Current needs?

[LRFitch]

Guys, How can I get a good estimate of servo power needed in a glider? In this case, the glider will have 17 servos, and eight of them will be driving the ailerons. The switches I'd like to use (Zepusu magnetic) are only rated for 15amps each. The glider will have two switches controlling power to two receivers. That appears to mean that about 8-9 servos will be powered by one switch. How do others determine what kind of current levels will be seen in their gliders before it is all wired up so true current levels can be measured? I'm not really looking for worst case estimates that could occur, but what is likely when all is "normal".

Larry Fitch

[AGriffith]

If you're drawing more than 15 amps you've got problems.

[LRFitch]

Mr. Griffith, After looking up "no load operating currents of about 250-300 mah for each servo, I tend to agree. Thanks for the sanity check.
Larry Fitch

[AGriffith]

In some real world numbers, I have a 60cc Corvus with 6 300 ounce Savox digital servos. The flight pack feeds a DLE 61 ignition and the receiver/servos and I burn about 320mah per 12 minute flight. This is with huge 3D surfaces and spanking on the plane.

[Scalesoaring]

With a sailplane as large as that (8.8m) and 5 or 6 servos per wing, I suggest you consider a power management system, such as a PowerBox, that will regulate the servo and receiver voltages regardless of battery type. In addition you gain over-current protection from any servo (retract for example), dual battery support, and they have magnetic switches as well. If you are set on just using a simple dual-battery system, at least use a good quality battery backer. And the Zepsus 15A switches are good for 30A surge currents, so they can handle a momentary overload.

For reference, my 9-servo 6.5m LS-4 has dual 2S 3800mAh LiPos through a PowerBox Evolution. I accidentally jammed the retract servo while it was on the bench, and all that fried was the servo. PowerBox paid for itself right there.

Bruce

[LRFitch]

Bruce, Thanks for the post and info. While I have thought about such a unit, not in the last several weeks. I will look into that approach.
Thanks for the wake-up,
Larry Fitch