Servo Current Draw ?
 

if my 2wd stampede weight about 5lbs 10oz and the front tire are 4.27inch of diameters and the both front wheel/tires weight 330grams how much approximately the steering servo can draw on the main battery if ( ex : if I run the car for about 40min ) ?

here the specs of the servo :


http://www3.towerhobbies.com/cgi-bin...&I=LXVEP2&P=ML

not alot on that servo... why do you ask?

Any servo with properly adjusted endpoints will not draw much at all. I experimented once with a multimeter and while "sawing" the wheel back and forth saw 200milliamp spikes on a similar servo properly adjusted. On a 9000T with endpoints that reached too far the spikes were closer to 1amp. Properly adjusted the spikes were under 300milliamps.

ok but I ask because I just want a estimation on how I can use mah on the main batteries with about 40min runtime.. do it value it to use a external 6v pack to power the servo does I would notice a increase in the runtime ?

The difference is going to be negliable. You'll have a hard time measuring any difference in run time just because variations in how much throttle you use on each pack will have more of an impact than the servo + rx draw.

To give you a better estimation, my 1100mah 6v rx pack I used on nitro cars would last at least an hour with two servos drawing on it. If you have a multimeter, just hook it up inline on the red or black wire of the servo (or the esc to see the rx+servo draw combined) and you'll see what it'll draw exactly. It's not much and I doubt it would make a difference of more than a minute or two.

in my old, nitro savage, i used to get a full 4+ hours out of my 1600mah rx pack. the servo will draw maybe 100-200mah at the most. it is only a 1/10 and the servos don't draw much current.

And if you using a switching BEC (either external or built into the ESC), the actual current drawn will be even less than the servo current.

im using the BEC built-in in the 1/10 mamba max esc

That's a linear BEC, so whatever current draw the servo draws comes directly from the battery.

A switching BEC is more of a "power transfer", so the higher the battery voltage is, the less current is drawn for a given servo draw. Ex: 5s battery and 1A servo @ 6v. 18.5v/((6v*1A) /80%) = 0.4A BEC current drawn from the battery. The 80% is a typical BEC efficiency figure.

Man, this is a bit of an eye opener. My heli servos can pull 2.2A each. Had to get a CC BEC Pro to handle the amp load (shut down in mid-air = epic fail). I suspect most properly adjusted car servos are under an amp.

Heli servos should also be able to be properly adjusted to correct the "amp load" Are Your servos constantly pulling amps if there not on an on/off channel,not sure .Plus you are probrably fighting alot of force from the main blade/ pending the size of your heli? I cant see shut down in mid air being less than very expensive.:neutral: