sopwith

I only recently started using Lipo batteries and am seeing problems during flight. My airplane controls go dead mid flight and I crash. This is true for several planes. The motor and control positions freeze at some state until there is a crash. I suspect the ESC shuts down, maybe due to over heating. These are generic ESC not necessarilly for Lipo batteries, and I only used Nicad and Nmh before without incident. Everything works fine after the crash, so it is a non destructive failure. Has anyone seen a failure where the power to the receiver goes out in flight, and everything is fine afterwards? I was using 8 cell Nmh batteries and changed to 3 cell Lipo. The motors are Hi Max HA2015-4100, the ESC are generic 30 amp. I would think there would be no problem except the cutout voltage. I changed propeler to reduce current and still have problems. I am using typically 6:1 gear reduction and 11x4.7 GWS propellers. What ESC would eliminate the problems?

Thanks

hugger-4641

My Feedback: (6)

What kind of planes are you having this problem with, what kind of battery, what kind of radio? Having this problem with more than one lipo or the same battery doing same thing in different planes? Is the voltage cut off set right?
I've had wire break inside the insulation/connector on a 3 cell lipo in my T-28. It acted similar to what you describe, when I went into a steep climb I lost power to rx, midway thru the dive I got control back, landed it and found the problem. I also had a Super Cub that acted similar using lipo and nicads. Turned out to be radio interference with the rx.

Eplane65

My Feedback: (16)

The problem is likely:

1. A battery with too low a discharge rate. Try to get one that is at least 20C

2. Too small a capacity battery.

3. A cheap battery from some Chinese sources don't have a high enough discharge rate. See #1.

4. Get a wattmeter and figure out how your system is operating.

mrbigg

My Feedback: (21)

Get a watt meter for sure. It will tell you what is going on with your system. Really a necessary item for electric flight.

Flypaper 2

Make sure the ESC is up to the job too. Some say only to use 3 servos on 3 cells or 11.1 volts. Found out the hard way. the servos will draw more amps than the ESC is rated for and overheats and shuts off to protect itself and you have no control whatsoever. As soon as it cools down in a few seconds, it turns back on again. One check is to rotate the right stick and wiggle the rudder back and forth and feel the ESC for heat. Mine got to hot to touch, then shut off. Worse in the air as the surfaces have a load on them. Read the bec amp rating when when you buy the ESC and get one with about 2 amps and able to handle 4 servos on 11.1 volts

Ion01

Flypaper 2 is on it. I had the exact same problem and got a watt meter bought more batteries thinking the batteries were the problem but it all came back to the ESC. If it was just the power from the battery droping to low then you should only loose power to the motor (unless you have it set for a soft shutdown on a programable ESC) but should not loose power to the servos unless the ESC is shutting down due to overheating. Get an ESC that is rated for LIPO's and your setup.

sopwith

I have looked into my problem a bit...what voltage should a 3 cell lipo ESC shut off the motor? Mine was still running the motor when the voltage dropped below 8 volts.

Thanks

hugger-4641

My Feedback: (6)

A three cell lipo should cut off at no less than 9 volts! But as mentioned above, even 8 volts should still run the electronics after the motor cuts off.

sopwith

I have looked at universal brushless ESC and they mostly have an automatic cutoff that cuts out at 70% of the initial voltage. That is about 7.77 volts for a 3 cell 11.1 volt battery. Is this goint to damage the battery?

hugger-4641

My Feedback: (6)

That may or may not actually damage the battery, depending on the brand/quality of battery. But it is too low to allow most chargers to work. Most chargers give an error if any cell on the battery is below 3 volts (9volts total for a 3cell battery). So if your battery gets drained below 9 volts total, your charger may not want to charge it. I would recomend getting an esc designed for lipo's or get a programable esc.