Battery Requirements for RC Plane
11-02-2003, 08:04 AM
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Battery Requirements for RC Plane
Soon, I will be getting an EP plane. I’m trying to determine which batteries should be used.
I see that batteries come in voltages like 7.2, 9.6 etc.
But servos are rated at 4.8V and 6V.
My receiver has a range of 3.5 to 26V and since it is driving the servos is it safe to assume that it will regulate the voltage to the servos? (I’m still waiting for the Rx to arrive so probably the manual will explain this but I would like to get a battery before it comes in the mail.)
My motor is a “Speed 540” other than that I don’t have any other specs. What are the typical voltage requirements of motors. I will be using an ESC so like the Rx/Servo combo I guess the ESC will regulate the voltage to the motor but I would just like to confirm with you guys.
Thanks!
-Kevin
I see that batteries come in voltages like 7.2, 9.6 etc.
But servos are rated at 4.8V and 6V.
My receiver has a range of 3.5 to 26V and since it is driving the servos is it safe to assume that it will regulate the voltage to the servos? (I’m still waiting for the Rx to arrive so probably the manual will explain this but I would like to get a battery before it comes in the mail.)
My motor is a “Speed 540” other than that I don’t have any other specs. What are the typical voltage requirements of motors. I will be using an ESC so like the Rx/Servo combo I guess the ESC will regulate the voltage to the motor but I would just like to confirm with you guys.
Thanks!
-Kevin
11-03-2003, 08:15 AM
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RE: Battery Requirements for RC Plane
Actually, the ESC is what regulates the voltage to the receiver and servos. Most airplane ESCs have a BEC, battery eliminator circuit, that taps power off the main battery to power the radio equipment. The power is fed in through the speed control's connection to the receiver on channel 3 (for most brands, channel 1 on JR).
Pay attention to the BEC ratings in the instructions that come with your ESC.
What battery you choose will depend on the plane. It's backwards, putting the cart before the horse, to choose a motor first, then a battery, then an airplane. You either end up with a bad setup, or you limit yourself to a few airplanes that you might not necessarily want to fly. Always pick the airplane first, then the battery, then the motor.
That said, a 540 motor is designed to run on 6 or 7 large NiCd or NiMH cells. You can run 8 cells if you use a gearbox. Beyond that, the efficiency goes down and the motor doesn't last very long. Direct drive, you would run a 7x4 prop on 7 cells, an 8x4 prop on 6 cells. To run the motor direct drive on 8 cells, the propeller would be too small to be effective. Geared, I would use a Master Airscrew 3:1 gearbox, and a Master Airscrew 12x8 folding prop.
Pay attention to the BEC ratings in the instructions that come with your ESC.
What battery you choose will depend on the plane. It's backwards, putting the cart before the horse, to choose a motor first, then a battery, then an airplane. You either end up with a bad setup, or you limit yourself to a few airplanes that you might not necessarily want to fly. Always pick the airplane first, then the battery, then the motor.
That said, a 540 motor is designed to run on 6 or 7 large NiCd or NiMH cells. You can run 8 cells if you use a gearbox. Beyond that, the efficiency goes down and the motor doesn't last very long. Direct drive, you would run a 7x4 prop on 7 cells, an 8x4 prop on 6 cells. To run the motor direct drive on 8 cells, the propeller would be too small to be effective. Geared, I would use a Master Airscrew 3:1 gearbox, and a Master Airscrew 12x8 folding prop.
11-04-2003, 07:58 AM
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RE: Battery Requirements for RC Plane
Just in case you weren't aware, the letters mean the same thing as they do with alkaline cells. A "AA" NiCd is the same size as the battery in your TV remote, the AA Alkaline.
The most common "large" cell in larger aircraft is the Sub C. It's a little smaller than a C alkaline, and it packs a huge whallop (capable of more than 40 Amps). I'd say that's the largest cell that's practical for R/C aircraft use. You can also get C and D size NiCds, but those are a bit heavy for their capacity.
The A cell is the next largest. Some A cells, like the Sanyo HR4/5FAUP (don't worry, the letters are meaningless, it's just a model name) pack a pretty good punch in their own right (up to 40 Amps or so). You've gotta be more careful choosing here, though. There are good A cells, and there are bad A cells.
The most common "large" cell in larger aircraft is the Sub C. It's a little smaller than a C alkaline, and it packs a huge whallop (capable of more than 40 Amps). I'd say that's the largest cell that's practical for R/C aircraft use. You can also get C and D size NiCds, but those are a bit heavy for their capacity.
The A cell is the next largest. Some A cells, like the Sanyo HR4/5FAUP (don't worry, the letters are meaningless, it's just a model name) pack a pretty good punch in their own right (up to 40 Amps or so). You've gotta be more careful choosing here, though. There are good A cells, and there are bad A cells.
