The one thing that seems to be universally bad for Lipos is to leave them charged.
You should always put them to storage charge between uses.
I don't think the two weeks you mention (one time) is enough to cause a problem, but if you have been doing this often it will.

You can also set the esc's low battery cut-off setting to the higher limit and this will prevent the motor waiting for the timer to time out. Most esc's allow this. The only low cost one that I know that cannot do this is the Hobbywing Skywalker series. If it is indeed an internal resistance issue then a few sharp turns like a quick up and down elevator should help to shut the motor down. You should obviously not get the nose up too much! Some esc's also allow for a sharp cut-off, or a slow down process which is a better option.

Keith R

When you hit low volt of 3.2 and then run for a slow flight for the remainder of 5 minutes, what was the landing voltage and capacity?

Hi Fred -
Well, I suppose that the capacity when I landed was zero. But the capacity was zero when I took off because as I said, the packs reached the low-voltage cutoff immediately on start-up.
On one pack (pictured) pPre-launch, voltage was 20.6 ((4.12v/c) and 17.8v (3.56 v/c) after landing.
But note the immediate flat-line to 15.9v (3.2v/c) during the entire flight. All 3 Zippy packs do essentially the same thing.

Do you see any significance? The only thing I can think of is that once cell went bad in all 3 packs. I'll do some ground runs with a cell monitor so find out.

You not need discharge to storage voltage, enough if you do NOT charge after flight, that does not take any time :- )) Simply charge before you go fly.

I do not think problem is in batteries, if all of them did something wrong and other pilots do not have that problem, you probably do something wrong, it could be probably storing charged, that for sure kills battery, but I would also check if your charger works well (especially balancer), it must do 200 or even 300 flights.

BTW I did not find cycling helpfull at all. It can help if you fly at max C rate, but not if you fly under 10C whole flight, it is cycling all the life time :- P

I notice the motor's Kv is rather high (960Kv) for 5 cell set up.  As usually around 760-820 is the range for 5 cells, and any higher should be 4 cells.  But interestingly they recommend to use with 5 cells.

I'm no expert at this but, I've had some Zippy batteries I've used for 3 years and seem to be fine. I've lost two of them but that was to damage. I only charge them when I'm ready to fly and always (ALWAYS) discharge them to storage level after flying (unless I'm flying again the next day, then I charge them back up). I've only ever left they fully charged overnight.

Just my two cents.

Joe is correct, You should be running 4 cells with a k/v of 960 at those rpm.
At the moment your ESC is running at 60.1% which is way too low. Everything will run hot.
If you use 4s, it will run at 75% which is right in the ball-park.

My understanding from reading on here, the ESC has to switch more energy off internally and it builds heat, whereas when using lower voltage, the ESC does not work as hard.

( for the record, I am only reporting what I recall reading and my facts may be askew )

Joe is correct, You should be running 4 cells with a k/v of 960 at those rpm.
At the moment your ESC is running at 60.1% which is way too low. Everything will run hot.
If you use 4s, it will run at 75% which is right in the ball-park.

What Igor and Mark said.  I can't resist tossing in my two bits, because I design motor drivers that are similar to ESCs -- but it all really boils down to is a highly detailed way of saying "more voltage = more energy lost to heat".

The average current (and voltage) at the motor has to be the same -- otherwise it wouldn't generate the same average torque.  The ESC regulates voltage to the motor by chopping the battery voltage.  With a higher voltage battery, the pulses that the ESC sends have to be narrower.

With these larger-voltage, narrower pulses, the current in the ESC goes to a higher peak value and dips to a lower minimum value.  Because of the way that heat is generated in a resistance (I²R losses is the key phrase), this means that more heat is generated in the motor (and energy is consumed to do it).  Also -- and I haven't tested any motors for this so I don't have a good handle on it -- the higher applied voltage on the motor windings will cause more energy to be dissipated in the steel armature of the motor, both from eddy current losses and hysteresis losses.

Higher voltage on the ESC means that there's more switching loss in the ESC transistors.  Whether this is important depends on the detail design of the ESC, so if I wanted to know for sure if this was an issue I'd be measuring temperatures on a real one.  The same higher current peaks and lower troughs that happen in the motor happen in the ESC, which leads to conduction losses in the ESC (and the conduction losses are mostly the same kind of I²R losses as in the motor).

What I have not done, because it takes a lot of picky, detailed, time-consuming work, is to try to quantify how much of this happens in an electric power setup, and how much of it comes from each possible cause.  If I did do it, I'd just end up putting detailed numbers to what Igor is saying.

If batteries didn't fade toward the end of a flight, and if you didn't need some voltage overhead for power in the overhead maneuvers, then you'd want to set the thing up with as little excess voltage as you could -- but it's more important to have plenty of oomph in the clover and overhead 8 than it is to have the Most Efficient Setup.

What they said...................

Keith, buy the 4s 3700mah Zippys and you should have no problems. (Or if your plane is heavy use the 4s 4000mah.)
(My plane is 72oz and I get away with the 4s 3700mah 25c Zippys.)
You'll save some weight by using the correct battery. The ESC will run cooler along with the motor.
In fact you would get away with 25c instead of 35c. However the 35c batteries will be under less stress so will run cooler.
This is ok if the weight of them is ok for you.

OR use motor with lower KV OR prop with lower pitch, it will be far better :- )))


... but still, this is not answer why battery goes dead soon after start : -))