I do not absolutely know if my battery mismanagement was the cause of the crash or even contributed to the crash.
Basically, I left the batteries on the charger all the time. I *assumed* the batteries were at full charge when removed. I do not know if these lithium batteries have any memory or over charge protection circuits.
I would not leave the batteries on the charger. Once a battery charging cycle is finished the battery turns itself off. It will keep a 95%-100% charge for a maximum of 10 days (6 days is default). This can be programmed for each battery pack individually through the Autel Explorer App. Mine are all set to allow 10 days. After 10 days the charge will automatically be reduced to 60% for fire safety. Then the day before a flight I recharge them to full again.
So keep in mind, when the software indicators show a range of 100% down to 0%, this in reality reflects the cells in the battery pack having a range from about 4.3 V. down to 3.0 V, and this multiplied by the number of cells in one pack gives us a usable output of about 7100 mHa at 9-13 Volts for the
Evo 2.
Apart from only (re)charging the last bit from 60% to 100% a day before using them, also temperature conditions on the day of flight will affect the real output. This is why Autel advises us all to store and use LiPo batteries at room temperature like a good bottle of red wine ;-)
Then battery packs with multiple cells showing big differences in the charge for each cell should not be used for flight. If one cell is not in order it will drain the other cells and screw up the remaining flight time prediction. Drain that battery by hovering close to the ground, then recharge it. If the large difference between cells persists, buy a new battery and dispose of the faulty one.
A search online with the search engine starting with a G, Tells us "Overcharging your battery and letting it run empty are poor practices that will lead to the premature deterioration of your LiPo battery. Never leave it charging once it has reached the 4.2 V full capacity, and don't let it drain to below 3.0 V."
See Battery Management Panel in the Explorer App looks like this: image.png
Moreover, when a LiPo battery pack was left unused for a while, don't forget to check its charge level once every month. You don't need to use the App for this, just press the button on the battery. Some of my battery packs were were produced in the year 2020 and some in 2021. Those four battery packs were all charged to 100% on the same day and about a month and a half later without being used only A and D seem to have lost some charge to a level below 50%, the other two B and C are still showing about 60% of charge. They were all kept in the same place. So it's time for me to top up A and D to keep them healthy. This also tells me their absolute age is not as important, each LiPo cell just behaves slightly different over time. Because pack A had the most flight time and D was only used for flight once. Still D being younger and used less is not performing as good as their counter parts B and C.
