Okay. Next question. The heli flies fine for about 10 minutes, and then the motor starts sputtering. Shut down for a few seconds and it's fine for about 30 seconds.

I'm running a Thunder Power 11.1V 2100mAH battery, with a 3200KV motor (13T gear), with a 25 amp Align ESC. I have the ESC diectly under the cooling fan/ main gear, and it's still getting incredibly hot. Is this ESC too small to handle the load? My guy at the LHS said these ESC's that they send out with the Package deals tend to burn up really quick. Do I need to go up to a 35 amp?

Thanks Guys.

whtmex (Chad)

I would....


but 10 minutes is a good flight time.....
what voltage are your packs at when you finish flying.....

The charger is showing it at about 9.5V when it starts getting weird.

I am running the Castle Creations Phoenix 35 ESC with a 11.1, 2100 mah battery pack with no heating problems.

If I say 9.5v at the beginning of a charge....

I would cringe!!


I would bet that you are going waaay under 9v under load and that is a bad thing.....

10 minutes is a long time on a Trex. I'm guessing the "sputtering" you are talking about is the LVC of the ESC


when I had my Trex setup for 3D (3000 rpm headspeed)
I would stop flying after about 5 minutes.

when set at around 2400rpm, I quit flying at about 8 minutes

What is your throttle curve set at? If you are running a throttle curve at anything less than 80% for extended period of time the ESC will heat up. Most ESCs and motors run more efficient and cooler when the throttle of the ESC is run at 80% or higher.

Your ESC is telling you it is time to stop flying.
If any single cell in your pack goes below 3 volts you stand a chance of ruining your pack.
My Pheonix esc reduces power at a preset amount (not sure what at the moment) but when I hookup my balance charger I am seeing about 3.5 volts per cell.(full charge on my balancer is 4.2 volts per cell)
This is with 1320 mah packs and near 10 minutes flight time (mostly hovering)

Thanks Guys. Like I said, I'm new to this. I'm used to getting 15-20 min on my CP. Guess I'll need to get another pack so I can get some more flight time.

You need to hook up with someone who has a power meter so that you can analyze and fine tune your setup. The T-Rex pushes the limits of the CC25. Basic hovering and simple forward flight should be fine provided it's setup properly.

I think a 13T pinion on that motor with a 25A ESC is probably pushing it a bit. I bet that ESC would run much cooler with an 11T, but of course, your headspeed will be lower...

Still, 10mins is a pretty good flight time. It sounds like you're flying until the battery is depleted to the point that the ESC starts reducing power. That's way too far! You never want to discharge your LIPO more than about 80% if you want to get the maximun lifespan out of it...

In my previous post I mentioned I am using a Castle Creations Phoenix 35 ESC. I use the 11 tooth pinion and a Align 11.1 2100mah battery. I use a li-po battery alarm available at http://www.heliproz.com/prodinfo.asp?number=335444 and have that set at 9.0 volts. I have the ESC set at high governer and I am getting 8 1/2 - 9 minutes flight time sport flying. I have my radio throttle set at 85% on a JR 7202. I usually get 3.1 volts per cell on the charger.

I have the same thunder Power 15c 2100 lipo and I get 10-12 minutes hovering time on my rex - with 13tooth pinion - so you are getting correct times.

I have my voltage cut-out set to "high" as there is not really much between the settings and getting maybe most 1-2 extra minutes is just not worth damaging your expensive batteries!

A VERY IMPORTANT THING to know for newbies that I found out! The ESC low voltage cut-out protection is actually a percentage cut-out of your original batteries initial voltage.
Like I say - I have mine set on high - but what YOU SHOULD KNOW is NEVER disconnect your battery half flight and re-connect it! if you do this - DO NOT rely on your ESC low voltage cutout to save your battery... you need to mentally keep a track of how long you have been flying.

This is because, when you re-connect the battery, the ESC works out the low-voltage cutout based on the start-up voltage of the battery - and because the battery has now been used - that cutout voltage may - and probably will - be too low for your battery and might result in damage to your battery.

So if you have to disconnect and reconnect your battery half way through a charge - end your flight a little early or time your flights so you know when to stop!!!!

Note: I have a 25A ESC as well - the guy I bought my rex off had a neat idea - he csut some of the heat shrink away to expose the heatsink on the esc and mounted (with CA glue) a small computer fan to the esc with some small mounts.... works well and keeps the temp of the esc down makes a little noise but the heli is much louder than the fan anyway - lol

Be carefull setting it that low. If any single cell drops below 3 volts you could ruin your pack.

Your right, I have changed the setting to 9.6 volts........

Thanks for all the tips. The problem was the throttle curve. It was set linear. I set the curve to the manual's specs and got about 15 min out of it. No overheating, no ESC resets, battery is reading about 10.1V at shutdown. So I guess that solved that problem. This digital controller is confusing the heck out of me, but I'm slowly learning it. Tomorrow's task is figuring out how to set the different modes so I can switch between general and light acro flight. Wish me luck.

As far as the setup, don't really know much about the Rex yet. I just set it up according to the manual which suggested the 13T gear with the 3200kv motor and 25amp ESC. Like I said, seems to be working great now. Just finalizing the last few control tweaks so I can start actually flying.

Thanks Guys.

Whtmex (Chad)