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Old Feb 12, 2007, 06:06 PM
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Lenny970's Avatar
Greeley, Colorado, USA
Joined Feb 2000
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Quote:
Originally Posted by thunder1
Wow, you guys must be using some really good lipos. Or maybe just bad NiCDs. What is the voltage under load per cell for the NiCds/NiMHs you're using? .
The comparison is between very good lipos and the best Nimh cells available (nobody uses nicads anymore ) I don't have the actual voltage values, but others have made that measurement.

Lenny
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Old Feb 12, 2007, 08:45 PM
Registered User
College Park, MD
Joined Sep 2002
4,714 Posts
The cells won't last long if you're discharging them to 2.7v/cell. You should set the LVC to no less than 3 volts/cell.

FWIW, I try to never discharge to less than 3.5v/cell. That's full static load with a freshly charged cell.

Quote:
Originally Posted by kkens4
I just bench tested a 5s TP Extreme 2070.
I got 48 amps and 650 watts.
That's 2.7 volts per cell.
I'm not surprised.
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Last edited by thunder1; Feb 12, 2007 at 08:53 PM.
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Old Feb 13, 2007, 06:10 AM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
10,261 Posts
Quote:
Originally Posted by thunder1
The cells won't last long if you're discharging them to 2.7v/cell. You should set the LVC to no less than 3 volts/cell.

FWIW, I try to never discharge to less than 3.5v/cell. That's full static load with a freshly charged cell.
That's under load, not discharged.
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Old Feb 14, 2007, 12:08 AM
Registered User
College Park, MD
Joined Sep 2002
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Right. 3 volts/cell. Especially for the newer generation cells. The point being that if you're drawing them down to below 3 volts/cell you're drawing too much current from them.
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Old Feb 14, 2007, 12:38 AM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
10,261 Posts
Quote:
Originally Posted by thunder1
Right. 3 volts/cell. Especially for the newer generation cells. The point being that if you're drawing them down to below 3 volts/cell you're drawing too much current from them.
I don't think so.
Here's some more numbers from the power train I recently set up.
Mega 16/15/3
Jedi opt 90
APC 5x4.5 prop
TP Extreme 5s 2070
Bench tested on a wattmeter for 7 seconds.

960 watts-65 amps 1-2 sec. 2.95 volts per cell
900 watts- 62 amps 3-5 sec. 2.90 volts per cell
745 watts-55 amps. 5-7 sec. 2.7 volts per cell

The battery is still healthy, and has less than 35 cycles on it.
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Old Feb 14, 2007, 11:43 AM
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College Park, MD
Joined Sep 2002
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So you're not using any LVC at all? How hot do the cells get?

Here's a battery discharge graph of the TP 2070 cell at various discharge rates. Even at 25C rates, the voltage never drops below 3.3 volts until the pack is discharged. You'll notice the cutoff is 3 volts.
http://www.rcgroups.com/forums/attac...hmentid=951613
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Old Feb 15, 2007, 03:48 AM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
10,261 Posts
Quote:
Originally Posted by thunder1
So you're not using any LVC at all? How hot do the cells get?

Here's a battery discharge graph of the TP 2070 cell at various discharge rates. Even at 25C rates, the voltage never drops below 3.3 volts until the pack is discharged. You'll notice the cutoff is 3 volts.
http://www.rcgroups.com/forums/attac...hmentid=951613
Well, I don't know what's going on.
The cells are barely warm after a complete discharge.
The bursts don't heat it up at all.
Either my readings are off, the battery is underperforming, or the charts are off. Maybe it's something else entirely. I don't know.
The Jedi Opt 90 has an automatic lipo detection, and detected 5 cells.
At any rate, this is why I have an Eagle Tree Pro Data Logger ready to go.
In the near future, I'll be using the logger exclusively.

EDIT: Sorry to be off topic so long. It wasn't intentional. It's funny how threads can meander if you don't watch out.
I'm really looking forward to the CASA event.
I hope there's a good turnout and nice Spring weather.
I REALLY hope I can make it there.
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Last edited by kkens4; Feb 15, 2007 at 04:28 AM.
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Old Feb 17, 2007, 09:55 AM
D.G.B.
KOMET 44's Avatar
Southington, Connecticut, United States
Joined Jun 2000
2,951 Posts
So,This event will be open to begginer's &first time hotliner pilots?

KOMET44
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Old Feb 19, 2007, 08:50 AM
corrupted - 17x18 or more
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College Park, Maryland, United States
Joined Nov 2003
506 Posts
Quote:
Originally Posted by KOMET 44
So,This event will be open to begginer's &first time hotliner pilots?

KOMET44
Definitely. This is a chance to fly with, and learn from more experienced flyers. The experience you will gain by attending will make a quantum step in your flying and plane set-up capabilities.

Don
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Old Feb 24, 2007, 08:14 PM
D.G.B.
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Southington, Connecticut, United States
Joined Jun 2000
2,951 Posts
Thanxs ,Don.I guess I'll be there.Lets hope for good weather.

KOMET44
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Old Apr 27, 2007, 10:49 AM
BANNED!!!
soholingo's Avatar
Laurel, MD
Joined May 2001
12,686 Posts
Setup

I am posting just prior to going to set up for the contests tomorrow. A few folks are showing up early to practice and help set up the field. I have a new camera so I am hoping to be able to capture some real footage this year. Past years have been crapshots.

At anyrate I will update everyone later... if you are within driving distance please come out to the field. just send me an email to soholingo@gmail.com with your phone number and I will call you back.

The weather is a bit dreary, but the winds seem to be down and Saturday and Sunday are forcasted to be great flying days.

more later...
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