As I stated in a previous post this is my first electric. Today on my second flight after about 5 minutes all power just stopped. Plenty of battery left. My first flight was very light on the throttle. This one was a little more aggressive. I have 5 A123 cells in an eflite power 46 turning a 13x8 APC electric prop. Castle creations phx 60 amp speed control. Static test showed 39 amps and about 600 watts. Low voltage is set correctly thanks to your previous help.

So what happened?

Did I exceed some limits on the motor or speed control? Does the motor draw significantly more amps when inflight and therefore shut something down. I tried the motor and speed control about two hours later and it appeared to run OK on the ground.

Where do I go from here? Help!!

Where do you have the LVC set?

Five minutes with an Eflite 46 on a 13x8APC with judicious throttle control is roughly where I'd expect the battery to be at the LVC point.

Why do you say "Plenty of battery left"? What does that mean?
Assuming a 5S1P set up you were more than likely out of 'juice'. As a matter of fact I'm surprised you got that far, I would have expected no more than 3 minutes with the set up shown here (lots of open ends).

My battery is 4600Mah. The extrema charger showed that the battery only needed 2,900 Mah to bring it back up to a full balanced charge

But where is your LVC set???

2.1 volts per cell

You say that your charger is an Extrema.
What little I've read about that charger indicates that it has no A123 mode.
Are you charging as if they were LiPo's? Or does your version have an A123 specific set up?
I have been using A123s for well over two years (Over one year as motive power) but have always used an A123 specific charger.
The FMA 4S first and for the last year the FMA 10S.
Each has a specific mode for these cells.

Or, have you found your problem in the meantime.

It charges A123 cells. You just set the max volts to 3.6 volts. I Think it is solved but I am not sure. I think it was overheating. I have put a large opening in the cowl in line with the firewall openings. I have since done a ground run and a test flight today. It did not shut down. Castle just told me that a momentary loss of signal will shut down the ESC and by returning the throttle to zero and then throttlling up power will be restored. I did not know this. I also know that every once ahwile I get a small throttle rev up when the main power is connected. I have a 72mhz system. Signal loss or overheating not really sure. I had one very knowledgable guy tell me he has never had a Castle overheat and shut down. Cheaper ones yes but not a properly sized Castle.

Here's what E-flite says:

Option 2:
Motor: Power 46
ESC: Castle Creations Phoenix 60 (Standard settings with 12V Soft Li-Po cutoff and no brake)
Prop: APC 13x8E
Battery: Thunder Power PRO LITE 4200mAh 4S2P (THP42002S2PPL x2 in series)
Flying Weight w/Battery: 5.4 lb

Amps Volts Watts Input Watts/Pound RPM
47.4 14.1 670 124 8220

Expect strong performance with very short takeoff rolls and a great balance of thrust and top speed. Average duration is approximately 8 to 15 minutes depending on throttle management.

I usually get about 5-8 minutes on my 4S setup with this motor depending on how I fly. Maybe the motor overheated? Do you have enough cooling around the motor and ESC?

Well I have had 4 flights on this power system using the 13x8 prop with No problem at all. Noting is even close to being hot. I guess I will conclude it was a glitch that caused the shutdown. I am using a 72 MZ system.