Guys, I did some static amp draw test and it's pulling 18amp. I currently have a CC Talon 35 but since it is pull less that 20 static I am looking to switch to a CC Talon 25 and save ~1/2oz. This lets me use a slightly heavier battery that would have better reserve left. Does this sound like it should work?

Best,    DennisT

Pulling 18A at full throttle? Or at governed speed? You should be checking at full throttle. At part throttle, motor current is higher than battery current and losses are greater at part throttle. You could try the 25 anyway to see what happens. It depends on how much cooling is available.

Stay with the 35 amp.  Once you start maneuvering the current will spike as the governor tries to hold the RPM.  A light prop and spinner helps reduce the spikes but 18 amps is too close the 25 amp rating for the smaller esc.

Bill,
The 18 amps measured are static not in-air. Would guess in-air is like 12.5amps.

Best,   DennisT

You are mostly right, but the current will spike as you maneuver to levels near or above the 18amps you measured.  It will depend on how the esc. Is programmed.

Bill,
The question is if the ESC is set for fixed rpm, governor mode (10K in my case) and the in-air amp draw around 13 amps and ground static is around 18 amps will the amps go up beyond 25 enough to damage the CC Talon 25 ESC. I can't see how the amps in a moving ship will exceed the static load. Has anyone tracked the in-air amps with maybe a CC Phoenix Edge data tracking ESC?

Best,   DennisT

Dennis -

It will not damage the ESC but you might have it shutdown in flight depending on the settings. With the Castles one way to avoid the ESC burning up in case of a prop strike is to set the current limiting shutoff to sensitive. This means that the ESC will only allow a small over current before shutting off to avoid damage. Now, in flight, if you pull tight into a wingover, the current spike might go beyond the limit and the ESC would shutoff.  May not burn up the ESC but if you crash you might lose both the plane and ESC.

What I think a lot people miss is that if the ESC is aggressively trying to maintain RPM (i.e. how you set-up the governor mode) the current spikes can be significant.  A way to alleviate this is to use a light prop; I no longer use APC props for that and other reasons.  Same can be said for the spinner.  The reason for the spike is that the motor has to overcome the airloads as well as the inertia of the prop, spinner and motor can while trying to maintain RPM.  When you do your ground testing, the motor is basically running in a steady state condition and the ESC is not having to compensate to changes the load at the prop (for example, when you pull into the vertical the plane will slow down due to gravity which will put a greater load on the prop which will also slow down as a result.  The ESC sees this and will add current to bring the RPM back to the desired number; this is what causes the fluctuations.  With the nose pointed down, the motor unloads and the ESC reduces the current).

Hope this helps.

Bill,
I agree with you on the current setting as I have had one ESC toasted due to a nose over in wet grass. The ship nosed in and the motor keep trying to turn the prop till it smoked, current was set a "normal". Since then I set it for sensitive an don't fly off wet grass. That being said I set my ESC for control line mode - fixed rpm (all three sections set to 10K, that I have checked with a tac). According to Innov8tions prop chart for a 10x6 on 14.8V the 2814 -980Kv should turn 11774rpm (full throttle) @ 26.82amps. Based on this there should be enough headroom to use the Talon 25 ESC and not trip out going vertical. However, you raised an interesting point that I have not considered. So before risking the ship, I think a call to Castle to see what the current spike would be to take the ESC off-line if set to "sensitive" would be worth the time. Will let all know once I talk to them tomorrow.

Best,  DennisT

Since Bill made a good point about spikes, I called Castle Creations and talked to their tech support. Bottom line is if the rpm is controlled to a fixed setting, then the static amps will be the max amps drawn, their ESC's are labeled for max continuous amps so my setup pulling 21 amps static should be just fine.

Now if you run a boost system you should check the amps at the boost rpm and size the ESC to not exceed that amp draw.

Best,    DennisT