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Old Nov 15, 2005, 12:26 PM
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Drewmotion's Avatar
Mission Viejo, CA
Joined Jul 2001
413 Posts
Low voltage cutoff

I have a CC PH-10 hooked up to an AXI 2208-34 and a 3 cell TP 730 11.1v battery, spinning a 9x3.8 prop.

I seem to be hitting low volatage cutoff too early into a fresh charge.

The strange thing is that this is only a recent problem, I've had over 15 flights without event, but yesterday it happened about 3 minutes into the flight in a low hover, resulting in a crash!

The ESC is at the factory setting of 5v. Should I change it to a higher setting, or do you think I'm just over stressing the battery?

Drew
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Old Nov 15, 2005, 12:58 PM
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Bilbobaker's Avatar
United States, UT, Salina
Joined Apr 2003
3,117 Posts
You really need to check each cells voltage at this point.
Somthing is amiss there, and that is the sign that one cell is not equal to the others.
Set that esc to 3v cuttoff per cell or auto detect lipo if it's an option
Been there and ruined that cell.
BB

Quote:
Originally Posted by Drewmotion
I have a CC PH-10 hooked up to an AXI 2208-34 and a 3 cell TP 730 11.1v battery, spinning a 9x3.8 prop.

I seem to be hitting low volatage cutoff too early into a fresh charge.

The strange thing is that this is only a recent problem, I've had over 15 flights without event, but yesterday it happened about 3 minutes into the flight in a low hover, resulting in a crash!

The ESC is at the factory setting of 5v. Should I change it to a higher setting, or do you think I'm just over stressing the battery?

Drew
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Old Nov 15, 2005, 01:02 PM
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BigBreeze's Avatar
Joined Dec 2004
316 Posts
Hi Drew,

Pease YES, Increase LVC to 9.0 Volts at least...or select Auto-Lipo Cutoff if you have that option. When you reached LVC, that means the Lipos were at 5.0 Volts under load. They were most likely BELOW 3.0V/cell when resting(not under load), which is BAD!

**RULE OF THUMB : 3 cell Lipo = 9.0V LVC**

You may have already damaged your batts...just monitor their temperatures for a few cycles while charging. I'm sure others will chime in! The TP Lipo instruction sheet, or the ESC Phx Instruction manual, or the Battery beginner guide here on RCGroups has great info on how to properly set up for using Lipos.

Good Luck,

Marc
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Last edited by BigBreeze; Nov 15, 2005 at 01:14 PM.
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Old Nov 15, 2005, 01:16 PM
Glow Free Since Aug, 2005
tommy321's Avatar
Ottawa, Ontario, Canada
Joined Aug 2004
1,258 Posts
What’s been said above is correct. Set your LVC to 9 volts for a 3S lipo, and if you hit the LVC three minutes into the flight, you’re definitely overstressing your battery. Or better yet, if you can borrow a Phx-Link, update the firmware and use “Auto-lipo”. When using auto-lipo, you just have to remember to count the beeps when you start up the ESC.

Another tip, if you do a lot of low flying, try using the soft-cutoff instead of a hard cut-off. With soft-cutoff, the motor won’t stop, but you will feel the reduction in power. I use soft cut-off in all my planes for the exact reason that they won’t fall out of the sky if I happen to be in a low hover/harrier when I reach the 9 volt cut-off.

Tom
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Old Nov 15, 2005, 03:47 PM
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Drewmotion's Avatar
Mission Viejo, CA
Joined Jul 2001
413 Posts
Thanks guys,

I've been using two cell batteries for so long I actually didn't even think about changing it on the ESC until this happened.

The battery doesn't get warm during charging, but I'll be sure to monitor it.

Thanks for the tip on the soft cutoff. I saw that in the manual, but didn't know if it was safe to use.

I really do need to learn more about Lipo battery setup, I guess I've just been lucky up to this point There's just too much guess work on my part with the electronic setup, I really need to invest in a watt meter!

Thanks Again!

Drew
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