3 volt limit is to avoid permanent damage due to a single over discharge.
Going as low as 7% remaining will reduce the number of cycles the battery will last.

3.7 volts is a much safer resting voltage.

Rather than rely on voltage as an indicator of charge, do a non-balance recharge and see how much goes back in.
(Balancing can give higher values since the charger bleeds off charge to keep the cells in balance)

Hello all,

To move the CG back, I changed from 3300 mAh to 3000 mAh batteries.
Since charge percentages are not too reliable, I checked each cell voltage after flight: 3,6 V, whereas the left capacity shows 7%. Seems OK to me, since the voltage is well above the minimum 3 V.
Does somebody have experience with this approach?
Regards,
Wolfgang

Yes and for the same reason.  I had similar results.  I flew a set of 4 (I think they were Turnegy) 5s 3000's for a year and had not experienced any issues. Each one had about 30 cycles and showed no signs of failure including weakening near the end of the pattern.  They finished at around 15% and somewhere around 3.5 v.  I didn't check the voltage regularly after the flight only the %.  One cell was always lower by about 3-5% and I have no clue why.   I have had them go as low as 5% and still be over 3.0v

A lower "C" rating will also get you a lighter battery.  I have done quite well using 25 even though all of the "experts" recommend 30-40.

Ken

Just to chime in on battery life, 30 cycles is extremely low in battery cycle life. I'll go through 30 cycles almost in one race in my "other hobby"
Pretty much every manufacturer of Li-po batteries I've run uses a 20% rule of thumb for maximum battery life. If you drop below 20%, you'll shorten the batteries life. So, how often, and how accurate is that? No idea. But that's been my experience.
Thunder power batteries is right here in Las Vegas. We've been educated by them a few times with visits to our clubs, and their reps / sponsored pilots.

The point I was making was that I was at 30 each with that set of 4 running them down to 15%.   In cost per cycle that would be about the same as  60 on a ThunderPower.   The ThunderPower guys here get about 75 cycles before obesity sets in mostly because they are lighter.  They are swelling and going out at about the same rate as the Turnegys that I used.  They were just lighter and cost more!

However, your points are well taken.  20% is where it should be but, in my opinion that is to keep from getting the power drop off which I think starts around 10%.  I once ran a 4s 2200 I bought by mistake until the esc low voltage kicked in just so I would know how it felt as it lost power.   It ran down to the point I was taxing.  The ESC low voltage was set to 3.2 and I never reached it.  I think that means is that we/I may be setting the low voltage cutoff too low....or not.

Ken
 

A few years back I datalogged and found that my low voltage under full load (with 6s) at the end of a flight was about 3.55v/cell.  Another fellow sent me his datalogs on 4S with similar findings, 3.57v/cell.  We were running down to the approximate 21- 22% level when measured at the end of a flight after a few minutes recovery.  That will have a voltage in the 3.74V/cell range resting. When I got home and the batteries recovered/rested longer, both the % and voltage came up a bit, say 24% and 3.77ish.  I get about 100 cycles/battery on Zippy compacts.  I then use them for about 100 more cycles at low amp draw as a pack to run my charger at the field.

However, your points are well taken.  20% is where it should be but, in my opinion that is to keep from getting the power drop off which I think starts around 10%.  I once ran a 4s 2200 I bought by mistake until the esc low voltage kicked in just so I would know how it felt as it lost power.   It ran down to the point I was taxing.  The ESC low voltage was set to 3.2 and I never reached it.  I think that means is that we/I may be setting the low voltage cutoff too low....or not.

Ken
 

I actually don't use thunder power anymore either. I use Dinogy. Coincidentally, also in Las Vegas.

I think you're right about the percentage thing. 20% may be an extreme for being conservative and safe. I don't exactly follow it either, but for racing, I don't keep my batteries long. I don't think I've kept a set for a year. I buy 4 or 8 at a time, and maybe use them for 6 months. I give them away before I notice any performance issues. Or, they get damaged and I have to recycle them! Haha

More like it's there for the RC guys when they do the same thing.  Control line folks would never do that!

Ok Tim, I'll fess up.  I once put a battery in my plane after doing a short set up flight.  I had used about 1 minute 15 seconds, and then put it back in for a full pattern.  Yep, not very bright but it taught me to keep track of batteries and timer settings.  I hit the low battery setting and got to experience the taxiing that Ken mentioned.  It wasn't good for the battery.

I thought you also had made a TUT to give a "go or no go light" to avoid starting with a less than full battery; maybe I'm not the only one with low battery experience. At least this CL flyer has tested the low battery cutoff and I'm happy that it wasn't disabled.