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Old Apr 07, 2012, 11:19 AM
Registered User
United States, MI, Davison
Joined Feb 2012
46 Posts
Help!
Wrong battery sent to me, Can i still use it?

I ordered a 2200mah 11.1v 20c battery and they sent me a 2200mah 14.8v 25c battery. I am running this motor on 2 of my planes:

http://www.hobbyking.com/hobbyking/s...idProduct=2104

I have tried to find and understand info on these lipo batteries and could not come up with anything that I could understand. So I turn to the experts here in hope that someone could explain this to me.

I have 1- 11.1v 2200mah 20c and now 1- 2200mah 14.8v 25c battery. Will both work with this motor and witch one is better?

Thanks...

BTW I am running a 50A ESC
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Last edited by bigfoot216; Apr 07, 2012 at 01:14 PM. Reason: Providing More information
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Old Apr 07, 2012, 11:40 AM
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Canada, NS, Truro
Joined Aug 2004
292 Posts
Battery

The new battery you got is a 4 cell pack (4S). The motor spec calls for a 3 cell (3S). That means that you would be exceeding the spec voltage by almost 30%. Probably not a good idea. You may burn out motor and ESC and could possibly lose your plane as well.
Charles.
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Old Apr 07, 2012, 11:51 AM
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
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Provided that your ESC is up to it you could technically use the 4S pack with the motor and it would be fine, but it would require you to run a significantly smaller prop and that's probably not the best option. Stick to using 3S packs.

You can probably find someone around here who'd be willing to trade you a good 2200mAh 3S lipo for the 4S one you got by mistake, or you could sell it in the classifieds. Since you only ordered a 3S 2200mAh 20C pack, the 4S is most likely worth more than you paid for it. You could actually come out ahead.
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Old Apr 07, 2012, 01:13 PM
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United States, MI, Davison
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Well I actually went big on the ESC. I bought a 50A ESC for both planes. I should have put that on my original post. Edited now^^.....
So with the large Esc will I be ok?
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Old Apr 07, 2012, 01:30 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
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Quote:
Originally Posted by bigfoot216 View Post
Well I actually went big on the ESC. I bought a 50A ESC for both planes. I should have put that on my original post. Edited now^^.....
So with the large Esc will I be ok?
It's not just the ESC's current rating. Check it is still suitable for a 4s battery, as the BEC may be limited to only a 3s if it has one fitted.

Another point. The 4s will weigh more, so the planes CG will not be correct if fitted where a 3s should go.

You would need to specify all the bits and pieces involved, otherwise it's just guesswork on whether it would work or be an expensive failure.
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Old Apr 07, 2012, 01:32 PM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
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I wanted to avoid the semi-technical explanation... Might as well lay it out here

The motor's Kv value tells you how fast it wants to turn per volt of input. In your case, this is 1200 RPM per volt. Increasing voltage, of course, will increase the RPMs the motor wants to spin at. Anytime you put a prop or other load on the motor, you're forcing it to spin slower than it wants to, which means it'll draw some amount of current. Generally, the motor will be drawing its maximum safe current when its RPMs are pushed down to about 75% of the no-load RPM.

Electric RC pilot's number one law: Current makes heat. Too much heat means stuff fries.

When the motor has a good prop for 3S operation (meaning it's being used at or close to its full potential with around 11.5-12V input), everything works well. However, increasing the voltage to the motor will make it try to spin faster, but it won't be able to get going as fast as it wants. The result is that it draws quite a bit more current (it's not a linear relationship) and the heat produced by the motor increases accordingly. The motor can't dissipate this extra heat quickly enough, so it gets too hot and smokes or de-magnetizes.

Using a smaller prop allows the motor to spin up to those higher RPMs, which keeps the current and heat down. Whether or not a smaller prop is a good option will depend on the plane itself, but not many planes will still fly comfortably if you just add a cell and then prop down like this.

That's the motor side. The ESC is a whole different can of worms, mostly because of the built-in BEC which I assume you're using to power your receiver and servos. Generally, the voltage ratings on an ESC are not to be messed with. If it's rated for the extra voltage (current is sort of irrelevant here) and the BEC can still supply enough current for your radio and servos work with, then you'd be fine with the 4S pack. However, the motor itself is still a limiting factor here.

The 4S pack would also be at least 33% heavier and substantially thicker, which could pose other non-electrical problems.
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Old Apr 07, 2012, 01:59 PM
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United States, MI, Davison
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Quote:
Originally Posted by C₄H₁₀ View Post
I wanted to avoid the semi-technical explanation... Might as well lay it out here

The motor's Kv value tells you how fast it wants to turn per volt of input. In your case, this is 1200 RPM per volt. Increasing voltage, of course, will increase the RPMs the motor wants to spin at. Anytime you put a prop or other load on the motor, you're forcing it to spin slower than it wants to, which means it'll draw some amount of current. Generally, the motor will be drawing its maximum safe current when its RPMs are pushed down to about 75% of the no-load RPM.

Electric RC pilot's number one law: Current makes heat. Too much heat means stuff fries.

When the motor has a good prop for 3S operation (meaning it's being used at or close to its full potential with around 11.5-12V input), everything works well. However, increasing the voltage to the motor will make it try to spin faster, but it won't be able to get going as fast as it wants. The result is that it draws quite a bit more current (it's not a linear relationship) and the heat produced by the motor increases accordingly. The motor can't dissipate this extra heat quickly enough, so it gets too hot and smokes or de-magnetizes.

Using a smaller prop allows the motor to spin up to those higher RPMs, which keeps the current and heat down. Whether or not a smaller prop is a good option will depend on the plane itself, but not many planes will still fly comfortably if you just add a cell and then prop down like this.

That's the motor side. The ESC is a whole different can of worms, mostly because of the built-in BEC which I assume you're using to power your receiver and servos. Generally, the voltage ratings on an ESC are not to be messed with. If it's rated for the extra voltage (current is sort of irrelevant here) and the BEC can still supply enough current for your radio and servos work with, then you'd be fine with the 4S pack. However, the motor itself is still a limiting factor here.

The 4S pack would also be at least 33% heavier and substantially thicker, which could pose other non-electrical problems.
Usually I don't understand "the semi-technical explanation" but you did a great job of explaining this, so thank you very much.
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Old Apr 07, 2012, 05:47 PM
Reduce the drama...
rick.benjamin's Avatar
USA, OR, Damascus
Joined Apr 2004
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In another thread, you posted photos of the pack.
It has 4 balance leads.
That makes it a mislabeled 3S pack
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Old Apr 07, 2012, 05:57 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
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Quote:
Originally Posted by rick.benjamin View Post
In another thread, you posted photos of the pack.
It has 4 balance leads.
That makes it a mislabeled 3S pack
Ahhh, the post about the Transmetic pack from Leaders Hobby. They sell 5C packs if you need one.

Good catch Rick
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Old Apr 07, 2012, 06:04 PM
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
12,252 Posts
I have a 3C 3S 2500mAh Zippy pack in my transmitter. Love that thing

I saw the mislabeled-pack post a few minutes ago... My advice would be to forget that thing altogether and go find some Sky Lipo or GensAce packs from HobbyPartz. They're good stuff and they come with the right labels
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Old Apr 08, 2012, 12:20 PM
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United States, MI, Davison
Joined Feb 2012
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Quote:
Originally Posted by rick.benjamin View Post
In another thread, you posted photos of the pack.
It has 4 balance leads.
That makes it a mislabeled 3S pack
Yeah, I thought maybe I should put this in the battery area of this forum. I checked it on my HobbyKing 200w charger and it is not only marked wrong but has a dead cell. Another peace of crap from Leaders Hobby!
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