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Old 02-12-2005, 03:49 PM   #1
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Default BEC voltage, servo speed, FET and digital servos

1. Virtually every under $100 ESC lists BEC voltage as 5 volts
while only the top of the line ESCs list 6 volts
most servos list 4.8v speed and torque and 6v specs are faster and higher torque. Does this mean that when I use a less expensive ESC with 5v BEC rating my servo will be slower and have less torque? Is their any remedy for this besides a more expensive ESC or the weight of a battery pack?


2. Digital servos draw more current. I guess some ESC and receivers have a FET output wire. Is this something that helps or will the digital servo still plug into the standard receiver?

Last edited by imjonah; 02-12-2005 at 07:11 PM.
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Old 02-13-2005, 10:45 AM   #2
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Default I am assuming the answer is ?

I am assuming the answer is ....Yes, you need to buy a 100+ pro-ESC if you want 6 volts sent to the servo so you can get its best speed and torque.
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Old 02-13-2005, 11:27 AM   #3
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Yes you want the esc with 6 volt bec. The novak GT7 and GTX both have 6 volt output. If you are running a cheap esc you will notice much better throttle control with a better esc also.
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Old 02-13-2005, 01:27 PM   #4
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A good esc will last a long time if taken care of. I spent $140 on a keyence 3+ years ago and it still works like the day I bought it. You could use a reciever pack to drop 6v into the servo but imo they are a pain in the butt.
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Old 02-13-2005, 02:56 PM   #5
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What the heck is a 'coreless' servo?

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Old 02-13-2005, 04:39 PM   #6
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Quote:
Originally posted by JayBee
What the heck is a 'coreless' servo?

-JB
Coreless is a certain type of electric motor. One of their advantages is more smooth... maybe other advantages, cant remember
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Old 02-13-2005, 04:43 PM   #7
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Default Re: BEC voltage, servo speed, FET and digital servos

Quote:
Originally posted by imjonah
2. Digital servos draw more current. I guess some ESC and receivers have a FET output wire. Is this something that helps or will the digital servo still plug into the standard receiver?
There's no relation between the current draw of a digital servo and the socalled FET wire.

Each and every digital servo draws more current, regardless of they have a FET wire.

Servos with a FET wire, do get 7,2 volt directly from the main battery. Thus they get a higher voltage (=more speed) AND there's no current limiter in the BEC in the ESC.

So if you already have a speedo, which you're happy for, the remedy could be to get a servo with a FET wire However, we're talking 100$-servos. But again, a fast servo is a grate, yet overlooked, hop-op, which will last for years and can be taken to the next car
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Last edited by Cole Trickle; 02-13-2005 at 05:29 PM.
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Old 02-13-2005, 04:46 PM   #8
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Default Re: BEC voltage, servo speed, FET and digital servos

Quote:
Originally posted by imjonah
1. Virtually every under $100 ESC lists BEC voltage as 5 volts
while only the top of the line ESCs list 6 volts
most servos list 4.8v speed and torque and 6v specs are faster and higher torque. Does this mean that when I use a less expensive ESC with 5v BEC rating my servo will be slower and have less torque? Is their any remedy for this besides a more expensive ESC or the weight of a battery pack?
That extra battery pack means quite a lot extra weight....

Check out this speedo - it's a Duratrax, but it's actually a rebadge Novak

Or check out the Novak Dually, nice speedo with 6 volt BEC and other nice stuff... Dont know the price though, but it might fit your budget...
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Old 02-13-2005, 05:14 PM   #9
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It's mainly an issue with BEC current, not voltage....

Most basic ESC's BEC only put out about 1A...

When the servo tries to draw more than 1A, the voltage drops...
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Old 02-13-2005, 05:26 PM   #10
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Quote:
Originally posted by Tres
It's mainly an issue with BEC current, not voltage....

Most basic ESC's BEC only put out about 1A...

When the servo tries to draw more than 1A, the voltage drops...
Hmmm. Dropping from 6 to 5 volt, means a speed loss of approx. 25%... At my opinion, that's quite a lot. But I highly agree about the current, that'll make it even worse
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Old 02-13-2005, 05:27 PM   #11
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If interested, here's an interesting document about digital servos here.
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Old 02-13-2005, 08:40 PM   #12
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FWIW all my "obsolete" Tekin escs have 6v 5a bec.Also, I read on Kinwald's thread on the Trinity site that he doesn't use digital servos-doesn't like them.
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