Cell Deviation and Charging

[NoVaMavicPilot]

Hi All,

I am a M2P pilot with about 80 safe flights under my belt since getting my commercial cert. I have my batteries set to discharge at 2 days and never let them sit fully charged. I have had to "top off" a few times when I knew they were discharging to 90 percent or so. I always land with no less than about 35-40 percent battery, to be safe. I have three batteries and charge in sequence on a DJI multi-charger. No flying in extreme conditions, although today, here near D.C. I flew in 20 degrees to actually test battery performance straight above my house. My batteries have all been charged less than 24 times. Towards the end of my flight I got a lost connection notice, but the M2P was fully responsive (for another discussion thread). Of greater concern is one my batteries showing a growing number of cell deviations per flight. I've checks the discussions, and it seems there are various opinions on how concerning this could be, but I am wondering if I should try to "reset" these batteries by bringing them down really low and recharging? Is there a battery optimization procedure you recommend beyond just letting it self-discharge? Also, does the self-discharge mode get it down to the optimal storage percentage or is there a better procedure? I love this forum. Thanks!

 

[NoVaMavicPilot]

Hi All,

I am a M2P pilot with about 80 safe flights under my belt since getting my commercial cert. I have my batteries set to discharge at 2 days and never let them sit fully charged. I have had to "top off" a few times when I knew they were discharging to 90 percent or so. I always land with no less than about 35-40 percent battery, to be safe. I have three batteries and charge in sequence on a DJI multi-charger. No flying in extreme conditions, although today, here near D.C. I flew in 20 degrees to actually test battery performance straight above my house. My batteries have all been charged less than 24 times. Towards the end of my flight I got a lost connection notice, but the M2P was fully responsive (for another discussion thread). Of greater concern is one my batteries showing a growing number of cell deviations per flight. I've checks the discussions, and it seems there are various opinions on how concerning this could be, but I am wondering if I should try to "reset" these batteries by bringing them down really low and recharging? Is there a battery optimization procedure you recommend beyond just letting it self-discharge? Also, does the self-discharge mode get it down to the optimal storage percentage or is there a better procedure? I love this forum. Thanks!

 

[old man mavic]

its better not to just rely on the self discharge part of the BMS
fly them down to 40% and they will be good to store for some considerable time
the BMS actually does the cell balancing part at the end of the charging cycle so make sure that you dont disconnect the charger till the lights have gone off indicating a full charge
not all the mavics have the same indication at full charge some of them are fully charged when all the lights are on and not flashing
its quite normal for slight cell deviations to take place during flight depending on the load placed on the battery
airdata recommend doing the deep discharge scenario at set intervals
but DJI have stopped recommending it now ,but if you feel it would help with your battery issue ,then of course give it a try with the one battery you are seeing the issue with

 

[Ralph thompson]

deviations seem normal, I often get big differences between cell 4 and others. It tends to happen under load like rapid climb and in -24deg c I got a really big difference last Friday. I have found that discharging to 0 ( until the smart battery shuts off) makes a big difference, usually fixing the problem. I wait til the end of the day when my iPad is fairly discharged and plug it into the smart battery using the DJI adapter. once plugged in then don’t forget to turn the smart battery on. From 30% it will completely discharge before the iPad is charged and will switch off. Make sure it’s cooled, then you must fully charge it. Should fix the problem provided battery is in good shape, no swelling or cracks.

 

[NoVaMavicPilot]

Thanks. It seems like this is a common fear, unnecessarily caused by paying close attention to granular Air Data. I will try deep discharges and see if there's any improvement.

 

[Ralph thompson]

It isn’t just a fear, it is a real problem because I believe if the cells differences get too big, the control mechanism can interpret this as a fully depleted battery and shut down. Others have more knowledge of smart battery issues but I have heard of this deviation causing major problems.