Bad battery warning, need help

[Google test pilot]

Have been getting Bad Battery warning on past flights, mostly intermittent. Flew today for functional flight to gather battery data within 10' AGL over soft landing area for entire time. Had Bad Battery warning on takeoff . No defects in aircraft or battery performance noted. Below are charts from latest flight today.
http://i1282.photobucket.com/albums/a534/kns1313/Minutes per battery 3 5-29-17.jpg
http://i1282.photobucket.com/albums/a534/kns1313/Battery deviations 3 5-29-17.jpg
http://i1282.photobucket.com/albums/a534/kns1313/Battery health 3 5-29-17.jpg

Yes, something is wrong.
Yes, shouldn't fly.
Battery was drained to 8% prior to flight today, no more than a few days ago and don't recall any flights between now and then.
Can/should it be recharged and "used until destruction"?
How safe is recharging? I've seen lithium battery fires intentionally started during other testing, don't need the mini-rocket in my house.
Will eventual battery failure be instantaneous, i.e. all four motors stop and aircraft becomes a rock, or I continue pushing sticks further and further until reaching a travel limit and no more power can be delivered. at which point I command a controlled landing?

What I'm really after is "What are the charts telling me?" I need an intelligent interpretation as a learning moment so in the future I can interpret these on my own and make more informed decisions. Any help greatly appreciated.

 

[With The Birds]

A link to the flight log would prove significantly more useful than those screenshots you posted. From what you have shared the significantly reduced capacity and high number of major cell voltage deviations suggest this pack is damaged beyond repair. How old is it? How many cycles? Have you consistently flown it out to close to empty, kept it at full charge for extended periods and/or stored it at or close to min charge? This is typical of a battery that has been amused/neglected.

 

[Google test pilot]

1. It was manufactured Aug 2016.
2. It has been charged 38 times.
3. I land it at no less than 20%, usually 25%.
4. Max temp recorded is 138 degrees F.
5. Periodic maintenance rigorously adhered to per Airdata UAV.
6. Normally stored at 20%. It only stores lower than this if I am draining to 8% for the PM. (It may store like this for up to 7 days. Problem cause?)

I need to trust the equipment, so I don't "amuse" it (see above). (I'm not that entertaining from a battery's perspective!) I do not intentionally overstress the system in any way, i.e. fly max speed, request max climb, yank and bank for the heck of it, etc. However, my ignorance is periodically bottomless, so if I'm doing something wrong, it isn't intentional. BTW, the last flight was done at 10' AGL, gentle maneuvering, just to test the battery. Tried to upload the file in .xlsx and .csv format but this thread rejects it.

 

[Robert Smith jr]

I recently had a new battery go bad after approx 5 charge cycles, bad cell. I returned it to DJI for a replacement. You could try contacting support, my other battery's have between 40-60 charge cycles.

 

[With The Birds]

I trust you might have ascertained without any undue effort that "amused" in my response was as a result of predictive text input.

With respect to your points 1 to 4 age and stated typical max flight temps and depletion level at fight end suggest this pack should be healthy at such a low cycle count.

There are other factors at play here, either a cell defect at manufacture and/or less than optimum storage and handling. You give some clues suggesting the later may be applicable.

There is no necessity to perform the discharge to 8% ritual. In fact DJI no longer recommends this practice. The best you might hope for in performing this procedure is a more accurate depiction of actual battery capacity and charge percentage. Arguably you are just putting additional charge cycles on the pack for no good reason.

As to storing below 20%, or more critically 8%, there is a good chance this has contributed to your problems. Best practice is to part charge packs after use aiming for a storage level between 30 and 50%.

Rather than attempting to upload your actual flight log you could have shared a link to the healthydrones log of interest.