LiPo degradation and motor performance

I've been flying a copter with a mix of new and old batteries and I've seen this several times.  It looks like the copter loses partial power to one or more motors, almost immediately after takeoff.  I'm wondering if the batteries have been improperly stored or otherwise damaged.

I've read a bunch over the years about storing LiPos at 60-80% charge to extend battery life.  Has anyone had negative effects of storing them at full charge for long periods?  Lets say on the order of 1 month.  I have a bunch of second hand batteries that are ~3 years old, 3s1p 30C Zippy Flightmax 5000s, that won't allow me to fly a small quad almost immediately after a full charge to 12.6V.  I'm guessing they weren't taken care of properly and I don't want to repeat that with my new batteries.  

I have one battery too that I accidentally discharged to 8V a while ago which no longer provides enough discharge capability to fly as well, so I'm wondering if maybe that's what happened to the other ones.  The symptom looks the same.  Flies great with new batteries though.

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  • Hi all,

    1.  do not leave lipos on full charge for more than a week

    2.  get into the habit to put lipos on storage charge when u get back from flying and charge only when u have decided to go fly next day.

    3. keep a cut off cap for urself, 20 or 30 or 40 %, this ensures u dont damage a lone weak cell

    4. i keep 40% as it may take another 10%  to 15 % for safe recovery of multicoptor if u have to resort to "go home and land" as it does take an appreciable time to execute, 

    happy landings

  • one thing that comes to mind about this is that you should set the number of cells on your ESCs.  ESCs determine the cell count based on voltage and if your packs aren't fully charged (or don't charge up to the same voltage they once did) when your ESCs fire up it might think you have a different cell count then you really do causing things like ESC voltage cutoffs to occur prematurely.

    Not that is the case but the more I think about it the more I think it is a good idea to specify cell count, especially since more people stick with one cell count battery and thus propeller size.

  • Forrest thanks for the great ideas.  Joe, yep I use a voltage alarm and try to land around 11V.  I was using the battery that went to 8V to power something else (Gumstix module) and forgot the V alarm during the test.

  • You will permanently damage your LiPo batteries if you discharge them to a level below recommended.  Discharging to 8 volts is definitely too low. The quickest way to damage a battery is flying to too low a voltage.  ! time can do significant damage.

    If you are flying till the motors reduce in speed due to low voltage you are probably damaging your batteries.

    A rule of thumb is to discharge to about 20% of battery capacity.  When you charge your batteries you should look at how much of a charge is put back in.  Adjust your flight time to prevent over discharge.  I would suggest a battery low voltage alarm and indicator as well.


    Storing at full voltage will also damage the battery over time.  If you are not using for a month bring the charge to 50 - 60 percent.  It is a gradual deterioration when held at full charge for a period of time.  if you want your batteries to last as long as possible always store at 50 -60 and only charge before you want to fly.



  • MR60

    This won't help you as batteries can also just get tired from normal use as you know.  But the following is a good habit.

    I keep an Excel worksheet log of every flight.  Log the flight duration time and the milli-amps needed to fully recharge the battery.  Then divide the flight duration by that charge amount.  On average (how hard you fly will impact flight duration), you will see over time the minutes of flight per milli-amp of charge decline so you know when to replace the worn battery and what might have caused lower performance (didn't store it with a full charge, let the battery drain too far, etc.).  So also note each entry with anything unusual (high winds, long time between flights, let the battery drain until the copter dropped out of the sky, battery felt unusually warm after the flight or charge, etc.).

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