Hi. Just the other day, I noticed on my Airdata that my Phantom 4 Standard No1 battery of three, which has been recharged 65 times, is exhibiting cell deviations in Cell 4 which exceed the norm.I flew a 5 minute waypoint mission with no dramas, but the data is worrying. The battery still shows as 94% efficient, but the cell variation is of concern.  My two other batteries have no excessive deviations. All have been well cared for, and deep-discharged periodically as recommended .  Maybe it's time to retire this one?  Any observations or shared experience would help. TIA.

Personally, I'd make an attempt to balance it with a deep discharge.  

Otherwise, I'd semi-retire it (only use it for short flights) - and land it at 50% or so...

MHO

If the deviation is consistent throughout the flight, as appears to be the case from the short amount of data above then that cell has the same capacity as the others, it is just out of balance for some reason, maybe through lack of use.

So a discharge down to 8%, charge to 100%, leave it for a day and then attempt to charge to 100% again (might have to turn the battery on before it will restart charging), then check to see how it behaves over a few flights.  Give it plenty of use for a while if it appears to be OK, and don't take it down to critical voltage if it doesn't appear OK.

Mark The Droner Posted at 2018-6-19 07:52
Personally, I'd make an attempt to balance it with a deep discharge.  

Otherwise, I'd semi-retire it (only use it for short flights) - and land it at 50% or so...

I shall try that in the first instance. The last deep discharge on that battery was only fifteen or so cycles ago, and I use all the batteries on average once a week, rotating them in turn.  I'd like to think there's a bit more reliable life left in this one yet, but short flights might be a worthwhile constraint. Thanks.

Nigel_ Posted at 2018-6-19 08:18
If the deviation is consistent throughout the flight, as appears to be the case from the short amount of data above then that cell has the same capacity as the others, it is just out of balance for some reason, maybe through lack of use.

So a discharge down to 8%, charge to 100%, leave it for a day and then attempt to charge to 100% again (might have to turn the battery on before it will restart charging), then check to see how it behaves over a few flights.  Give it plenty of use for a while if it appears to be OK, and don't take it down to critical voltage if it doesn't appear OK.

Yes, throughout the whole flight that one cell was consistently  0.08 to 0.09v down on the other three.
I've had an eye on this battery for a week or two, as I first noticed this behaviour back then, but have since had one other flight where the battery showed no problem. I gave it a rare outing in Sport mode around the neighbouring field to see how it performed. Just this morning, when flying a short waypoint mission, it's back to the red line.  I shall deep-discharge it as you suggest and recharge it, then see what happens.
I'll report back in a few days. Thanks.

Nigel_ Posted at 2018-6-19 08:18
If the deviation is consistent throughout the flight, as appears to be the case from the short amount of data above then that cell has the same capacity as the others, it is just out of balance for some reason, maybe through lack of use.

So a discharge down to 8%, charge to 100%, leave it for a day and then attempt to charge to 100% again (might have to turn the battery on before it will restart charging), then check to see how it behaves over a few flights.  Give it plenty of use for a while if it appears to be OK, and don't take it down to critical voltage if it doesn't appear OK.

OK. Deep discharge to 8% effected. Battery left to cool to ambient for a couple of hours, then fully charged. After a couple of days at room temperature, I flew the Phantom again with it this morning, after  checking that charge was still at 100% and the battery would not accept any more charge.
A fifteen minute flight back and forth across the fields in all directions, changing height, yaw, direction, reverse and even a bit of thrash in sport mode achieving 85Kph with following wind. The drone performed faultlessly.  The data from the flight, however, indicates that throughout, cell No4 was consistently 0.08v down on the others. Starting with 100% battery, I flew it down to 38% before landing.
I don't think this battery has reached end-of-life just yet, but I'll be relegating it to the "B" team and only using it for shorter flights.

Blériot53 Posted at 2018-6-24 23:45
OK. Deep discharge to 8% effected. Battery left to cool to ambient for a couple of hours, then fully charged. After a couple of days at room temperature, I flew the Phantom again with it this morning, after  checking that charge was still at 100% and the battery would not accept any more charge.
A fifteen minute flight back and forth across the fields in all directions, changing height, yaw, direction, reverse and even a bit of thrash in sport mode achieving 85Kph with following wind. The drone performed faultlessly.  The data from the flight, however, indicates that throughout, cell No4 was consistently 0.08v down on the others. Starting with 100% battery, I flew it down to 38% before landing.
I don't think this battery has reached end-of-life just yet, but I'll be relegating it to the "B" team and only using it for shorter flights.

I note the instructions in the manual actually say "less than 8%", i.e. stop at 7%. However I doubt that would make a difference to the balancing.

I think I would use that one in preference to the others, a bit of heavy use might bring it back into balance, however put a mark on it to remind you to land a little early and not at 10%.  I wouldn't be concerned about using it.

The question is, why is it not rebalancing itself?  But as long as it is only a little out then it's not a problem.

I would do as the manual say (page 33) and take it all the way down.
"checking that charge was still at 100% and the battery would not accept any more charge"
From this it is unclear if you did as Nigel said in #3, to top up a near full battery, power the bat on and then connect the charger, it would then take a charge for 10 min+ if any discharge has been going on.

KedDK Posted at 2018-6-25 06:31
I would do as the manual say (page 33) and take it all the way down.
"checking that charge was still at 100% and the battery would not accept any more charge"
From this it is unclear if you did as Nigel said in #3, to top up a near full battery, power the bat on and then connect the charger, it would then take a charge for 10 min+ if any discharge has been going on.

Yes, the battery had retained 100% charge for two days.

Blériot53 Posted at 2018-6-25 08:12
Yes, the battery had retained 100% charge for two days.

That sound alright, just wasn't sure you were aware that powering on the battery before connecting the charger does make a difference on a (close to) full charged battery.

KedDK Posted at 2018-6-26 00:38
That sound alright, just wasn't sure you were aware that powering on the battery before connecting the charger does make a difference on a (close to) full charged battery.

After a recharge last night, I did another flight with the same dubious battery - and this time the results were fine!   The same cell (No4) showed some anomalies, but not outside the criteria for good performance.

Give it a bit more use and it may balance up properly

Nigel_ Posted at 2018-6-28 09:37
Give it a bit more use and it may balance up properly

Maybe it hasn't quite reached retirement age just yet

Blériot53 Posted at 2018-6-28 07:54
After a recharge last night, I did another flight with the same dubious battery - and this time the results were fine!   The same cell (No4) showed some anomalies, but not outside the criteria for good performance.[view_image]

Not sure how to read those gauges, looking almost identical to first post to me beside cell 4 has changed from 54.1 to 56.1 and it say lower is better. But if you see it has improved it sounds good.
Did you ever take it all the way down 7-0% (<8%) as the manual say?

KedDK Posted at 2018-6-28 20:20
Not sure how to read those gauges, looking almost identical to first post to me beside cell 4 has changed from 54.1 to 56.1 and it say lower is better. But if you see it has improved it is sounds good.
Did you ever take it all the way down 7-0% (

When I switched off the drone, after deep discharging the battery , the reading was 7%

Blériot53 Posted at 2018-6-28 22:06
When I switched off the drone, after deep discharging the battery , the reading was 7%

That would be as the manual say then, hopefully it would balance out after some further usage.

I usually aim for the 5% mark doing the deep discharge but has been all the way to 0% one time, i has not noticed any issues but has not studied it as close as the above data show.
After all that percent figure is a strange measurement being some virtual figure, it would be the voltage that count.

Happy flying.