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LiPo Discharge, Is DJI Correct About This?
1100 31 2016-9-19
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JustGoThere
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Not trying to start anything, but as an RC person for years (Helicopters) you're told over and over not to discharge LiPos past 80% of the charge...

This roughly means 4 - 4.5 minutes for just about ANY RC senario (I'm sure the heli guys will back me up on this)
If you discharge to the end of a LiPo, you're going to damage it... this is taught over and over and over...
(don't fly at 3.7 volts (on a load) or less, or risk damage)

Once damaged, they appear to be fully charged, but will only last a fraction of the flight time before they simply stop.... and you fall...
(seen it happen to others several times over the years....)

How are the Lipo batteries for the Phantom any different?
I understand the electronics involved with the "smart" battery, however, it's still a LiPo battery at it's core...

I often wonder if all the "It fell from the sky for no reason" posts may have something in common...
(Damaged battery for excessive discharging)

Currently, I'd never even consider discharging the Phantim battery to the levels that DJI say is "ok"..

I'd love for someone to show me that eveything I've learned up till now about LiPos was BS...
Any Takers??

Thanks for your time and input!
JGT
2016-9-19
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DJI-Ken
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I've always discharged LiPos down to 20%.
DJI knows what they are doing and I've had batteries last close to 200 flights and still work fine.
I never got that with my old Hobbyking LiPos.
2016-9-19
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stuka
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DJI-Ken Posted at 2016-9-20 05:14
I've always discharged LiPos down to 20%.
DJI knows what they are doing and I've had batteries last  ...

I believe the JI has that 20% safety margin built into the Battery electronics. not sure what the actual capacity left is at say 30% on the monitor in Go.
2016-9-19
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JustGoThere
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Thanks Ken for the reply...
It really doesn't answer my question, "DJI knows what they are doing", and, I'm not doubting your usage...
(I have several LiPos that are still going strong after 2 years, I get that...)

I'm really looking for some type of "factual" info concerning LiPo usage and discharge limits to verify the facts..

thanks!
JGT
2016-9-19
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DJI-Ken
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JustGoThere Posted at 2016-9-20 05:31
Thanks Ken for the reply...
It really doesn't answer my question, "DJI knows what they are doing", a ...

The batteries do not discharge to zero. I think if you fly a battery to zero (I have many times for testing) that there's still charged in the battery.

2016-9-19
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Aardvark
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I discharge to 30% then land, and they're still above 3.7v per cell.

Shouldn't that not read "Don't use more than 80% charge" ?
2016-9-19
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JustGoThere
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Aardvark Posted at 2016-9-19 16:37
I discharge to 30% then land, and they're still above 3.7v per cell.

Shouldn't that not read "Don't ...

no....LOL..... only use 20% of the battery... so that 80% of the charge is left in the battery (hense the 4 - 4.5 minute usage time)
2016-9-19
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JustGoThere
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DJI-Ken Posted at 2016-9-19 16:36
The batteries do not discharge to zero. I think if you fly a battery to zero (I have many times fo ...

Thanks ken... I'm guessing there's a safety % left over when it registers zero...
2016-9-19
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Aardvark
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JustGoThere Posted at 2016-9-19 22:31
Thanks Ken for the reply...
It really doesn't answer my question, "DJI knows what they are doing", a ...

One piece of factual information is that most here will fly their batteries to 30% (The first battery low warning), with some taking them closer to the 10% 'critical' point (the aircraft will land itself).

I checked the 80% rule you refer to:-

"THE 80% RC LIPO BATTERY RULE TO THE RESCUE!
A very good rule to follow here is the "80% rule". This simply means that you should never discharge a LiPo pack down past 80% of its CAPACITY to be safe. For example, if you have a 2000 mAh LiPo pack, you should never draw more than 1600 mAh out of the pack (80% x 2000). This is assuming a healthy pack as well that has the full 2000 mAh capacity (as packs age, their capacity drops). "

So you can run them down to 20%.

That's an extract from Here

Does that answer the question :-

"I'd love for someone to show me that eveything I've learned up till now about LiPos was BS...
Any Takers??"


2016-9-19
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billwish76
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i have several lipo pwrd things.phone is main one. do you always charge your phone when its down to 80%.

my ecig and flash lights use same battery i bring those down to 3.3-3.5. the plus my rc cars n drones..  cheap rc lipos dont last. if its in like a non computerized unit and brought way down like 2v per cell yeah it can toast it.

all the readin ive done plus experience. stay above 3.3 and your good.

see iv also read to only charge to 4v to preserve the lipo. but also lipos have less v drop then nicd or nihd
2016-9-19
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Geebax
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Aardvark Posted at 2016-9-20 08:05
One piece of factual information is that most here will fly their batteries to 30% (The first batte ...

This information is correct, it is not a case of only using 20% of the available charge, you can use 80% of the available charge. The key to having long lasting LiPOs is to use closely matched cells, to avoid damage during use.

Also, it is a matter of common sense, what possible good would a battery be that had only 20% of its capacity available for use?

2016-9-19
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tkerling
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You are confusing the scale on the DJI battery with the full scale of a LiPo. The 0 - 100% scale is NOT 0 -100% of the battery's total capacity. The 0 - 100% is over the allowed depletion of the DJI battery. A fully discharged 0% reading on the DJI battery is probably close to leaving around 80% capacity in the battery.
2016-9-19
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Aardvark
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tkerling@gmail. Posted at 2016-9-19 23:43
You are confusing the scale on the DJI battery with the full scale of a LiPo. The 0 - 100% scale is  ...

Absolute rubbish !!!
2016-9-19
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EdM
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I think everything you have learned or are claiming to have learned is nothing but pure BS.    Be gone troll!
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Geebax
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tkerling@gmail. Posted at 2016-9-20 08:43
You are confusing the scale on the DJI battery with the full scale of a LiPo. The 0 - 100% scale is  ...

Ridiculous, where did you learn about batteries?
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JustGoThere
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WOW! Sorry I asked a question....
I didn't realize that if you don't know something, and ask about it here, you just get the crap kicked out of you..

(Edm) - don't sweat it, I won't ask anything anymore...this obviously isn't the place to ask technical questions concerning the product

It seemed like a nice helpful forum here from most of the posts I've read, but it's obviously misleading..
Everyone try and have a good day...and just forget I asked...
2016-9-20
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DJI-Ken
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JustGoThere Posted at 2016-9-20 05:41
Thanks ken... I'm guessing there's a safety % left over when it registers zero...

Yes, there's still charge left in the battery otherwise it would be damaged.
And a Phantom is not going to fall from the sky from using most of the capacity of the battery.
It will go into "Auto Land" if you keep cancelling the low battery RTH and will slowly land where it is.
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DJI-Ken
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JustGoThere Posted at 2016-9-21 01:24
WOW! Sorry I asked a question....
I didn't realize that if you don't know something, and ask about i ...

Sorry, other members can be over critical.
This forum is for users to come seeking assistance no matter how basic or advanced their questions are.
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Aardvark
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JustGoThere Posted at 2016-9-20 18:24
WOW! Sorry I asked a question....
I didn't realize that if you don't know something, and ask about i ...

Presumably somewhere in the posts (not all directed at you you'll note) you found the answer you were looking for.

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JustGoThere
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Aardvark Posted at 2016-9-20 12:36
Presumably somewhere in the posts (not all directed at you you'll note) you found the answer you w ...

thanks! it at least leads me to ask more questions about the Lipos...
(There's just not that much info concerning the subject online.. )

(Ken) Thanks so much!
(Ardvark) Thank you also!
2016-9-20
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kdcox
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<<== old helicopter guy too, and I as well learned the 80% rule, just the other way around from the original poster:  USE 80% of the charge, i.e. you could safely use 1600ma of a 2000ma lipo, i.e. dont go below 20% remaining capacity.  I've done it thousands of times and it seemed to work well.  my assumption is/was that, as someone above said (almost) that when the DJI go battery meter reads ZERO that there is likely around 20% charge remaining.  in practice I don't really give two hoots, cuz ive charged 3 of these bad boys many times and still can fly for 20+ minutes of blissful elative fun!

I have wondered how the ingenious dudes at DJI can wring almost 25 minutes out of a 4800 plus mah battery, when the best I can get from a 2200mah heli lipo is about 4 minutes, as does the OP.
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JustGoThere
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Thank you for re-asking in this way... I guess I just over stated the question...

So it's really, how do they get that kind of time out of the Lipo?
Not doubting DJI for 1 second, just the question about discharging for that kind of time frame is the real question I'm searching for...

perhaps the Phantom motors, don't draw the current that the Heli's do (my 700 will pull in excess of 145 amps at times)
Thanks!
2016-9-20
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EdM
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JustGoThere Posted at 2016-9-20 13:47
Thank you for re-asking in this way... I guess I just over stated the question...

So it's really, ...

Now that you have edited your first post it makes more sense plus you are trying to relate it to larger RC copter.  Sorry we got off on the wrong foot, my bad.   
No way to compare.   First thing is yes there are 4 motor vs 1, but they are much smaller .   Second if you figure the area of the blades and the pitch I think you will find it to be much smaller also.   I think the Esc's would fry before they could get to 140 amps.

My longest flight has been over 21 minutes while slowly covering about 2 miles doing video's the whole time.  I know I still had plenty of battery left but don't remember the percentage.   Now cutting up in Atti mode, constantly asking for all it had, would most likely bring it back to the 18 minute range.
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Mark97564
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He didn't ask a question, he came here making a foolish comment like he knew it all wanting people to dare to prove him wrong, that's what happend..  Everyone knows you leave 20% in a lipo if you want it to last, 10% will even get you a nice life off of a lipo...  3.5 volts loaded is where ya want to stop, 3.4 at max...  Which is a whole lot compared to the 50% of a Agm battery or 40% of a deep cycle Agm
2016-9-21
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MartP3
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Justgothere keep posting as i,m also interested to find out and hence gain maximum uses from lipo batteries.
Ignore the neg comments and abuse hopefully the moderator will sort those?

I read that every 3 months p4 battery should be fully discharged. What % is fully discharged I'm wondering.
2017-1-20
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Phantom3ProPilo
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MartP3 Posted at 2017-1-20 05:20
Justgothere keep posting as i,m also interested to find out and hence gain maximum uses from lipo batteries.
Ignore the neg comments and abuse hopefully the moderator will sort those?


To 7-8% every 20 charge cycles
2017-1-20
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adrian8891
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I think, that DJI has implemented to the batteries function that prevents from over discharge the battery.

I got mine 3 batteries - every time I fly to about 20-30% left, and on every 10th flight I discharge them to 0% by start them in drone and leave for a few hours. Drone will power off as soon as battery level is 0%. Then I charge to full.

Is it so bad for batteries?
2017-1-20
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SkysurferTony
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Geez,

Where is the brotherhood and hospitality folks, I thought the question was interesting and might be informational to some folks.

Smart Battery® who is am Mfg. of lithium batteries says that advanced lithium technology will provide you with 2000 complete charge and discharge cycles at 80% DOD.
After 2000 cycles, you will still have over 80% of usable energy left. Pretty much in line with what has already been stated about the dji except the cycles would probably vary.
Example:  One 12v 100ah battery, after being discharged 80% for 2000 cycles, is now a 12v 80ah battery.
Of course this is in reference to their commercial batteries but I think we could expect to see similarities in the dji lithium batteries.

So to the point of the original post, I think he was saying it might not be such a great idea to take it down the 10% critical level which is a valid point.
Also stated, it seems most experienced users are bringing it back when it hits 30%, which conforms to not discharging more than 80%.
Based on what I've read I may set the critical at 20% just to be safe, even assuming there is some reserve at zero.
It would be interesting to calculate the mah draw and compute the actual % of mah left when you get to 30%, to conclude if indeed there are reserves built in.
2017-1-20
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AG0N-Gary
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I think the most important part of this has been overlooked.  While you're flying, keep an eye on your individual cell voltages.  As the battery discharges, the cells may or may not stay balanced (likely not).  Don't let any one cell get below 3.0 volts before shutting down, or it will be damaged and you'll loose some life expectancy.
2017-1-21
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Quamera
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SkysurferTony Posted at 2017-1-20 09:35
Geez,

Where is the brotherhood and hospitality folks, I thought the question was interesting and might be informational to some folks.

Wow, 2000 cycles, that's more than I was expecting. I guess that is assuming the battery hasn't spent much time fully charged at higher temperatures or too long at a low state of charge. Can anyone confirm they have reached 2000 cycles or more from a Phantom battery. Even a reading of "Battery Life" from the battery after a significant number of cycles would be good to know.
2017-1-21
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Quamera
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AG0N-Gary Posted at 2017-1-21 21:12
I think the most important part of this has been overlooked.  While you're flying, keep an eye on your individual cell voltages.  As the battery discharges, the cells may or may not stay balanced (likely not).  Don't let any one cell get below 3.0 volts before shutting down, or it will be damaged and you'll loose some life expectancy.

Another reason to keep a close eye on them is because the DJI battery management also monitors them and if one cell voltage drops lower than the others it will firstly throw up a warning then if it drops even further it will limit the battery output to avoid a catastrophic failure.

That is the best option to stop the aircraft falling out of the sky but if the operator doesn't realize until that point that their Phantom is fighting a stiff breeze up top then they have a problem that RTH isn't going to fix (if the aircraft is downwind).
2017-1-21
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Quamera
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adrian8891 Posted at 2017-1-20 06:31
I think, that DJI has implemented to the batteries function that prevents from over discharge the battery.

I got mine 3 batteries - every time I fly to about 20-30% left, and on every 10th flight I discharge them to 0% by start them in drone and leave for a few hours. Drone will power off as soon as battery level is 0%. Then I charge to full.

Someone from DJI might like to confirm this but my understanding is that discharging Phantom batteries down to DJIs 0% level (actually there is still some charge left that shouldn't be used) isn't beneficial and isn't recommended anymore. Deep cycling is a relic left over from the NiCd and NiMH days that isn't applicable to any of the modern Lithium chemistries.
2017-1-21
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