Battery Info
- Thread starter phototom1
- Start date
Hard to say from looking at a 33s flight data. If you have a longer flight you have made with the same battery, post that.
Already from your first flight ... that battery have had it's glory days, time to exchange.
LiPo batteries are fully charged when they reach 4.2v/cell, and their minimum safe discharge, is 3.0v/cell. 3.7v is pretty much in the middle, and that is the nominal charge of the cell.
If you look at your battery:
In the last 5sec of the flight you for the first had major cell deviations way above 0,1v, furthermore 2 of the 3 cells were under 3v which only that indicate damaged cells ... this with indicated 53% battery left
If I take on of my MA batteries:
Also indicating 53% left ... but I'm on the nominal voltage 3,7v. The cell deviation is also classified as minor (above 0,01) but well below what's called major (above 0,07v)
LiPo batteries are fully charged when they reach 4.2v/cell, and their minimum safe discharge, is 3.0v/cell. 3.7v is pretty much in the middle, and that is the nominal charge of the cell.
If you look at your battery:
In the last 5sec of the flight you for the first had major cell deviations way above 0,1v, furthermore 2 of the 3 cells were under 3v which only that indicate damaged cells ... this with indicated 53% battery left
If I take on of my MA batteries:
Also indicating 53% left ... but I'm on the nominal voltage 3,7v. The cell deviation is also classified as minor (above 0,01) but well below what's called major (above 0,07v)
Try launching with a fully charged pack if you hope to get a better indication of battery health/performance. The telemetry from a pack flown for less than a minute from around 50% SOC won't give you the full picture.
The full picture is in the other attached log from an earlier flight in 17,5C degrees in P-mode (low load circumstances), 99% to 28% battery.
Even then loads of major cell deviations ... this battery are shot, better to play safe with batteries behaving like this.
The telemetry from a pack flown for less than a minute from around 50% SOC won't give you the full picture. Do you disagree?
My comment didn't relate to the second log posted.
Looking at the second log I wouldn't be so hasty to sign the retirement papers for the battery.
For the second half of the flight deviations were of little to no concern. Health is reported by the BMS as 100% with reported capacity being close to as new spec.
I would keep an eye on it however there I don't think we have reason to say it is "shot". The fact Airdata has flagged 70mv cell deviation as "major" shouldn't given too much weight. The more accepted figure is 100mv plus.
@phototom1 What was the time duration between charging the battery subject of your second log posted and the flight?
Well ... my comments relates to a battery closing in to it's second birthday with all the facts provided.
A Lithium ion polymer that have been discharged under 3v ... not by little instead by 0,251v have been damaged. And adding to this the earlier flight showing that much major deviations consistent during 6 minutes all in warm temps under low load is really worrying, none of my 4 batteries do this.
But it isn't either you or I that will be paying for a possible near future total failure which certainly will cost much more then a new battery ... so I will play safe in my advise & let the owner make up his own mind what risks he's willing to take.
Taking a LiION cell down to 2.5V or below (resting) and leaving it for a few days will almost certainly result in irreversible damage. 3V (loaded) seems to be the typical considered min working voltage. The occasional dip below 3V is unlikely to be a major problem.
2 years old doesn’t seem to be the issue it once was with current chemistry. Many of us are flying phantom batteries from 2016 with only slightly reduced performance but great reliability.
From what is depicted in the flight records the battery should be closely watched (keep an eye on the in flight performance and logs). If the depicted deviations persist or increase then yes I agree it would be best retired.
Where are you getting that from?
This battery had many battery cell deviations that exceeded 100mv. Plus cell 3 consistently struggled to keep up whenever throttle up was applied.
OP has the final call in this, but if this was my battery I wouldn't fly with it. I would relegate it to on-ground duty.
The same place @slup grabbed the screenshots of the cell voltage plots- Airdata.
The battery health is reported as 100%.
Capacity is very close to new spec.
Reported charge cycles = 1.
Pack was manufactured in June 18.
If I was a betting man I and liked guessing my money would be on the fact that the battery sat around for a considerable period at a low SOC and cell 3 got close to critically low voltage. If that is the case the battery will never be any good.
The fact is though we don't know what the situation is from the available data and information.
The next flight it may be good. We don't have enough to say it's ready for retirement at this point.
I think that data is spurious. When ever I have uploaded and viewed someone else's flight log to my AirData account, the charge cycle invariably appears as 1.
Edit: Also take a look at this. Notice how battery voltage drops to 9.95V within the first few minutes of flight and how battery still reports 90% of capacity. Excellent example of how battery% can be very deceptive. Also note that battery voltage drops significantly with each application of extended throttle up because cell 3 is unable to keep up. I will bet a dollar and a half this battery will fail soon.
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That hasn’t been my experience.
If you have the inclination perhaps you could look at the log in the phantomhelp log viewer.
What is interesting in this case is that the deviations are reported as being unremarkable for the second half of the flight. Very uncommon behaviour for a pack having one bad (weak) cell.
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I will happily give you a txt file from my own logs to prove the point. Upload it to your AirData account and see how the charge cycle count comes out. Randomly selected txt file attached below.
P.S> Also, I edited my previous post, apparently while you were replying to it.
Ok- as you predicted I see the times charged (for your flight record) as 1. Interestingly last MAh reported for capacity is 0 and there is no temperature data. I have other flight records which do show cycle count >1 so not sure what the explanation might be for that.
Looking at the log you posted and that for the OP (assuming both AC are Mavic Air) the OP battery actually outperformed yours (flight time for % used) despite the seemingly poor cell balance performance by comparison.
Im sure you haven't missed my point- it is not possible to call this battery out as a dud without more information. The significant initial sag followed by recovery, seeming typical cell balance as the flight progressed and delivered flight time within the expected range are not suggestive of a dodgy cell.
For comparison, here is how it comes out when I view it from within my own AirData account - the charge cycle count reads 55.
The absence of temperature data is something I enquired about a long time ago and never got an answer. Interestingly, I get temperature data when flying with Litchi and I can see the temp readings by going into the battery menu in flight when flying with GO4. I don't know why temp readings are not included in the flight log data
Yes, I too fly an MA but there is a simple explanation to that; OP's takeoff altitude=215.6m asl, my altitude is 1819.9m asl. I have significantly reduced flight time across all my batteries due to the altitude.
I haven't missed that and agree a period of careful monitoring is important before anything can be concluded (normally). But I would personally not fly with a battery like that even based on what can be seen from this single flight. But that is me, I choose to err on the side of caution.
Prismatic
Well-Known Member
Last summer I had a Mavic Air battery fail in flight. Let me just say that’s an experience I wish never to repeat! (Luckily it was nearby and low, and although the tree it landed in ate a prop, the aircraft itself was unscathed.) Had it happened three minutes later, my MA would have been in a swamp.
This event convinced me to bump up my Airdata subscription to get full battery data. I could then see that the battery had been experiencing major deviations for several previous flights.
I took that battery out of service, and another one as well. The second one never failed but its signature was too similar to the one that did fail that I wouldn’t risk my MA with it.
I will never fly again with a questionable battery. I won’t gamble with catastrophe just to squeeze a few more flights out of a battery that’s plainly on its deathbed anyway.
This event convinced me to bump up my Airdata subscription to get full battery data. I could then see that the battery had been experiencing major deviations for several previous flights.
I took that battery out of service, and another one as well. The second one never failed but its signature was too similar to the one that did fail that I wouldn’t risk my MA with it.
I will never fly again with a questionable battery. I won’t gamble with catastrophe just to squeeze a few more flights out of a battery that’s plainly on its deathbed anyway.
Prismatic
Well-Known Member
As will anyone, I dare say, who has had a battery fail in-flight!
At that point, your options vanish quickly, and quite possibly your bird as well.
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