 16, 2006, 11:03 AM
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It's called regenerative breaking. Essentially the motor becomes a generator similar to how your alternator works on a real car. Most esc's just disregard the power generated when the motor is slowing down.

The motor doesn't have to be spinning backwards, just spinning. I don't know much more than this but it's one of the ways a hybrid/electric vehicle gains efficiency.

Blake
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Old May 16, 2006, 11:15 AM
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I didn't mean it would charge but thought it might just burn off the amps.
When you load a motor it draws amps, to brake it you just need to apply resistance, you don't really need to run a lot of current backwards if I remeber my electronics class at all...
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Old May 16, 2006, 11:19 AM
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I did not mean to imply that the motor spins backwards - just that the ESC applies power to the coils such that the 'drive' is reversed.

Whatever, just a theory - brake on heli bad. Too much energy in the head.
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Old May 16, 2006, 11:25 AM
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agreed...
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