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Big Battery Cell Variations
1220 18 2015-8-17
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AlmostTan
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Has anyone used healthydrones.com to analyze your flight logs?

I just uploaded a bunch and in doing so realized that one of my batteries (indicated by the serial number) has been repeatedly displaying large/abnormal cell variances during flight.

Here is an album of some of the battery logs.

I have an e-mail into Advexure where I bought the batteries asking for advice on how to move forward, as it seems through multiple recharges won't bring the battery in line.
Funny thing is I periodically check during flight but there's no way to monitor the entire time you are flying.

DANGEROUS/SCARY if you ask me.
2015-8-17
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jimcloud74
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Yes it tis. I just noticed that one of my new bats that has only been charged 9 times shows a 92% battery life left and some minor variances in cell values. I bled it down as DJI says to, you know, the 8% deal until it wouldn't power up. I charged it, and to my amazement, now it reads 100% I will be eyeing that one from here on out however. I have another one, the original that came with the unit, still reads 100%. It has been charged 60 times. I guess the app reads cell voltage and calculates life based on differences? I would like to know. Also, I noticed while I fly that the voltage on the main screen alternates between green and orange sometimes. It mainly does the orange color when I put some demand on the battery after I have been flying for a while. Any ideas A?


I got this reading on my "problematic" bat. I guess the problem is solved now...
Bat.JPG
2015-8-17
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Willie Wonka
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interesting !!! thanks for bringing it up, and also put the voltage on the main screen with the percentage and watch for it if it starts dropping fast as it always shows the lowest cell, and if it starts dropping fast you better be dropping the phantom on the ground fast before the battery cuts off completely.
2015-8-17
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rayrokni
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from what i quickly saw it seems the worst battery has a variation of 2% on that flight.
like anything else made there is an allowable variation tolerance, i have been trying to find out what that is for the P3 batteries but so far havent been able to.
i keep a record of all the battery cells on excell (just easier to quickly see the overall average health of each cell through multiple recharges) and the worst in mine was just under %2 on one instance and then i look at the average variance over a number of recharges and i can say that they are improving. i dont know if %2 percent variance is dangerous or not since i dont know what the allowable tolerance is, but if it gets continually worse after each recharge then i would say that is dangerous and stop using that battery.
have fun and good luck
2015-8-17
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AlmostTan
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Thanks - I just spoke w/ the developer of the website and he says the more data that people upload the more he can normalize it to help tell what is normal variance.  Right now w/ the little amount of data he said that he wouldn't extract too much meaning from it/run to returning the batteries.

He should have this data analysis complete within the next couple of days.

rayrokni thanks for sharing the 2% data.  Makes me feel better.  I'm going to keep a close eye.
2015-8-17
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rayrokni
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AlmostTan Posted at 2015-8-18 13:26
Thanks - I just spoke w/ the developer of the website and he says the more data that people upload t ...

just keep your own battery log, when i turn on p3 with a fully charged battery i go to the battery health window and do a screen shot( wait till u see the number of charges, sometimes it takes couple seconds for it to show up). i then enter the date , and all cell voltages and the number of times it has been recharged and heath %. i also mark on there every 20 recharges or so if i do a discharge to 8% or less as advised by DJI.
i know everyone is jittery with battery health, and rightly so
2015-8-17
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jimcloud74
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AlmostTan Posted at 2015-8-18 13:26
Thanks - I just spoke w/ the developer of the website and he says the more data that people upload t ...

I sampled flights all the way back to may and I had VERY few flights that didn't have this variance. I guess that we will have to keep uploading to build the database.
2015-8-18
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gregg1r
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jimcloud74@yaho Posted at 2015-8-18 23:30
I sampled flights all the way back to may and I had VERY few flights that didn't have this varianc ...

Jim, I've been playing with lithium ion batteries for close to 6 years. Mostly in high powered hand held search and spotlights.

The cells offered as high drain are available from10 amps up to 35 amps. The higher the amperage draw, the more heat generated and the shorter the battery life. Also, high drain cells don't have high capacity.

If you look at other lithium polymer batteries used, you'll see that some are available with much higher watt hour rating. The problem is that they are also larger and heavier than what's used in the Phantom.

Try running the Pilot app battery monitor and run full speed for a minute and watch the voltage sag. It will take a minute of so for the voltage to come back up. The higher the battery capacity the faster the recovery and the slower the sag.
2015-8-18
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jimcloud74
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gregg1r Posted at 2015-8-19 01:04
Jim, I've been playing with lithium ion batteries for close to 6 years. Mostly in high powered han ...

I noticed that. Thanks for your input. The new battery monitoring is awesome as you could never really watch it very well with the P2V platform. I guess it is a double edged sword as it gives more room to worry. After looking through multiple flight logs I have noticed that the batteries that I have not cycled down below 20% show more variances in the flight log. So is DJI just trying to get us to buy batteries sooner or are the small variances within normal limits. My first battery that came with the bird is 100% life with 60 plus discharges with practically no voltage variances. I want to do what is the best but don't expect theses bats to last forever. Thanks Gregg for your input.
2015-8-18
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AlmostTan
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jimcloud74@yaho Posted at 2015-8-19 01:40
I noticed that. Thanks for your input. The new battery monitoring is awesome as you could never re ...

Interesting. My battery that is throwing variances has never been below the 35% mark. Maybe it needa a little flexing.
2015-8-18
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jimcloud74
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AlmostTan Posted at 2015-8-19 02:20
Interesting. My battery that is throwing variances has never been below the 35% mark. Maybe it nee ...

Yeah. The healthiest battery I have is the first one that has been recharged the most and been run down to the lowest level. It goes against the grain of all the elder lipo gurus advice. As I said earlier, the battery that showed 92% life corrected to 100% after the power cycle AND gave me no errors the next flight according to healthydrones. It is going to be interesting to watch. Also, I wonder if these errors are more prevalent when you fly more aggressively.
2015-8-18
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gregg1r
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AlmostTan Posted at 2015-8-19 02:20
Interesting. My battery that is throwing variances has never been below the 35% mark. Maybe it nee ...

You should try conditioning your battery and then recharging.

The Pilot app gives you the ability to change the self discharge rate, so for this time, select the fastest discharge. Then pop the battery back int the Phantom and see what the display shows. You want it to slowly discharge to below 8-10%.

After you get it low, recharge and look at the displayed capacity. It should be 5% or higher than when that same battery was fully charged.

It would have been nice if DJI allowed you to lower the charge current, but then again, too many variables for most people.

I use a Accucell 6 charger for my lithium polymer batteries. It has the ability to charge at .5 amps which keeps the battery cool. Another nice feature is the capacitance testing where I can discharge at up to 10 amps.

The other thing about these batteries is that the PCB used to keep the battery from over charging or discharging can go bad. Nothing you can do if the PCB fails. If the PCB were to fail, the Pilot app would show zero volts for one of the cells.
2015-8-18
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jimcloud74
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gregg1r Posted at 2015-8-19 02:58
You should try conditioning your battery and then recharging.

The Pilot app gives you the ability ...

Hey Gregg. I am having trouble finding the "self discharge" rate in the app. Can you help? You don't mean "time to discharge" do you?
2015-8-18
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gregg1r
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jimcloud74@yaho Posted at 2015-8-19 03:34
Hey Gregg. I am having trouble finding the "self discharge" rate in the app. Can you help? You don ...

Yes Jim, I am referring to the rate of discharge(how many days it holds the charge)  that the app sets before the battery depletes it's self if you haven't used it.
2015-8-18
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rayrokni
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jimcloud74@yaho Posted at 2015-8-19 01:40
I noticed that. Thanks for your input. The new battery monitoring is awesome as you could never re ...

jim as per dji you are supposed to drop to %8 or below every 20 charges not 20%.
2015-8-18
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rayrokni
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AlmostTan Posted at 2015-8-19 02:20
Interesting. My battery that is throwing variances has never been below the 35% mark. Maybe it nee ...

there is your problem in your own words. as per DJI you are to drop to %8 or below every 20 charges!!!
2015-8-18
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AlmostTan
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rayrokni Posted at 2015-8-19 04:39
there is your problem in your own words. as per DJI you are to drop to %8 or below every 20 charge ...

The battery is only showing 5 charge cycles in the app. In reality its probably 10.
2015-8-18
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jimcloud74
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rayrokni Posted at 2015-8-19 04:38
jim as per dji you are supposed to drop to %8 or below every 20 charges not 20%.

Yeah. I always did that with my P2V+. I had one battery fail sooner than I thought it should have. All my Lipo flying buddies mouthes dropped when I told them what DJI advised. They could not believe that they advised to run a bat down to where it would not power up. (even every 20 times) It makes me hesitant but obviously there must be some truth to how DJI recommends. The battery that I have "mistreated" (according to my airplane buds) by running down below 20% has the best stats.
2015-8-18
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jimcloud74
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gregg1r Posted at 2015-8-19 04:33
Yes Jim, I am referring to the rate of discharge(how many days it holds the charge)  that the app  ...

Gotcha Gregg. Thanks!
2015-8-18
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