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View Full Version : LVC setting for Electric Power 11.1v 3s Lipo?


zoomzoooie
10-25-2005, 09:42 PM
Hi all :)
I have a 12amp Coolrunning ESC and Electric Power 11.1v -3s Lipo powering a Komdodo H278, N50 outrunner with a 1047 slowfly prop. The ESC has "discharge level per cell" settings from 2.4v-3v per cell. The factory setting is 2.7v. What setting should I be using for my battery? Is the the same as LVC?


ZZ

Rugar
10-25-2005, 10:28 PM
Yes its the same as LVC. You need to set it to 3v per cell, which in your case would be 9v LVC for your 3s pack.

Greg Covey
10-25-2005, 10:57 PM
The discharge cell voltage level does not need to be set at 3.0v. The setting of 2.4v-3.0v per cell is based upon the model type and piloting skills. A lower voltage of 2.6v per cell allows for a longer flight when the motor is loading the pack. (e.g. 3D flying) Once the LVC shuts the motor off, the cell voltage rises above 3.0v.

Soon, you won't need to set this level as new products like the Skyvolt Discharge Protection Module (DPM) from FMA and the Cellpro DPM (coming soon) do this automatically for you based upon throttle setting.

Rugar
10-25-2005, 11:11 PM
The discharge cell voltage level does not need to be set at 3.0v. The setting of 2.4v-3.0v per cell is based upon the model type and piloting skills. A lower voltage of 2.6v per cell allows for a longer flight when the motor is loading the pack. (e.g. 3D flying) Once the LVC shuts the motor off, the cell voltage rises above 3.0v.

Soon, you won't need to set this level as new products like the Skyvolt Discharge Protection Module (DPM) from FMA and the Cellpro DPM (coming soon) do this automatically for you based upon throttle setting.

Maybe you dont, but most manufactures recommend 3v per cell for LVC. I try to keep mine at 3.8v or above resting voltage. Sometimes when flying something with low currant draw, even 3v LVC puts my resting voltage below 3.8v per cell.

Vamooska
10-26-2005, 02:59 AM
I gotta agree with Rugar too....3V is the safe norm.
Vammy

hoppy
10-26-2005, 04:49 AM
The difference in battery capacity between 3V and 2.8V is very small and little would be gained by running your packs below 3V but they could be damaged. Look at the slope of the graphs in this thread - http://www.rcgroups.com/forums/showpost.php?p=4317989&postcount=1

Extend the graphs below 3V down to 2.8V and check how many more mah good be drawn from the pack.

3V is my recommendation.

In fact, FMADirect, Kokam, recommends not letting the packs go below 3.3V per cell to prevent cell problems.
http://www.fmadirect.com/support_docs/item_1197.pdf page 14 See Zone of Temptation

zoomzoooie
10-26-2005, 05:26 AM
So if 3v is safer why would Coolrunning make the ESC start as low as 2.4v and only go as high as 3.v?

ZZ

hoppy
10-26-2005, 01:32 PM
"So if 3v is safer why would Coolrunning make the ESC start as low as 2.4v and only go as high as 3.v?"
You'll have to ask them.:)

Matter of fact, with some of the latest cells that hold their voltage very well, a cutoff of 3.3V/cell is recommended because the voltage drop at the end is very steep. Look at the ProLite2100 below. Once the voltage drops below 3.3V/cell, for all practical purposes, the pack is depleted.
http://www.wattflyer.com/forums/attachment.php?attachmentid=2368&d=1128824115

rcers
10-26-2005, 02:21 PM
3v is what 95% of us use. Happy for those who feel the extra 30 seconds is worth the cell abuse that you get for that 30 seconds of flying.

In fact I never fly to LVC on any airplane. I set a timer and fly to the end of that. I have several planes that fly over 20 minutes, some over 40 minutes. Just don't have it in me to do that!

Be nice to your cells. Forget about LVC and use the timer on your TX. Fly it for a lenght of time that is nice to your cells, motors and esc's. They need a break too! Most of my stuff is set for 8-12 minute flights. Enough for nearly anything.

Mike

Vamooska
10-26-2005, 04:38 PM
I don't know why some ESC manufacturers have the option of the lower LVC. BP's brand is the same way and I lost sales because of it. I like to keep in my mind the fact that lipolys while much more powerful are more volatile by nature. Keep respect for them up, and they serve well!
Peace
Happy Halloween
Jeff aka Vammy

Mark Wood
10-26-2005, 04:46 PM
I don't know why some ESC manufacturers have the option of the lower LVC.I understand the Europeans use 2.75v/cell as their LVC. Go figure. I'll use the accepted US guidelines of 3v/cell and not fly to LVC in the first place, thanks.

hoppy
10-26-2005, 08:28 PM
groundloop, mike and others, your right about quitting before the LVC kicks in....in fact, I can't remember the last time I had a LVC kick in. When the power starts to fade, it's landing time. It's not too hard to tell when the pack is hitting that curve at the end of the discharge. And in any case, I like where and when the landing occurs to be by my decision, not some gang of silicon wafers telling me what to do.:)

zoomzoooie
10-26-2005, 09:07 PM
I will use 3v LVC to be safe.

I got a reply from Coolrunning and they said use between 2.5v and 3.v...different pilots use different LVC's. Not exactly the anwer I was looking for. They also say a higher discharge battery should use 3v LCV.

I hear a lot of pilots flying for short a time, then flying again on the same charge. If you fly too many times you could reach the LVC. Timing the flights sounds like something I should be doing then. I have 3 batteries and plan to rotate them at the field. That should give me plenty of flying time and keep my batteries healthy.

Thanks for all you help to get me started on the right track

ZZ

Rugar
10-26-2005, 11:03 PM
Im interested in hearing Greg Covey's responce to this whole thread now.

hoppy
10-27-2005, 01:46 PM
Im interested in hearing Greg Covey's responce to this whole thread now.

Gregs recommendations are in line with some of the FMA product specs-

For instance, the FMA Super 20 ESC has these automatic cutoff settings.
2 lipo's - 5.3V (2.65V/cell)
3 lipo's - 8.4V (2.8V/cell)
4 lipo's - 11V (2.75V/cell)