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Old Mar 07, 2012, 01:46 PM
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Italy, Sicily, Palermo
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Lipo question for my new plane twin air from robbe

The TWIN AIR is really beautifull......the cost in europe is around 250 euros....great price i just bought it from Germany.
The quality is excellent....
Only one problem i have to solve.....The request is to use a 4s 4500 25c lipo.....
I have Turnigy 5000 25c 4s .... i'm worried of using them .....If they are too high for the esc ( 2 ) and they burn.....and also about the weight.....?
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Old Mar 07, 2012, 03:58 PM
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Increasing the milliamp capacity of a battery will not cause anything to burn up.
The current pulled by the system is dependent on the motor and prop combination. Increasing the milliamp capacity of the battery will not cause additional current to flow. Increasing the voltage of the battery is a different situation. That could cause problems.

Now the increased weight could be a problem. How much weight are you talking about?

Glen
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Old Mar 07, 2012, 05:32 PM
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If you are going to use two of them you need to connect them in parallel so that you are doubling the mah but keeping the voltage the same.

The weight difference between a 3s 25c 4500 mah batt and a 3s 25c 5000 mah batt is not going to be very much if they are of the same brand and chemistry. Looking at HK site your talking anywhere from 30 to 80 grams.
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Old Mar 07, 2012, 05:38 PM
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Quote:
Originally Posted by ggcrandall1 View Post
Increasing the milliamp capacity of a battery will not cause anything to burn up.
The current pulled by the system is dependent on the motor and prop combination. Increasing the milliamp capacity of the battery will not cause additional current to flow. Increasing the voltage of the battery is a different situation. That could cause problems.

Now the increased weight could be a problem. How much weight are you talking about?

Glen
Hello well the difference in weigh between a 5000 and a 4500 will be 80 gr more.....But what about the c rate....if i use a 30 c instead also will cause me problems with my esc on standard motor prop equipmnet ?
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Old Mar 07, 2012, 05:43 PM
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Originally Posted by tacx View Post
If you are going to use two of them you need to connect them in parallel so that you are doubling the mah but keeping the voltage the same.

The weight difference between a 3s 25c 4500 mah batt and a 3s 25c 5000 mah batt is not going to be very much if they are of the same brand and chemistry. Looking at HK site your talking anywhere from 30 to 80 grams.
Hello, no i'm talking about using only one lipo ...4500 4s 25c or a 5000 4s 25c....
will burning my escs...?
if i put a 30c 4500 lipo the fact i use a 30 c will draw much more amps to the motor i suppose ...How does it work wich is the appropriate c rat to choose for a lipo ?
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Old Mar 07, 2012, 06:00 PM
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Originally Posted by FedericoA View Post
Hello well the difference in weigh between a 5000 and a 4500 will be 80 gr more.....But what about the c rate....if i use a 30 c instead also will cause me problems with my esc on standard motor prop equipmnet ?
Going to a 30C will not cause more current to be consumed.

4500mah @ 25C = 112.5 amps (The maximum current the battery could safely supply.)

4500mah @ 30C = 135 amps (Again the maximum current the battery could safely supply.)

Note: This is what the battery could supply safely.

However if the system pulls, for example 100 amps, with the 25C battery it will still pull 100 amps with the 30C battery.

Likewise if you replace the 4500mah battery with a 5000mah the system will still pull the example 100 amps.

Glen
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Old Mar 07, 2012, 06:18 PM
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Originally Posted by ggcrandall1 View Post
Going to a 30C will not cause more current to be consumed.

4500mah @ 25C = 112.5 amps (The maximum current the battery could safely supply.)

4500mah @ 30C = 135 amps (Again the maximum current the battery could safely supply.)

Note: This is what the battery could supply safely.

However if the system pulls, for example 100 amps, with the 25C battery it will still pull 100 amps with the 30C battery.

Likewise if you replace the 4500mah battery with a 5000mah the system will still pull the example 100 amps.

Glen
Well please help me on this.....I have a FMS T28 TROJAN 1400.....and i use a 4S 3300 30 C lipo.....well after the fifth flight the stock 55 amps esc burn out ...no damage at all at the plane safe landing.....

FMS says this plane can go normally with a 25c 2900 4s lipo...I have use a 3300 because was getting better balance and performance on 30c.....

30c where too much or 3300 mah where too much.....

I am confused .....
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Old Mar 07, 2012, 06:33 PM
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Originally Posted by FedericoA View Post
Well please help me on this.....I have a FMS T28 TROJAN 1400.....and i use a 4S 3300 30 C lipo.....well after the fifth flight the stock 55 amps esc burn out ...no damage at all at the plane safe landing.....

FMS says this plane can go normally with a 25c 2900 4s lipo...I have use a 3300 because was getting better balance and performance on 30c.....

30c where too much or 3300 mah where too much.....

I am confused .....
You need to get a wattmeter and determine exactly what the current drain is.

Are you using the stock prop?

Glen
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Old Mar 07, 2012, 06:34 PM
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Originally Posted by ggcrandall1 View Post
You need to get a wattmeter and determine exactly what the current drain is.

Are you using the stock prop?

Glen
Yes i do....
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Old Mar 07, 2012, 07:52 PM
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Well after you replace the ESC check the system with a watt meter.

Glen
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Old Mar 07, 2012, 09:49 PM
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Think of it as if it were a car.

Mah is like the gas tank. It can be a big one or a little one. The engine doesn't know the difference. It will run until the gas tank is empty.

C rating is like the fuel pump which supplies gas to the engine. The engine wants the fuel pump to supply enough gas so it can run at full power.

Motor amps is like the horse power of the engine.

When you push the accelerator peddle to the floor the engine will try to run up to full horse power, but only if the fuel pump can deliver enough fuel fast enough.

So, in your electric plane, when you throttle up to high, the ESC tells the motor to run at high, so the motor tries to do that. When it does, it puts an amp draw on the ESC and battery. It is the motor that is demanding the power, so it tries to draw that power from the battery.

So, if the batteries C rating (fuel pump) can't keep up with the amp draw (horse power) from the motor then the system fails.
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