Please select Into the mobile phone version | Continue to access the computer ver.
Understanding the Inspire battery-sudden charge drop phenomenon.
12Next >
5099 45 2015-5-1
Uploading and Loding Picture ...(0/1)
o(^-^)o
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

I am in the early stages of collecting data from flights using each of my 3 TB47's, because it seems that many people are experiencing battery issues. When flying over water or in rugged terrain, a battery failure or an unexpected drop in remaining flight time could be fatal to the bird. I invite people with technical knowledge to chime in because I have very little RC experience, but I think we people on the forum might solve this problem with collective effort.

I have been most fortunate to have no issues whatever with the Inspire system but i read the forums religiously to keep abreast of potential issues, especially after new firmware releases. I invite other like-minded individuals to share their battery data so we all might benefit and potentially solve a very serious situation, passing what we have learned to each other and DJI.

I have included an Excel template for basic battery data collection as a shared dropbox file (link at end of post). Any interested parties please feel free to contribute their data also so we can compile and understand this phenomenon of sudden percentage drop during flight.

The hypothesis I am testing relates to the nature of the LiPo packs and their on-board control circuitry, potentially affected by the battery firmware. My understanding (though shallow) is that the packs have protection circuitry that shut down the discharge of individual cells when a critical voltage level is reached in order to prevent over-discharge and damage to the cell itself. The software recalculates the estimated battery flight time and percentage charge as the battery discharges, based on data from all 6 individual cells. The continuous updating and recalculation may explain what we are reading about with the sudden-drop phenomenon. I have been flying my packs down to the critical battery/RTH threshold at which point I hold the bird in a low-altitude forced hover near my Home Point until the battery level shows <5%. I have my controller set up so one of the back buttons brings up the detailed battery screen so I may monitor frequently the cells. I record the battery info pre and post flight, then review the flight/battery percent on my remote (at 4x speed). I have noticed a very smooth drop in battery percentage to a certain level at which time the percentage life drops abruptly. In my case, this usually occurs around 7-8%, with a sudden drop to 2-3% at which time I land immediately. At that point one or two of the individual cells is showing at or below the under-voltage cutoff and has been shutdown by protection circuitry.

It is likely that when an individual cell is shut down, that cell can no longer contribute to the packs voltage (or current). At that point, the 3.50V drops out, the pack's voltage drops abruptly and the recalculation reveals a substantially reduced remaining flight time. Early data supports this as a possible cause of the rapid drop phenomenon. My individual cells are within 0.02V of each other at full charge, but the spread is much higher near full discharge (up to 0.09V in one), and the same cell in the individual pack always shuts down first.

If someone who had a battery pack, with an individual cell that had even greater variation in discharge characteristics, were to try this experiment, it is POSSIBLE that their battery pack might show sudden drop at a much earlier time, maybe dropping the pack percentage from 25% to less than 10% instantly when the over-discharge shutoff pulls that individual cell offline. Please post your battery data so we might all learn from it.

Inspire Battery trial


2015-5-1
Use props
Fred D
Second Officer
Flight distance : 56181 ft
Canada
Offline

Your link doesn't work
2015-5-1
Use props
Bob Marley
Second Officer

United States
Offline

All 4 of my lipo packs work perfectly.
I think you are making a fuss over something that is only happening to 1 of 1000 people -

Maybe those people were NOT taking care of their packs?


Bob Marley
2015-5-1
Use props
PeteGould
Second Officer

United States
Offline

Bob Marley Posted at 2015-5-1 21:08
All 4 of my lipo packs work perfectly.
I think you are making a fuss over something that is only hap ...

Out of curiosity - are you running tb47's or 48's or a mix?
2015-5-1
Use props
Bob Marley
Second Officer

United States
Offline

PeteGould Posted at 2015-5-1 22:17
Out of curiosity - are you running tb47's or 48's or a mix?

stock47 plus 3 48's, (all 4 acting identically well)


Bob
2015-5-1
Use props
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

I'm not making a fuss at all, but if 1 in 1000 people don't crash their $3000 machine, it' s a worthwhile endeavor. Besides, we might learn something unexpected. I don't plan to deep discharge my packs repeatedly to <5%, it's probably not good for them. I will do it a few times in the interest of calibrating them and learning my flight time limits on the individual packs. I HOPE that some of the unfortunate few who ARE having problems, collect some data and present it so we can all know if it is a sporadic problem related to firmware/software, or if they just have a bad cell in their packs. I don't know whats wrong with the link; Dropbox® links works before the forum redesign. I
ll just add a screenshot and folks can do their own spreadsheet.
2015-5-1
Use props
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

/Users/rbimd1/Desktop/Screenshot 2015-05-01 10.20.45.png
2015-5-1
Use props
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

https://www.dropbox.com/s/0n2tbj ... al%20copy.xlsx?dl=0
2015-5-1
Use props
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

Finally got it to work

2015-5-1
Use props
FictitiousPerso
Second Officer

United Kingdom
Offline

Rbimd Posted at 2015-5-1 22:25
I'm not making a fuss at all, but if 1 in 1000 people don't crash their $3000 machine, it' s a worth ...

Right with you there

But when you present it? will this be to DJI? if it is i feel you'll be wasting your time.

Good luck to you though
2015-5-1
Use props
GrahamJ
Second Officer

Australia
Offline

Don't have Dropbox account.....but anyway, yes, these batteries are sensitive, and many folks seem to report issues.  I have had no issues, and run Tb-47 and 48 together.  I run them down till circa 15% each time, and occasionally do the "deep discharge" thing.  Other than that, they work just fine...  (Touch wood
2015-5-1
Use props
Acidsnow
Second Officer
Flight distance : 13 ft
Canada
Offline

This is a good idea, sudden loss of power is VERY dangerous, crashes can cause of a lot of damage and injury.  If this information helps prevent even 1 injury it is worth collecting . . . DJI should really be monitoring this situation . . .
2015-5-1
Use props
PeteGould
Second Officer

United States
Offline

FictitiousPerso Posted at 2015-5-1 22:34
But when you present it? will this be to DJI? if it is i feel you'll be wasting your time.

You're certainly right about that but if he determines that there is a pattern, users can learn from it directly.

Thus far there appear to be two suspect issues that may be associated with risk factors: the TB47, and flying on a partially-charged pack, i.e., flying, landing, shutting down - and then taking off and flying again on the same pack.  If there turns out to be a strong relationship between these issues, people can avoid doing it and perhaps avoid an accident.

It would also be interesting, since this has proven to be an area of controversy, whether deep-discharging of packs plays a role - that is, if you are more likely to have one of these events if you DO deep-discharge on DJI's recommended schedule or if you DON'T.  Again, while DJI may ignore the data, users can certainly learn from it.
2015-5-1
Use props
PeteGould
Second Officer

United States
Offline

Bob Marley Posted at 2015-5-1 22:25
stock47 plus 3 48's, (all 4 acting identically well)

I seem to have seen a lot more 47s involved in incidents than 48s.  We have four 48s in addition to the stock 47 and fly them exclusively on mission-critical projects.  The 47 is used only for practice and testing.  Though we haven't had a problem with it either.
2015-5-1
Use props
Acidsnow
Second Officer
Flight distance : 13 ft
Canada
Offline

the first deep discharge on my TB47 showed a drop of 2% of total battery life.  My battery life is now at 98% after 11 charges, and 1 deep discharge.
2015-5-1
Use props
Rockeyes
lvl.4

United Kingdom
Offline

Has anyone measured the voltage after completely running down a power pack as per the deep cycle instructions prior to the recharge? If so what was the voltage?
2015-5-1
Use props
PeteGould
Second Officer

United States
Offline

Acidsnow Posted at 2015-5-2 00:34
the first deep discharge on my TB47 showed a drop of 2% of total battery life.  My battery life is n ...

This is another question for DJI, but I would bet you a nice meal that the remaining-battery-life indication is not really an indication of overall HEALTH, but the amount of USAGE.  Perhaps we should all track this for awhile and see if those who deep-discharge their packs end up with a different "remaining life" indication than those who do not, for the same number of charge cycles.
2015-5-1
Use props
Rockeyes
lvl.4

United Kingdom
Offline

PeteGould Posted at 2015-5-2 02:29
This is another question for DJI, but I would bet you a nice meal that the remaining-battery-life  ...

That makes sense after all how do you measure the health of one of these packs? Usage is is simple. Maybe that's a question online tech support can help with?
2015-5-1
Use props
Grimtheviking
lvl.4
Flight distance : 2909193 ft
United Kingdom
Offline

This is a great idea,
especially after the latest reports of drastic battery level drops when landing and 2nd take off with the same battery.. (I will not be doing that 1, due to that report and threads like this)
I am already following my charging and discharging, Yesterday after a deep discharge (3% ) of a TB47 remaining life went down to 98%, 24 charges/2 discharges.
I think this is maybe what it should be showing though ????  Everything flew as normal and as usual, impressive...
Still really pleased with my purchase. as are most, but a lot of good has come out of posts like this.

Regards
Mike.
2015-5-1
Use props
PeteGould
Second Officer

United States
Offline

Rockeyes Posted at 2015-5-2 03:00
That makes sense after all how do you measure the heath of one of these packs? Usage is is simple. ...

Quite possibly.  Next time one of us finds ourselves on the phone with them (probably don't want to brave the hold queue just for this!) it's probably worth asking.
2015-5-1
Use props
Rockeyes
lvl.4

United Kingdom
Offline

I'm asking the question via the online chat now.

Q- 'Is the remaining-battery-life indication is an indication of overall HEALTH, or the amount of USAGE?'

A- overall health

A- the amount which could be used

Q- Could you tell me how this is measured, for example is it measured on deep cycles?

A- yes

Q- So the amount of deep cycles carried out is registered as battery health?

A- Support checking, please wait, thank you.

A - Yes



2015-5-1
Use props
Rockeyes
lvl.4

United Kingdom
Offline


Thank you DJI support
2015-5-1
Use props
PeteGould
Second Officer

United States
Offline

So how are you interpreting that?
2015-5-1
Use props
Rockeyes
lvl.4

United Kingdom
Offline

PeteGould Posted at 2015-5-2 09:57
So how are you interpreting that?

Going by the questions and replies from tech support, battery health is monitored by the amount of deep cycles carried out on the pack. So therefore deep cycling is directly proportionate to the indicated health on the app. This would also fit in with reports of loosing 'indicated battery health' after deep cycling.

Here's the big however, I'm not convinced.

I can see monitoring these these packs by the above method maybe the cheapest and simplest option, but fail to see how that can demonstrate the condition of the battery pack. It would really be just a glorified timer. There are several ways to test a battery but in real terms they are often used together. The First method is a CAP test which is the true capacity of the battery. This is where the battery is fully charged and a load is applied which is based on its intended use and timing how long it can supply that power for. If this method was used in some of modified form you could up with trouble using a partially depleted battery at a start of a flight.

The other form of testing could be an internal resistance check. This is carried out by using a fully charged battery and measuring its voltage (Unloaded volts= V1). Then placing the battery on a known load again based on the 'normal' expected requirement and reading the voltage again (Loaded volts=V2). The difference between the two is the voltage drop. The amount of current been drawn (Amps=I) at this time is also recorded.
V1-V2 = Voltage drop, multiply this by the  Amps and this gives us the total internal resistance in Ohms.

The internal resistance method would have been my guess on how its done and it would also explain how the batteries can self discharge depending on the time set. Hence my lack of confidence in DJI's reply.

Either way I personally would avoid starting a flight without a fresh battery or doing any deep cycles as much as possible and feel there is a glitch in the firmware.
2015-5-2
Use props
PeteGould
Second Officer

United States
Offline

Of course the CAP test is the only one that will REALLY tell you where you're at - measuring loaded output vs unloaded is a shorthand method that requires extrapolating from a known baseline (i.e. Knowing a "healthy" V2).

Now here's MY concern regarding DJI's method.  We know lipo life is finite.  You get a certain number of charge cycles and the battery is used up (NOT deep discharge cycles - charge cycles in total).  If DJI factors this in by decrementing the "battery health" number with every deep discharge cycle - not by evaluating anything but simply by a fixed percentage for every deep discharge, with the assumption that a deep discharge represents a total of ten charging cycles - consider what happens when you do not deep-discharge on DJI's schedule.  Your "battery health" indicator may indicate far more remaining battery charge cycles than you actually have.  And you may discover this in the air when suddenly a fully charged pack only lasts eleven minutes and drops from 50% remaining to 19% remaining over ten seconds, then attempts low-batt RTH and crashes because it REALLY only had 6% and not 19.  THAT is my worry.  Am I right?  Who knows.  But I'm concerned.

This is the problem with this company.  All the other equipment I deal with has documentation written for professionals, complete with schematics, circuit descriptions and theory of operation.  If you want the answer to a question like this, it's in the book.  With this DJI stuff it's all a secret.  Questions to the company receive answers that are subject to interpretation.  You look at the answer and it clearly says do not deep-discharge as you are reducing battery life.  I look at the same answer and conclude that if you DON'T deep-discharge you may end up with a false sense of security about your remaining battery life and get bitten in the ass.

And there is no one to call for the DEFINITIVE answer.  Even the support guy in your chat didn't know: he had to ask someone.  Did he phrase the question properly when he asked, or did he foul it up and get the wrong answer?  We don't even know.

It's a very frustrating company to deal with, I must say.

And then you throw someone like Bob Marley into the works, with his absolute answers to anything he is asked (not based on actual knowledge of how DJI's implementation of this technology works, since only DJI employees have that, but on some mix of experience with unrelated previous gear, conjecture, and which way the wind is blowing) and visitors to this group have no idea who to listen to.

The fact that Tahoe deep-discharges HIS battery packs every ten cycles tells me that is the safe way to go if one wants help from DJI in the event of a failure.  But it would be awfully nice to have the definitive answer, and we still don't, IMHO.


2015-5-2
Use props
Rockeyes
lvl.4

United Kingdom
Offline

PeteGould Posted at 2015-5-2 21:26
Of course the CAP test is the only one that will REALLY tell you where you're at - measuring loaded  ...

Could not agree more on all points. The trouble as you say is that we are really poking around in the dark here without any suitable publications to go by. The problem is compound that with unhelpful forum 'noise' and a language barrier from what appears to be a company that appears unenthusiastic working with the users of their product.  The forum is a mess and therefore its struggle to try and keep up with any developments. I hope those Beta testers are having more luck.

Anyway back to subject. How confident are we that the battery is fully charged? After all a rapid voltage drop should be an indication of the point the battery being totally depleted. So if the battery wasn't being fully charged but indicated it was. We could expect the issues that are being reported.

Until we get some information that we are confident with, all we are going to do is chase our tails on this one. I would still like to know what the voltage is on a battery after being totally discharged as recommended by DJI. That alone would be a good starting point.
2015-5-2
Use props
PeteGould
Second Officer

United States
Offline

Rockeyes Posted at 2015-5-3 04:01
How confident are we that the battery is fully charged? After all a rapid voltage drop should be an indication of the point the battery being totally depleted. So if the battery wasn't being fully charged but indicated it was. We could expect the issues that are being reported.

The rapid voltage drop can indicate either of two things - either that the pack was not fully charged and is therefore nearing end-of-charge for that reason - OR - that the pack has reached end of life and will no longer properly hold a charge.

For the moment I'm simply following DJI's schedule of deep-discharges, watching the battery health indication within the app, noting any trouble indications in a given battery's history, and keeping an eye on voltage across the cells and looking for any discrepancies.

Oh - and having a hell of a good time flying the bird.  Let's not forget that.  
2015-5-2
Use props
Rockeyes
lvl.4

United Kingdom
Offline

'The rapid voltage drop can indicate either of two things - either that the pack was not fully charged and is therefore nearing end-of-charge for that reason - OR - that the pack has reached end of life and will no longer properly hold a charge.'

Agree agreed agreed. I'm going down the route of keeping these deep charges to a minimum and one flight one battery. Looking out for some tale tale signs as I do.

Last set of flights I did was purely to give the bird a shake down and in doing so booster my waning confidence in her.  Lets just say the flights were worth doing   Might dial in a tad of expo on a couple of axis and dial down the braking a stop. I recon that thing pulls 10g from max speed to letting go of the sticks.
2015-5-2
Use props
Fred D
Second Officer
Flight distance : 56181 ft
Canada
Offline

Just thought I'd throw in a couple of my observations for what ever they may be worth. I have 3 batteries that I use in order #1 came with the I1, #2 from DJI, #3 Amazon. Let me first state that I have had NO serious issues with my Inspire, glitches, a few but nothing I couldn't handle. A couple of days ago I was flying on #1 and got called away so I shut her down for about an hour with approximately 55% battery left. When I took off again later I was using the same battery without recharging it, I have "low battery warning" set at 30% when the warning goes off I generally fly close till I get "Critical Warning" at 15% then I land.
This time at 20% it went to "Critical Warning" and now it was 7% I landed and all was good. This same thing happened again with the same battery, where I shut her down part way through the charge and then hours later put her back up on the same battery, and the same thing happened. Only this time it went down to 4% and then I noticed that the "Battery Life" was now 92%. I have flown this same battery about 9 times since and have had no problems since, I still get approx. 15 minutes in the air (TB47).
I did it again today, I thought it would be OK because I only shut her down for about 10 minutes, this was battery #2, it suddenly dropped from about 20% to 7% and now the battery life is 94%. From now on I am only going to fly the complete charge, and if I have to shut down I'm going to recharge before I reuse that battery and see how that works out.
Hope this helps.
2015-5-3
Use props
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

Fred D Posted at 2015-5-4 11:20
Just thought I'd throw in a couple of my observations for what ever they may be worth. I have 3 batt ...

Fred D,

If you could kindly record the battery data on the spreadsheet before and after flight with the battery in question, your information is exactly the sort we need to analyze this problem. THX!
2015-5-4
Use props
Fred D
Second Officer
Flight distance : 56181 ft
Canada
Offline

Rbimd Posted at 2015-5-4 17:26
Fred D,

If you could kindly record the battery data on the spreadsheet before and after flight wi ...

I would, but I don't seem to be able to download it as a blank form to fill out.
It is already filled in or am I missing something
2015-5-4
Use props
Rockeyes
lvl.4

United Kingdom
Offline

Fred D Posted at 2015-5-4 11:20
Just thought I'd throw in a couple of my observations for what ever they may be worth. I have 3 batt ...

Well done Fred that information is priceless. Thanks for posting it up. I will try and get some time (and weather) to repeat what you did and log the results.
2015-5-4
Use props
arunmehta
Second Officer
Flight distance : 120909757 ft
  • >>>
Canada
Offline

from Battery University about Lipo (also Li-ION)  http://batteryuniversity.com/

Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The shorter the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine.
In LiPO There is no memory and the battery does not need periodic full discharge cycles to prolong life

Table 2 compares the number of discharge/charge cycles Li-ion can deliver at various DoD levels before the battery capacity drops to 70 percent. All other variables such as charge voltage, temperature and load currents are set to average default setting.

Depth of discharge
Discharge cycles
Table 2: Cycle life as a function of
depth of discharge
A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
100% DoD
50% DoD
25% DoD
10% DoD
300 – 500
1,200 – 1,500
2,000 – 2,500
3,750 – 4,700

Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion, a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC.

Temperature
40% charge
100% charge
Table 3: Estimated recoverable capacity when storing Li-ion for one year at various temperatures
Elevated temperature hastens permanent capacity loss. Not all Li-ion systems behave the same.
0°C
25°C
40°C
60°C
98%
96%
85%
75%
94%
80%
65%
60%
(after 3 months)

Most Li-ions charge to 4.20V/cell and every reduction in peak charge voltage of 0.10V/cell is said to double cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.00V/cell should deliver 1,200–2,000 and 3.90V/cell 2,400–4,000 cycles.

In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms. (See BU-808b: What causes Li-ion to die?) Table 4 summarizes the capacity as function of charge levels. All values are estimated.

Charge level(V/cell)
Discharge cycles
Capacity at full charge
Table 4: Discharge cycles and capacity as a function of charge voltage limit
Every 0.10V drop below 4.20V/cell doubles the cycle but holds less capacity. Raising the voltage above 4.20V/cell would shorten the life.

Guideline: Every 70mV reduction in charge voltage keeps 10% of usable capacity vacant
[4.30]
4.20
4.10
4.00
3.92
[150 – 250]
300 – 500
600 – 1,000
1,200 – 2,000
2,400 – 4,000
~[114%]
100%
~86%
~72%
~58%

Most chargers for mobile phones, laptops, tablets and digital cameras bring the Li-ion battery to 4.20V/cell. This allows maximum capacity, because the consumer wants nothing less than optimal runtime. Industry, on the other hand, is more concerned about longevity and may choose lower voltage thresholds. Satellites and electric vehicles are examples where the importance of longevity surpasses harvesting maximum capacity.

For safety reasons, many lithium-ion cannot exceed 4.20V/cell. (The exception is the high energy-dense NMC that charges to 4.30V/cell.) While a higher voltage boosts capacity, exceeding the voltage shortens service life and compromises safety. Figure 5 demonstrates cycle count as a function of charge voltage. At 4.35V, the cycle count of a regular Li-ion is cut in half.


Figure 5: Effects on cycle life at elevated charge voltages
Higher charge voltages boost capacity but lowers cycle life and compromises safety.
Source: Choi et al. (2002)

Besides selecting the best-suited voltage thresholds for a given application, a regular Li-ion should not remain at the high-voltage ceiling of 4.20V/cell for an extended time. When fully charged, remove the battery and allow to voltage to revert to a more natural level. This is like relaxing the muscles after strenuous exercise. Although a properly functioning Li-ion charger will terminate charge when the battery is full, some chargers apply a topping charge if the battery terminal voltage drops to a given level


LONGEVITY ISSUES:
The Dalhousie University in Halifax under Professor Jeff Dahn studied the longevity of L-ion by coulombic efficiency (CE). CE is a method that defines the efficiency with which electrons are transferred in an electrochemical system.

During charge, lithium gravitates to the graphite anode (negative electrode) and the voltage potential changes. Removing the lithium again during discharge does not reset the battery fully. A film consisting of lithium atoms forms on the surface of the anode called solid electrolyte interface (SEI). Composed of lithium oxide and lithium carbonate, the SEI layer grows as the battery cycles. The film gets thicker and eventually forms a barrier that obstructs interaction with graphite. (See BU-701 How to Prime Batteries)

The cathode (positive electrode) develops a similar restrictive layer known as electrolyte oxidation. Dr. Dahn stresses that a voltage above 4.10V/cell at elevated temperature causes this, a demise that can be more harmful than cycling. The longer the battery stays in the high voltage, the faster the degradation occurs. The build-up can result in a sudden capacity loss that is difficult to predict by cycling alone. This phenomenon had been known for some years and measuring the coulombic efficiency can verify these effects in a more scientific and systematic manner.



Discussion:

So it seems that DJI is giving wrong info about deep discharge.. it actually may damage cells. I think tyou may want to do it once to caliberate the battery BUT not needed each 10 cycles as the new firmware makes you do!!Field use revealed that the combination of heat and high voltage can cause more stress to Li-ion than harsh cycling.

Lithium-ion is a very clean system that does not need additional cycling  once it leaves the factory, nor does it require the level of maintenance that nickel-based batteries do. Additional formatting makes little difference because the maximum capacity is available right from the beginning, (the exception may be a small capacity gain after a long storage). Nor does a full discharge improve the capacity once the battery has faded. A low capacity signals the end of life. A discharge/charge may only be beneficial to calibrate a “digital” battery; it does nothing to improve the “chemical battery.” (See BU-601: Inner Working of a Smart Battery) Instructions recommending charging a new battery for eight hours do not cause harm but this is “old school,” a left-over from the old nickel battery days.


Arun Mehta




2015-5-5
Use props
Rockeyes
lvl.4

United Kingdom
Offline

Thanks for the information Arunmehta. I'm of the opinion that that deep cycling these batteries is doing more harm than good and am also concerned that starting a flight without a fully charged battery pack is possibly causing an accumulation of errors. Was hoping to get some data in today but high wind and rain is preventing further investigation.  So I will spend some time reading up on that link you've posted up on a smart battery.

Thanks
2015-5-5
Use props
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

Thanks Arun Mehta!  Battery University is a WONDERFUL resource. My battery packs showed noticeable loss of "Battery Health" after deep discharge to 2-3%. Fortunately, I have only performed this action once to calibrate the battery and convince myself of safe flying limits. I would beseech DJI to modify their recommendation of deep cycling every 10 charges or else provide US with detailed information why this must be done. I have only seen "sudden drop" with my packs at discharge levels so deep (7-8%) that the under voltage protection circuits for the individual cells are beginning to kick in. It is still my OPINION that those experiencing "sudden drop" in pack charge percentage occurring at HIGHER levels probably have:
(1) one or more individual cells (of the 6) in their packs goes to under voltage-protection, either from over-stress performance loss, or manufacturing deficiency (i.e in protection circuitry or the cell itself)
(2) bad battery-pack calibration or malfunctioning "smart battery" controller
(3) battery firmware issues (probably less likely, considering the rarity of the event)
At any rate, anyone experiencing the "sudden-drop" phenomenon at higher battery pack levels, please record and REPORT the battery information available on the battery diagnostic screen so we may all LEARN.
As I have become more paranoid about my battery health, I have set up one of the remote controller's BACK BUTTONS to be able to instantly show that screen information without having to dig through menus in a period of stress.
2015-5-5
Use props
Rbimd
lvl.4
Flight distance : 407710 ft
United States
Offline

Incidentally, I have noticed that at the very moment the pack is deep-discharged, if you check the battery diagnostic screen, the individual cell voltages can be VERY low, near 3.00-3.10 volts, but quickly recover within minutes to a somewhat higher level 3.40-3.50 volts when the motor is switched off. It may be important to record battery information as soon as possible after safely landing.
2015-5-5
Use props
rende
New

Germany
Offline

I had the Same Problem :@ Inspire Crash after Battery Drop:
2015-10-31
Use props
Capt_M
lvl.2

United States
Offline

A lot of good info!
I'm also wondering if anyone tried flying two batteries in parallel just connecting two power wires of each batteries together, I think this will eliminate sudden voltage drop..
2015-10-31
Use props
Capt_M
lvl.2

United States
Offline

rende@dreihunde Posted at 2015-10-31 19:58
I had the Same Problem  Inspire Crash after Battery Drop:
https://www.youtube.com/watch?v=uKJQhSS ...

36% to 7% ouch!
Lesson if you are at 120 m and see a drop to 7% - land ASAP, the less altitude you have, less energy you need to desipate
2015-10-31
Use props
JapanDave
lvl.2
Japan
Offline

Bob Marley Posted at 2015-5-1 22:08
All 4 of my lipo packs work perfectly.
I think you are making a fuss over something that is only hap ...

Your a dick. Am I making a mountain out of a mole hill? Depends on how big a dick you are.
2015-11-1
Use props
12Next >
Advanced
You need to log in before you can reply Login | Register now

Credit Rules