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BEC Amperage Requirements

#1
I need an esc for my mighty mini sportster. Is a 2 amp BEC enough to power the Flite Test 5 gram servos or should I get something bigger?

I am looking at the G Force escs from Value Hobby. The 20 or 30 amp escs only have 2 amps, but if I go up to the 40 amp, it has 3.
 

Merv

Well-known member
#2
I have seen many reports that 9 gram servos draw about 3/4 amp each at full draw.
I’ve not seen any testing of 5 gram servos. That said, 5 servos on 2 amps sounds a bit risky.
 
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Piotrsko

Well-known member
#4
At full draw perhaps 3/4, but at stall much more. The rule of thumb was an amp per servo, receiver was free, but servo stall testing to see if it gets jittery or resets. Testing is holding the servo arm while moving the appropriate stick.

Just as reference: my 150 gram servos suck almost 2 amps, but at a whopping 150 lbin torque
 
#8
Given the mini sportster only weighs 260g including battery a 2A BEC should be sufficient.

But having said that, my default small ESC for models like this is the Castle Talon 15. 7g or less in weight with a 3A continuous / 8A peak BEC. An ESC will usually outlive several models, so it's not a bad investment for the future. Many of mine are 5+ years old and have survived helicopters, scratch built creations, flitetest foam models and indoor planes.
 
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Bricks

Well-known member
#9
From everything I have read a 9 gram analog servo draws 200 MA max draw could go up if the servos are stalling a lot ( servo throws not set properly or tight hinges ) which would send them to 250 MA that is 4 -9 gram analog servos per amp. So a 2 amp BEC can easily manage most of the FT planes with out issues. Most BEC `s rated for 2 AMP`s will have a max amps of 3 AMP`s. Now if you are using digital servos then a 3 amp is almost mandatory.
 

basslord1124

Well-known member
#10
Good thread, this makes me wonder if I'm overdoing it on my Shrubsmacker. I've got a 2A BEC and 5 servos. 3 of the servos are 5g and the other 2 servos are 3.7g.
 

Bricks

Well-known member
#11
Good thread, this makes me wonder if I'm overdoing it on my Shrubsmacker. I've got a 2A BEC and 5 servos. 3 of the servos are 5g and the other 2 servos are 3.7g.
I am sure you could do with less amps but why if you already have a 2 amp BEC. If weight is an issue then going to a smaller ESC with 1 amp BEC will work..
 

basslord1124

Well-known member
#12
I am sure you could do with less amps but why if you already have a 2 amp BEC. If weight is an issue then going to a smaller ESC with 1 amp BEC will work..
So you don't think I'd have problems with a 2A BEC and all those servos? I'm worried that I'm running too many servos for the 2A that it may brownout or something. Granted they are small servos, but I'm not sure on the amp draw.
 

Bricks

Well-known member
#13
So you don't think I'd have problems with a 2A BEC and all those servos? I'm worried that I'm running too many servos for the 2A that it may brownout or something. Granted they are small servos, but I'm not sure on the amp draw.
You should be good I have a balsa 48 inch low wing electric 3S running 6 9gram servos on a 2 AMP BEC ESC and have no issues receiver placement is the bigger concern.