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Old Jan 07, 2010, 03:38 PM
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London, UK
Joined Aug 2005
1,295 Posts
Help!
No cut-off when using CellShield LVC and Castle Creations Griffin ESC

I am getting no LVC soft cut-off functionality on my CellShield setup.
My system is

TP 2100 3s 11.1v lipo
Cellshield set at 3.0; 3.3; 3.4; 3.5 etc via potentiometer
Castle Creations Griffin brushed ESC 40amps
[this is advertised with a "4.7v LVC" of it's own]
Astro geared brushed motor pulling around 20amps max and 10amps at 50% throttle

I have connected all wiring as per instructions.
I can see 3 green lights on the CellShield

I am also independently monitoring the voltage using an Astro Whattmeter

There is no LVC cut off noticeable even when the battery voltage drops to 9.5v (under load). I have tried various setting for LVC on the potentiometer.
The Cellshield was NIP.

What am I doing wrong? Is there something I need to de-activate the internal 4.7v LVC on the Griffin ESC in order for the CellShield functionality to kick-in?

Thanks for your help

Arun
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Last edited by arukum17; Jan 07, 2010 at 03:55 PM.
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Old Jan 07, 2010, 06:15 PM
Dimension Engineering
Akron, Ohio
Joined Jan 2002
1,705 Posts
How long is the battery dipping to 9.5v? It takes a few seconds for the CellShield to kick in (we don't want it cutting off on throttle transients, just true battery depletion)

Also it resets if you throttle completely back. Do either of these help? The internal 4.7V cutoff won't hurt anything.
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Old Jan 08, 2010, 06:30 AM
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London, UK
Joined Aug 2005
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When I set the LVC at 3.5v per cell (the max level) or 10.5v for a 3s lipo, the wattmeter was showing a dip under 10v for quite a while, altleast 20 sec, but there was no noticeable change in the power output/prop spin rate.

Yes, while testing I started from zero throttle (of course), work my way up to about 50% then 100% for 10 sec and then would often throttle down to 50% and even down to zero quite often, before letting it go back up again. I throttled to zero even when I was above 3.5v per cell. When you say this "resets" at zero throttle do you mean it "loses" all LVC functionality until the battery is unplugged if at any stage I zero the throttle? (I am a glider flyer so zeroing the throttle in the middle of a flight is not unusual)

Next time I will try the test with 3.5v per cell setting on the Cellshield and run it continuously at 75% throttle from a fully charged battery and let you know the results. What should a CellShield soft cut-off feel like... is it a gradual weakening of power in steps, or one sudden drop in power?

Thanks for your help... I was worried that the CellShield was simply not compatible with my (discontinued) brushed Griffin 40amp ESC.. but it appears that is not the issue.
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Old Jan 09, 2010, 03:18 PM
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London, UK
Joined Aug 2005
1,295 Posts
Repeated the test with freshly charged battery and without going to zero throttle in the middle of the test. Still no LVC functionality. Exact sequence of the test was as follows:

Charged TP 2100 11.1v lipo, to fully charged
Set CellShield at max clockwise position of 3.5v per cell
Switch TX on
plugged in lipo to motor
heard a double beep showing that motor was armed
saw three green LED on the CellShield
Increased throttle to 40% and then 50% for around 15 min
Volts decreased to under 10.5v - no response
Volts decreased to under 10.3v - no response
Volts decreased to under 10.0v - no response
I ran it under 10.0v for around 10-15 sec and then halted the test.

Will repeat with another battery to see it that makes a difference.
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Old Jan 09, 2010, 09:20 PM
Dimension Engineering
Akron, Ohio
Joined Jan 2002
1,705 Posts
It walks down in a series of steps. Every time you dip below the cutoff voltage (on the lowest cell) for more than one second, it re-scales the throttle output. There are 16 steps. So at any fixed throttle setting it'll feel like a gradual weakening.

The reset works as follows: if you throttle all the way back, it'll reset the step count to 0. If you're at the point where commanding full throttle is sending 33% to the ESC, you'll get maybe 30 more seconds of higher power (it'll start decreasing immediately again of course.) That's there for those "I need an extra ten feet to clear those trees and get back to the field" moments.
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Old Feb 14, 2010, 10:44 AM
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London, UK
Joined Aug 2005
1,295 Posts
I tested it again, this time with the in-line Wattmeter removed and the cut-off functionality is OK. Tried it with different batteries and in all cases when the voltage goes low the green lights flash and the motor gives a soft cut off (a series of steps as described by Comatose)... when I throttle back to zero it gives me one last burst of juice

however...


the cut-off appears to be "delayed" by a few volts... with the CellShield potentiometer set at 3.4v per cell, after the cut-off is reached and I unplug the battery and measure the resting voltage (battery is still warm) with my Astro wattmeter it shows be 9.1v (or 9.3v after I let it cool down for 15 minutes)... this is way below the safe level to avoid battery damage. I would have expected a resting voltage much higher...I would have expected load voltage to be 10.2v and resting to be a good bit higher.

I will retest after raising the setting on the potentiometer to 3.5v per cell and see what happens.

Any suggestions?
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Last edited by arukum17; Feb 14, 2010 at 10:50 AM.
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Old Feb 15, 2010, 08:43 PM
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London, UK
Joined Aug 2005
1,295 Posts
Retested setting the potentiometer to 3.5v per cell (the max level)
Now the spent lipo (after LVC shut down and detachment from the aircraft) shows 9.5v warm and just over 10.0v cold. Still just above the safe discharge limit.

Is this normal?
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