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HomeAircraftHelicopterHelicopter Main Discussion › Question on mah draw per flight
03-18-2015 10:45 PM  3 years agoPost 1

rrKey Veteran


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I running a 600 nitro with 600mm blades

I have the following equipment:

3 - JR8917 on Cyclic running direct on the skookum 7.2v
1- JR8900G on tail running a stepdown @ 4.8 volts
1- futaba 3155 digital on throttle running thru the perfect reg at 5.3 volts.

1- Perfect regulator duo attached to the 7.2v lipo
1- Skookum SK540 flybarless controller - running at 7.2 volts

1- Multigov pro - running at 7.2 volts.

On a flight, approx. how many milliamps should I expect to see drawing on a new Lipo battery?

What can I put on board to capture this data??

JR - JRPF8917HV - DS8917HV HV Ultra Speed Cyclic Servo
•Type: Digital
•Application: 50-size and larger helis, cyclic
•Torque: 220 oz-in
•Voltage: 6-8.5V (2S Li-Po battery)
•Weight: 2.5 oz

JR - JRPS8900G - DS8900G Ultra Speed Digital Gyro Servo 4.8V

•Type: Digital
•Torque: 48 oz-in @ 4.8V
•Speed: .05 sec/60 deg @ 4.8V
•Voltage: 4.8V only
•Weight: 2.1 oz

Futaba: S3155
Type Digitial
4.8V 28 oz-in (2.0 kg-cm) 0.16 sec/60°
6.0V n/a n/a
Weight 0.72 oz (20 g)

Skookum SK540
4.8v - 10volts

03-18-2015 10:55 PM  3 years agoPost 2



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I'm going to go with about 400 mah per flight.

That said, that is a question that is darned near impossible to accurately predict, so I'm glad you are asking how to measure it. Thing is, the flight style will be a bigger determinant of MAH-out than the gear on board. The gear on board is only a determinant of potential, not actual.

So, to go about measuring:

This should be relatively simple with a Lipo, since they tend to show about the same amount of Mah OUT as Mah IN when charged. So going in with the 400 MAH estimate, Fly a couple times and see what goes back in MAH-wise on your charger.

Keep in mind the first point I made, that flight style is the biggest determninant. If you go about measuring on a hover flight, then use that as your planning factor to fly multiple flights doing hard 3D, you are going to be unpleasantly surprised. If you fly hard, measure Mah-out on a hard flight. If you fly easy, make sure you reexamine the Mah-out as you progress and start flying harder. Of course, you should always use a volt checker anyway.

03-18-2015 11:24 PM  3 years agoPost 3


42½ N, 83½ W

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I put this data together a few years back,

03-19-2015 12:36 AM  3 years agoPost 4

rrElite Veteran

Ottawa, Ontario

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do 1 flight with a fully charged battery and fly it as hard as you can. then recharge after the flight this should give you a pretty good idea of what you are using per flight

03-19-2015 01:28 AM  3 years agoPost 5



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All good advice.
I'll add that my RX pack went down by about 285mA to 350mA per flight on my nitros.
That was the 600s and 700s.

My typical flights were about 8-9 minutes.

Just charge it and fly it.
Charge and note the returned juice.

I literally never use the word literally right.

03-19-2015 01:30 AM  3 years agoPost 6



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I eventually installed a Jewel Generator by the way and started using about 1mA per flight and sometimes even landed with a RX pack that was more charged at landing than it was at take off

Just sayin

I literally never use the word literally right.

03-19-2015 01:01 PM  3 years agoPost 7

rrElite Veteran


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a basic digital display battery alarm will tell you what has been used and when to stop. Ive used one many times lately. Connects to the balance plug.

03-20-2015 04:56 AM  3 years agoPost 8



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I have the following equipment:
As a first estimate, you would have to determine a power budget.

For each component that draws power....

For sure, your servos will draw the most an FBL controller will only draw ~300mA max at any voltage....

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03-20-2015 05:28 AM  3 years agoPost 9


Penticton , B.C. CANADA

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What are you wanting to do with the info ?

I do a similar thing with my large logo's.
There all running jr 8917/256hv tail servo's off a 2s2p 4000 mah lipo rx pack.

I log all my flights so I can keep track of battery cycles and mah in/out.

I take a wider look at the rx consumption. My logo 700 or 800 uses about 300mah per flight on 3d.

So after 4-8 flights I'll recharge the pack and see how close to 300 I am.

My theory is if I see a spike in the consumption , something is up. In theory i'll find this out before I crash it.

The 8917 are proven and will follow kyle's recommended 1200 flight replacement program. (failures at 1800 btw)

The wider picture will give some peace of mind (potentially) without layers of electronics on board ( potential failure points )


What goes up will come down.... one way or another !

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