Anyone ever get the itch to grab the battery before fully charged in order to beat the sun going down?

Do it all the time. Usually won't start with less than 60% and no plans on flying far...just playing around.

Not a good idea for me because more times than not I fly over water.

Wow. I get the itch but I haven't done it only because the "fly aways" stories I've read, usually the phantom started with low battery. (Made my statistics up on the spot but you get the point).

It would seem harmless if I just want to fly no further than 900 ft or so

G_MEZ_G Posted at 2016-5-1 12:41
It would seem harmless if I just want to fly no further than 900 ft or so

Not at all.
It won't make your Phantom fly away (how could it?) but it there are more than enough accounts of Phantoms failing in flight after launching with part charged batteries.
Perhaps there's a reason that DJI specifically advise against it in the manual?

Maybe the app does not calculate % right if it's not starting at full? So perhaps the software is wrong and you MAY actually run out of juice?
Would be nice to hear some specifics from DJI.

gtokarsk Posted at 2016-5-1 13:13
Maybe the app does not calculate % right if it's not starting at full? So perhaps the software is wr ...

"Would be nice to hear some specifics from DJI."

They are quite specific in the manual - Don't do it.

No difference than having a full battery, flying a bit, landing at 3/4 battery and taking off again.

The ONLY reason to "not do it" is because people will fly too high or too far...more than the battery has to return safely. Beyond peoples stupidity (I can easily be included at times) there is no reason to start off with a 100% battery, each and every time.

FAS1 Posted at 2016-4-30 22:38
No difference than having a full battery, flying a bit, landing at 3/4 battery and taking off again. ...

I am leaning to agree with you, hence my hope DJI will chime in and "explain".. Manual is all for one, and one for all.. Not saying I will not follow the manual, but I do like to know if there's any specific reason that we all should really be aware of....
And yes, we can all be the "idiots" from time to time, sometimes it's called an "airshow syndrome" or sometimes it's just "being human"... ;)

gtokarsk Posted at 2016-5-1 15:00
I am leaning to agree with you, hence my hope DJI will chime in and "explain".. Manual is all for  ...

It might be fine to fly a bit, land and fly again soon after.
You aren't aware of the issues that people have had flying with batteries that had been stored and partially discharged only to fall from the sky.
There have been enough incidents to make you take DJI's advice.
But do whatever you like - it's not my Phantom at risk.

Well, i feel it hard to believe the all the safeguards showing you battery % will not work right, and yes, I have not heard of all the accounts... seems like you have.. so you think people had incidents of the drone just cutting, and it seems that it may have been battery related? That is weird! Then again, I do know that when say you got 60% and the amps kick in, that 50 can become 30 very fast...  Also, the initial warning of not flying below 30% on first 6 flights of a new battery, all that does make me feel a bit suspicious...  I assume you have not seen any explanation from DJI on any forum, that actually made some sense?
For now I do not fly on not full batteries from the start, but sometimes continue flying after a short landing and changing take off point, so a short walk....  Maybe there's something if your battery has a long time to fully cool down and so on?  Puzzling, but better safe then sorry.. $1k falling out of the sky is not cool, for a multitude of reasons!

I took my battery that had 75% up to 400' and 4,500' out and returned to home.  Still had just under 50% when he came back overhead.

gtokarsk Posted at 2016-5-1 01:22
Well, i feel it hard to believe the all the safeguards showing you battery % will not work right, an ...

I missed the accounts as well. I fly mine when they are low just to discharge them. I don't go far or real high. I do a lot of touch and go runs to run them down. If memory serves the Phantom won't restart when the battery is around 6-7%.

I think it's all about risk, if you have just fully charged the battery (Or at least that is what the equipment tells you), then the likelihood of having power problems is reduced. Liability seems to be the name of the game nowadays.

At the end of the day whether it drops from 50 feet or 500 feet probably won't make much difference, so it's really up to each individuals judgement and experience to make the decision as they see fit.

For me (given my limited experience) it's have a spare battery (or maybe two) ready to go.

You need to be very careful with partially charged batteries, especially if they have been stored for a few days. A discrepancy may exist, whereby the voltage of a pack may drop dangerously low, whilst the Percentage indicator still shows sufficient capacity.

Please see my post that describes the issue: http://forum.dji.com/thread-41951-1-1.html

One problem with a partially charged battery is as follows:-

When you start the motors & take off, the voltages will drop.  You can check this for yourself by watching the cell voltage levels in the go app (you need the battery monitoring screen showing to see it).  Because a fully charged battery has plenty of power to spare, it doesn't cause an issue.  As the aircraft flies, the voltages will slowly come down, which we all know about.  As it passes say, 50%, the voltages are all well within safe limits so you can carry on flying.  What's not so obvious is that the battery has warmed up considerably since take off, which will itself, increase the voltages.  So, when you give it full throttle to ascend, there's still plenty of reserve power available to allow flight.

If you start out with a 50% battery level & the battery is cold, you won't have this buffer.  The voltages will be lower to start with.  Now, assuming it's a fairly windy day. the first warning you'll get (if your firmware's up to date) is "Warning, propulsion output limited to ensure the safety of the battery", which does as it says.  If you then find yourself fighting the wind, the aircraft may drift away, or you might get the next warning "Critically low power, the aircraft will land now, you can throttle up to reduce the speed of ascent, and move the sticks to avoid obstacles", even though the battery level meter might be showing 49%.  The aircraft will land where it is, give or take some adjustments by yourself.

I've experienced this myself, albeit under abnormal conditions & at very close range & low altitude when carrying extra weight.  But it does highlight what's potentially possible in high-load conditions.  I'd say, it's probably ok to fly on a partial battery charge if done carefully, but you do need to be aware of what to watch out for, rather than blindly assuming because you've got away with it once, you can do it every time.

Just remember, the percentage battery left is only a calculated level based on current conditions.  It's in no way an absolute.

Also, all of the above assumes your firmware has been updated to either 1.5 or 1.6, I can't remember which.  If the firmware is 1.4 or older, there's a good chance your aircraft will just shut off & drop like a stone.

Also keep to the following:
  
1. Charge packs fully before flying.. - Try not to use partially charged packs, especially if they have been left for a few days.

2. If you do use a partially charged pack, then hover for around a minute, and keep a Hawks Eye on each battery Voltage. - if any battery quickly drops to under 3.60v in around 1.5 minutes or less then stop flying and change the battery.

3. Do not use the Percentage as the only indicator to determine the state of the battery. - Turn On "Show the voltage on the main screen" and keep an eye on it. - if it goes yellow and stays yellow, then start to prepare to come back home or land somewhere safe.

nigelw Posted at 2016-5-1 19:35
One problem with a partially charged battery is as follows:-

When you start the motors & take off,  ...

Nigel. Totally Agree. You have put it far better then me.

I fly a lot with out 100%. Take off

Good discussion guys! Especially thx to dji-p3p1and nigelw - some really good logical explanation that can easily be understood, remembered and applied! Thx guys!
GT

nigelw Posted at 2016-5-1 06:35
One problem with a partially charged battery is as follows:-

When you start the motors & take off,  ...

I've experienced this myself, albeit under abnormal conditions & at very close range & low altitude when carrying extra weight.  But it does highlight what's potentially possible in high-load conditions.  I'd say, it's probably ok to fly on a partial battery charge if done carefully, but you do need to be aware of what to watch out for, rather than blindly assuming because you've got away with it once, you can do it every time.

Just remember, the percentage battery left is only a calculated level based on current conditions.  It's in no way an absolute.

Dead-on.  To attempt to help some of the non-electrical types who may not understand what can happen, here's a very short explanation of one scenario.

A battery is a collection of cells.  i.e. a standard D cell is not a battery.  It's a cell.  If you put two them together, you have a 2 cell battery.  If both are of equal quality, age, and charge, they should perform well as a battery.  But, if one of them is older, has an internal defect, or for some other reason is slightly lower quality than the other, you can get different results.  Voltage is a static thing.  It takes almost no current to drive a voltage detection device to indicate good voltage.  But, if you put a real load on the bad cell, that voltage will take a dive during the load, when the good cell holds up well under the same load.

Your battery has several cells.  If a couple of them aren't quite as good as the others, when you hit the throttle and those motors start drawing lots of current from the battery, those weaker cells are going to drop voltage further than the stronger ones.  Try watching your cell voltages while you fly and do certain things -- like full speed in one direction or another, climbing quickly, etc.  Notice how one cell might drop faster than another.  Now, if the battery is cold, it may drop so far that the firmware triggers a safety mode and forces a landing.

I read about these cold battery failures off and on all winter.  They seemed to be made worse by a couple of firmware updates.  I never pushed it far enough to have a problem until recently, when I went out cold on purpose to test it at about 65-70% after having sat for a week or so.  One cell dropped to red under load when I took off and flew aggressively a little.  Battery temperature was around 19C.  It wouldn't take much of that.  I immediately backed off and it slowly recovered.  I let it hover to warm up a few more degrees and then hit it again lightly.  No problem.  As it warmed up, I was able to keep flying more aggressively, giving it more and more load.  Again, if you're going to fly cold, WATCH YOUR BATT TEMP!

Why did the above happen?  All cells are not exactly equal.  Ideally, cells are matched when building batteries to make a better pack.  They aren't necessarily defective, just not quite 100% equal.  Cells can "wear/age" differently too.

Like any aircraft, watch your gauges and take care of your equipment!

FAS1 Posted at 2016-5-1 12:38
No difference than having a full battery, flying a bit, landing at 3/4 battery and taking off again. ...

"No difference than having a full battery, flying a bit, landing at 3/4 battery and taking off again. "

^ This!

Really, I understand all of the other precautions, but I think it's safe to say that if you're keeping an minds eye on your batteries before and after use, during storage, and especially looking at indicators after you've taken off with anything less than a full battery, your risks are low.

Not A Speck Of  Posted at 2016-5-2 06:49
"No difference than having a full battery, flying a bit, landing at 3/4 battery and taking off agai ...

'Really, I understand all of the other precautions, but I think it's safe to say that if you're keeping an minds eye on your batteries before and after use, during storage, and especially looking at indicators after you've taken off with anything less than a full battery, your risks are low.'

I am puzzled by the fact that the evidence is to the opposite and that a number of experienced flyers have all cautioned against flying on a partially charged battery. The warning message regarding limitation of propulsion was put there for good reason. Primarily it was because people were having the batteries crap out in low temperatures, but the same issue can occur because of other factors, notably high current consumption during full power manoeuvres.

There were cases where the aircraft would just shut off and drop out of the sky. This was always blamed on the 'battery shutting down', but this is a very unlikely cause. My personal theory is that during high drain movements, is that the voltage of the battery would drop below the point where the aircraft electronics package can function and the whole aircraft would shut down while the system reset. By the time it recovers, it is lying smashed on the ground. My reason for proposing this theory is because I have had the same thing occur in systems I have designed, so I know what it looks like.

Geebax Posted at 2016-5-2 09:07
'Really, I understand all of the other precautions, but I think it's safe to say that if you're ke ...

Agreed, Especially with the last paragraph..

Here is an extract from the spec sheet of a well Known ESC (SimonK Firmware) that I design in for my Racing Quads.

Low-voltage Protection: 4 Options: 2.8V/Cell, 3.0v/Cell, 3.2V/Cell, Off. The default is 3V/Cell. the system will automatically identify the battery with the lowest voltage and work according to the option set

I ALWAYS re-program each ESC on my racing quads to disable shutdown due to Low Voltage Protection as I would rather have a damaged battery Pack (Cost approx $40) rather then a crashed quad (cost $100 and above) In any case ive set-up telemetry to send low voltage alarms at 3.2V on any cell, however during the heat of a race at the final seconds dash to the finish line I sometimes have alarms blaring at max trrottle (have won many races this way). - bear in mind I have never yet lost/damaged a cell/bettery pack due to critically low voltages.

BUT the Phantom is very different machine compared to a light, agile and super fast racing quad flown low to the ground in very controlled conditions.

Im sure the Phantom ESC's would have Voltage protection built-in hence, in line with Geebax's final paragraph, the aircraft would at, some point, shut-off due to low voltage and fall from the sky.

Personally I would rather have any Low Voltage Shutdown in the Phantom completly disabled with Alarms Going Crazy as I would rather, under extreme (battery low) conditions, land the craft safely and replace a $190 damaged battery rather then have a craft in an uncontrolled crash and loose a >$1500 quad and risk addational damage to people or property. - saying all that I would strongly advise aganist carry on flying after the phantom battery hits 30% and land  as soon as safely possible.

FAS1 Posted at 2016-5-1 14:38
No difference than having a full battery, flying a bit, landing at 3/4 battery and taking off again. ...

What you are describing here is very different  to what others are referring to.  You are flying from a full battery in one session, and the aircraft's control system is aware of the batteries condition as it has been monitoring it from full.   The other scenario is when you pull out a half-charged battery out of storage that you used last week, and expect it to perform the same as a fresh battery that you have just flown and discharged from 100% to 50%.

Very good explanations. I just ordered another battery to cure the itch instead of taking the battery off the charger at half charged. I also bought a stock 100W charger for 35 bucks on Craigslist. Risk is not worth the reward, and the silver lining for me is that I have now been enjoying night flights more and more.

Regardless, the battery is still discharged. It doesn't matter if it was discharged thru use or sitting, a discharged battery is still a discharged battery, no matter how one wants to candy coat it.

I find it amusing that you are so convinced that the aircraft can tell, and react differently, to WHEN a battery was discharged and how and that it makes a difference to the bird.. No, what I am describing is the exact same phenomenon, a discharged battery, whether discharged from use or self discharging, is still a discharged battery, plain and simple.  

I haven't used my Battery in about 2 weeks, to  discharge it further to the critical flying message, I played with my Bird on the Simulator.( With Props Removed-. I will bring it back up to 100% on my next outing.

FAS1 Posted at 2016-5-2 22:25
Regardless, the battery is still discharged. It doesn't matter if it was discharged thru use or sitt ...

'No, what I am describing is the exact same phenomenon, a discharged battery, whether discharged from use or self discharging, is still a discharged battery, plain and simple.'

Not quite. The state of charge of the battery is a calculated value, not a measured value. And if the aircraft is relying on the calculated value to make decisions about whether it should continue flying or return to home, then it may not be getting correct information. There is some evidence that self-discharge is not managed in the battery's stored information, and can lead to an inaccurate assessment of the battery capacity.

FAS1 Posted at 2016-5-2 22:25
Regardless, the battery is still discharged. It doesn't matter if it was discharged thru use or sitt ...

No..Its not quite that simple.... - Yes! - a discharged battery, is a discharged battery. However its different from what angle you look at it...

Because....

There can be a HUGE difference between the True capacity a discharged battery is holding, and what the smart circuitry in the battery/aircraft "Thinks" its holding and reporting as a percentage.

This actually means that the aircraft may Think and Report a different percentage capacity from the True Chemical Charge State of the battery, because the reported state is a calculated value over time.

Let me explain with an example:

  

- When a battery is charged, the Smart circuitry in the battery keeps measuring the power (Current, Voltage over Time) going into the battery (mAh). Once the LiOn battery reaches its maximum allowable safe Voltage (normally 4.2V) the smart circuitry memorises the charge (as 100%) gone in and disconnects the charger. At this point your Phantom battery is fully charged and a normal battery reports 100%

- When a Battery is Used (put into the Quad and switched on) the Smart Circuitry starts to measure the Power being withdrawn from the battery.... This is where the calculation comes in... The smart circuitry calculates what’s Gone In minus what’s come out then applies a manufacturer’s efficiency formula/algorithm and reports the remaining battery Capacity in %

Now.. The Calcualtion and/or Manufacturers Efficiency formula, although quite accurate, does not always work the same for every cell in the pack as every cell is chemically slightly different. So as time goes on and the battery goes through a number of normal charge & discharge cycles the Calculated Value may differ from the True Chemical Charge a battery holds. – Also partial discharge/Charge cycles and Cold temperatures play havoc as they change the chemical chracteristics and deviate from the expected calculations and value at either end (Fully Discharged or Charged)

What’s even worse is that over time, on a stored battery, there is Safety Storage Discharge (after a set number of days), some internal self-discharge (not too bad in Lipos) or the smart circuit itself may draw out a very small amount, but over a longer storage period it all adds up, such that (And this is the IMPORTANT Bit) the Memorised/Calculated state of a battery may differ greatly from the Actual/True chemical state. Hence Your Battery Is Out Of Sync and is reporting a wrong capacity percentage. i.e. Go App may be reporting 60%, on a partially charged pack, whilst the true charge (Chemically) may be only 20% - hence when you fly and apply full throttle, there is a big drain, the voltage suddenly drops Critically low and your Phantom falls out of the sky.

So an inexperienced Pilot is let wondering why his craft ran out of power so quickly - Thats why we say - Try Not to fly on a partially charged pack/stored pack.

This is why we have to cycle packs – To Reset the Calculated Value that the Smart Circuitry in the battery is reporting and to bring it as close as possible to the Chemical Charge State of the battery. (Note: Not to extend the life expectancy of the pack) – This reset by the smart circuitry happens over a defined set of values. i.e. when the % capacity falls below 10% or the voltage falls under a certain value (I think 3.2V at rest). The smart circiutry then memorises that as the low capacity, as close as possible to the True Chemical state and as you then charge the pack fully, it memorises the maximum capacity as 100%..... Now its once agin in Sync...,  and then the calculation starts again as you use the pack... so on..and on...

Geebax Posted at 2016-5-2 20:57
'No, what I am describing is the exact same phenomenon, a discharged battery, whether discharged f ...

But you are gleaning over the point of my reply. A discharged battery is still a discharged battery, regardless of how it became discharged.

Now, the apps/internal whatever can certainly be reading the battery incorrectly, but that has nothing to do with the fact that the battery is still discharged. I don't dispute the measuring system(s) are not accurate, I am only arguing that flying on a partially charged battery is in no way harmful, as long as common sense is used and long distance record setting isn't on the agenda.

But using it in your back yard will prove no difference other than a shorter flight time. A discharged battery is still a discharged battery, regardless of the means used to measure said battery function, or the means in which it was discharged. The end result is all that ultimately matters.

Yes, it truly is that simple. No one cares about the capacity. They want to know if a battery that is rated at 75% charge needs to be 100% before flying. I say from about 150 flights experience that no, it does not.

FAS1 Posted at 2016-5-3 17:32
But you are gleaning over the point of my reply. A discharged battery is still a discharged batter ...

What you are saying is true but what everyone else here is getting at is -- it only ever seems to be aircraft with partially discharged batteries that inexplicably fall from the skies. You might safely fly with a partially charged battery and safely land it at 30%.  There are others that push their luck and go to 10% or less.  If the calculated value is say 20% off, you will be able to land without incident, blissfully unaware that your battery is only a few percent away from empty, and about to go into shutdown to protect itself.  Others may get down to a 20% reported reading, then the next thing they know their aircraft has shut down, fallen from the sky and they are scratching their head because they think they still had power in reserve.

What we've learned is that the value reported from a partially discharged and stored battery is unreliable.  It seems to be accurate if you start from full, and do multiple short stints in the same session (assuming reasonable delays between flights, otherwise other factors come into play like temperature of cells etc., as described above).

FAS1 Posted at 2016-5-2 05:25
Regardless, the battery is still discharged. It doesn't matter if it was discharged thru use or sitt ...

Maybe so,  but if you do a search on "Phantom fell out of the sky"  or similar,  you will find a common thread running through them all.  The user flew on a partially discharged battery that had been sitting for a while,  like a week or two.  Frequently the battery showed plenty of power available in the app,  like 70 or more percent.   Then they flew for just a couple of minutes.  The lucky ones noticed a low voltage condition that happened in seconds.  Most of them landed safely.  Most of the unlucky ones crashed.  Lots of people fly with a freshly charged battery then land briefly and take off again with the same battery with no problem.  It seems to be that leaving it to partially discharge on its own due to disuse somehow has an adverse effect on the battery firmware.  And drones fall out of the sky.  In any event,  since that issue became well known among most P3 users,  I have not seen nearly as many cases.  Maybe the P4 will not have the issue. All will be revealed in time.

Bottom line, dont do it. If you bird falls out of the sky you will be at fault and you will get blown off by DJI for negligence. You really only get to fly between 100 and 40% bat.

Why would you risk your phantom?
Less than full charge can make a variation in voltage and cause sudden shutdown of the battery.
We're not kids to not be able to hold our instincts.

FAS1 Posted at 2016-5-3 15:32
But you are gleaning over the point of my reply. A discharged battery is still a discharged batter ...

But using it in your back yard will prove no difference other than a shorter flight time. A discharged battery is still a discharged battery, regardless of the means used to measure said battery function, or the means in which it was discharged. The end result is all that ultimately matters.

It is not a shorter flight time that is the problem... It's the inconsistent/unreliable nature of a depleted/stored pack...

The issue with a Partially discharged pack, that has been stored for a while,  is that the state/extent of discharge is unknown. It is very normal for a depleted lipo pack that has been stored to be able to output full power for a few seconds and then Very Suddenly and without any warning Collapse.

I've had an almost depleted 4s High Performance pack that hit close to 120 amps for 3 seconds on a Yokogawa Power Analyzer and subsequently a few seconds later could not even fully light up a 12v car bulb.!

A pack that has been fully charged and then had a couple of flights in the same day off the same pack at different times is a different story as the reported charge state would be accurate enough.... However....

Flying on a pack that has been stored a few days partially discharged is asking for trouble. You may decide to hover in your back yard on it, but remember even a drop of 3-5 meters or a very  hard landing is very likely to damage the gimbal/camera...

One may choose to fly with a partially discharged/stored pack but may not not like the ultimate end result.

To the point above. Discharge on a lipo is Not a Leniar function. Look at how quickly a lipo pack dies after around 3.3 volts.
If you don't know accurately where your partially charged battery is on the curve, your quad could be dropping down to the ground very quickly (a matter of seconds) after takeoff