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Using a 25C Battery on A 893KV motor

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Using a 25C Battery on A 893KV motor

Old 01-16-2010, 01:11 PM
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heavy metal thunder
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Default Using a 25C Battery on A 893KV motor

Recently, I purchased a 893 KV motor with a 80 amp ESC off of E-bay. After about 10 flights in a 100" wing span glider the motor gave out. I contacted the seller and he said that the 3 cell, 2250ma, 25c Rhino battery I was using too powerful. Spec for the motor is 893KV, 42A continuous, 50A Max, rated at 720 watts. I was using an 11 x 6 prop. I've been running smaller motors with this Rhino battery and have had no problems. I think the seller might be blowing smoke.
Old 01-16-2010, 08:04 PM
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Default RE: Using a 25C Battery on A 893KV motor

Definitely blowing smoke - get your money back.

Assuming the motor was rated for use with a 3S lipo, it doesnt matter how high the C rating is, as this is only the potential draw, not constant. If the motor doesnt ask for more, the battery wont give it more.
Old 01-18-2010, 01:00 AM
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Default RE: Using a 25C Battery on A 893KV motor

The battery didn't cause the motor to fail, but that's not the whole story.

Did you measure the current (Amps) you were drawing with that setup? Is it possible you were exceeding the motor specs? This would not be caused by the battery but by too large a prop.

- Jeff
Old 01-18-2010, 01:01 PM
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Default RE: Using a 25C Battery on A 893KV motor

Looking at the specs of the motor, the battery used, and using a 11x6 prop there should not be a problem, and it wasn't. The motor was rated to use up to a 13x6 prop. With a 11x6 prop the motor at max throttle it was pulling 435w. Max rating was 720w. Never had to use full power as a matter of fact 3/4 was enough to get the glider up to 400 ft in about 90 seconds. At first I was actually afraid the motor would damage my li-po by drawing too much current. The set up allowed me st least three launches to altitude with a few minutes of just flying around under low power. I was pissed off the seller would try and tell me it was the battery that caused the problem.
Old 01-18-2010, 01:20 PM
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Default RE: Using a 25C Battery on A 893KV motor

Yes, the seller is either not very knowledgeable or is blowing smoke. By his logic, a lightbulb should burn out because it is connected to a large power supply, the electric grid!

- Jeff
Old 01-18-2010, 01:51 PM
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Default RE: Using a 25C Battery on A 893KV motor

You're 100% correct jdetray. The seller is actually a E-bay retailer. I believe he just trying to cover his behind and blame me for his product failing. His reply of my battery causing the problem show his lack of knowledge and concern of his customers. I e-mailed them yesterday and informed them to reconsider their response.
Old 01-22-2010, 12:50 AM
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Default RE: Using a 25C Battery on A 893KV motor

How many Amps were you pulling? If you don't have a watt meter, get one. I run a similar set up on a glow conversion Spacewalker. I had quite a bit of trouble setting it up b/c when I'd throttle to full power, the motor would cut out. That almost cost me a plane. Fortunately I brought it down deadstick and was able to get close to the runway but the motor was toast. I was running two 3200mAh 20C 4s batts in series with an HV85 ESC and a similar Kv motor. I was drawing 65 amps when the throttle would cut out. Low and behold, if you multiply the mAh by the C rating and move the decimal over a few places you get 64. That's the amount of amps you can draw from those batteries. If you do the same to your setup, you're left with 56.25 amps. Well within the capabilities of your ESC and motor but turning an 11x6 prop? That's a big prop for a 2250mAh battery. I'd try a bigger battery, like a 3200mAh+. But check the amp draw. That's the most important thing.
Old 01-22-2010, 12:20 PM
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Default RE: Using a 25C Battery on A 893KV motor

Thanks for your response. I noticed that you were more concerned that I might fry my battery, which I was initially too. From a previous post, the motor was rated to use up to a 13x6 prop. With a 11x6 prop the motor at max throttle it was pulling 435w. Max rating was 720w. Never had to use full power as a matter of fact 3/4 was enough to get the glider up to 400 ft in about 90 seconds. A 2250 25c 3s is a little small, but I am only using it for about 90 seconds burst of power at a time and I was trying to keep the weight down. For the way I used them the Rhino 2250 25c batteries performed great with no problems at all, barely got warm, if at all. At first I was actually afraid the motor would damage my li-po by drawing too much current. The speed controller is rated at 80 amps so it was never a problem. I was pissed off the seller would try and tell me it was the battery that caused the problem. In your set up you were running two 3200 20c 4s batteries in series, that would give you over 28 volts to the motor. That motor must have been really going at full throttle. I ordered a Tunigy motor from Hobby City and using the same ESC, battery, and prop, that motor is running at 255w. I don't think I'll damage that motor.
Old 01-22-2010, 12:24 PM
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Default RE: Using a 25C Battery on A 893KV motor

Good, I hope things work out. Keep in mind though, just because the motor can turn a 13" prop doesn't mean the battery can handle the amp draw. Hopefully you're running a high quality ESC and then you can rest easy knowing it's protecting your batteries before damaging them. :-)
Old 01-22-2010, 01:02 PM
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heavy metal thunder
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Default RE: Using a 25C Battery on A 893KV motor

I know what you mean about specs can lie, that is why even though the motor could handle a 13" prop, I was only using a 11" prop, and your concern about frying batteries. I had a cheap 2200 15c 4s catch fire in one of my 2 meter soaring glider catch fire in flight. Fired the ESC and when the glider hit the ground the battery flew out and exploded on the grass, leaving a 1' burn spot. Mind you this was a simple glider with a 1050 KV motor, 8 x 4 prop, and 40 amp ESC. Boy I surprised when that happened. The glider was repaired and is still flying. Now days with the cost of Lipos dropping I buy only 25c or better rated batteries. I feel safer with the higher rated batteries in all of my soaring and speed applications.

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