Hi,

Although this isn't a DJI flaw in any way, shape or form, I recently became aware of a characteristic of the DJI Mini 2's intelligent flight battery behavior that owners should be fully aware of.   In flight, there is NO battery over-discharge protection function with the Mini 2 drone.  LiPo batteries can be permanently damaged from over-discharge during use and it's very important that drone owners remain cognizant of this at all times during a flight in order to protect the battery from damage.   The DJI Mini 2's intelligent battery DOES provide over-discharge protection (via automatic Hibernation mode) but ONLY when the drone is NOT airborne.   


Ideally, you should be on the ground and finished with your flight with at least a 10 percent indicated charge remaining on the battery, and flights should be planned out accordingly.  If you are regularly ending your drone flights with the "Critically Low Battery" warning, it's not good for your battery's life.   Today I was returning to home with a 10 knot direct headwind from a distance of about 3/4 of a mile.   I had approximately 28 percent charge left on the battery and assumed I would be back on the ground at the launch site with plenty of battery charge remaining.   I returned home at the same altitude I was photographing at (400 ft AGL) which, considering the 10kt direct headwind at that level, was not smart.  I did make it back safely to land with a critical battery level of 3 percent remaining when all was said and done, however discharging a LiPo to this level can really harm it and very significantly shorten it's lifespan.  


It's perfectly understandable that DJI designed the Intelligent Battery to be biased towards the drone's safety in flight rather than that of the protecting the battery.   Drones are much more expensive to replace.  ;)    The DJI Mini 2's owner's manual clearly describes intelligent battery behavior in this regard but drone owners like myself who have RC aircraft experience might have missed this point.   All of the fixed-wing RC aircraft I fly have electronic speed controllers that are programmed to keep the LiPo battery from over-discharging in flight, and will electronically decrease power output to the motor before the LiPo battery drains to below a minimum voltage in order to protect it.   The aforementioned RC ESC's will essentially automatically shut off all power to the propellor motor if you don't land the aircraft in a timely fashion before the battery drains to a critical level.   This behavior, although battery-friendly, could be disastrous for drone pilots for obvious reasons.

I just thought I would point this out as I wasn't clear on the Mini 2's battery behavior until now.   

Hello there Semperator. Good day and thank you for sharing these information and your valued insights with regards to this matter. Great information and thank you for your valued support.

Hi,

In short ; Happy that Mini2 battery in flight is not protected so the remote pilot is in charge to protect bad batt usage
But in case of flight plan miscalculation Mini2 batt will deliver power till the very last juice is used...at 0% indicated level in the FlyApp.

cheers
JJB

As i saw by checking the voltage in the FlyApp for each cell, it was not below the critcal point of 2.8 V at nearly 0%.  
For me the percentage rate as shown in the FlyApp reflects the secure usage frame between 2.8 V and 4.2 V of Lipo batteries.
That the batteries go into hibernation mode is an additional security feature of the intelligent batteries, so that the intelligent battery cicuit will not drain the Lipo cells further more on longtime storage to avoid any harm to the Lipo.
So no worries on that.
But if you go below 0%  for a longer time as shown in some long distance flights on youtube this will definately damage the batteries.

MySky Posted at 3-2 04:24
As i saw by checking the voltage in the FlyApp for each cell, it was not below the critcal point of 2.8 V at nearly 0%.  
For me the percentage rate as shown in the FlyApp reflects the secure usage frame between 2.8 V and 4.2 V of Lipo batteries.
That the batteries go into hibernation mode is an additional security feature of the intelligent batteries, so that the intelligent battery cicuit will not drain the Lipo cells further more on longtime storage to avoid any harm to the Lipo.

I hadn't realized this.   Does DJI publish the critical low voltage specs on the Mini 2 LiPos?   It's certainly possible that DJI factored in a 'buffer' in the percentile battery charge telemetry metric whereas absolute zero percentile represents the equivalent critical minimum voltage rather than a zero voltage condition.  If so, this would actually be wonderful.  

My concern in preserving battery health is less for economical reasons than for safety - if one is flying their drone over water, over a densely developed urban area, etc., it's obviously important that battery performance be both reliable and predictable at all times.   


EDIT:

Most of the literature I've researched specifies 3.0v as the critical minimum voltage for most LiPo battery cells.    The chart here LiPo Battery Depletion Chart indicates that at a zero percent charge, a 2 cell LiPo battery (the Mini 2's configuration) would normally be at 6.55 total volts (counting both cells together), and thus still above the critical mark.   I need to run some tests with my Mini 2 and see at what point the battery cells are reaching 3.0v and how that meshes with the percentile battery charge readout.   

Semperator Posted at 3-2 07:42
I hadn't realized this.   Does DJI publish the critical low voltage specs on the Mini 2 LiPos?   It's certainly possible that DJI factored in a 'buffer' in the percentile battery charge telemetry metric whereas absolute zero percentile represents the equivalent critical minimum voltage rather than a zero voltage condition.  If so, this would actually be wonderful.  

My concern in preserving battery health is less for economical reasons than for safety - if one is flying their drone over water, over a densely developed urban area, etc., it's obviously important that battery performance be both reliable and predictable at all times.   

As Lipo cells will not drain exactly the same, because there is always a drift of some miliivolts., means that one cell can be at 3.0 V and one of the others can be already at 2.8 V.
This drift can increase the older a lipo battery is. This is why it is commenly said that it should, for safety reasons, not drop below 3.1 V as around this point the battery looses drastically its performance and might start to swell and be damaged at  2.8 V.