P3A tried to autoland with a battery critical warning.

[peter west nz]

If you upload the flight log from your controller to healthy drones it will show you the battery current under load throughout the flight. The most accurate way to check usable capacity is to monitor mah returned to the pack while charging, the smart board in the battery logs this. You can find it in Healthy drones as last recorded mah.

It does show current, but only shows several ranges of 5A for the current. This makes me think that this is being calculated from the maHr figure, using a lookup table, and is only very approximate. I don't believe that there are any actual current sensors, because of their I2R losses. However, there are other ways to do this with solid state sensors, and one turn of wire. Can you hear me DJI?

 

[With The Birds]

It does show current, but only shows several ranges of 5A for the current. This makes me think that this is being calculated from the maHr figure, using a lookup table, and is only very approximate. I don't believe that there are any actual current sensors, because of their I2R losses. However, there are other ways to do this with solid state sensors, and one turn of wire. Can you hear me DJI?

I strongly expect actual current is being measured, DJI use a Texas Instruments three phase motor driver SOC, it is capable of logging instantaneous drive current with high precision. Whether the info makes it into the log or not is another issue.

 

[peter west nz]

I stand corrected. Of course they are using 3ø drivers. Even though they might use the current reading from that chip to limit dissipation in the escs quite closely, there are probably so many readings per second, that it isn't practical to store more than an average every few seconds, or possibly, those are the min-max spreads

 

[rkingsb353]

After reading the post dealing with possible battery failure I took a look at the 2 batteries that I have used going on 2 years next month.
One has a charge of 144 times with a reading of 3.68v with 20% charge left.At take off the cells readings were 4.5v.
The second battery has been changed 164 times with a reading of 3.67 with about 20% charge left .At take off the cell readings were 4.35.
What are your thoughts with these numbers as to possibly having problems in near future.

 

[peter west nz]

I have taken this to cut off again & I will cycle it once more. My guess it that it will give about 20min next time.
Any bets?

Good job i didn't put any money on it - 17min again. Hd shows it at 85% capacity. however that is one whole lot better than the 1min flight that started all this. And the no 4 cell is working normally. Ok to hover in place for 15 min. Just don't go too far away....