Battery life depleting after several flights

Hello everyone! Well, I have been having some issues with flight time on a F450 Alien frame quadcopter build. Recently I picked up a Zeee 11.1V 7200mAh 80C 3S Lipo Battery and was getting around 11 to 12 minutes roughly of flight time. After about 4 or so flights, I am down to about 7 mintues of flight. This is a pretty large reduction in just several flights, and the initial voltage drop on this most recent flight was larger than ever before at almost 2v.

F450 Alienframe
20A BLHeli ESC
APM 2.8 (running 3.2.1) {I know its super old and am currently in the stages of upgrading to the cube :grinning:}
Emax 2213/935kv using 1045 propellers (ABS)
Total weight is roughly 1775 grams and its a tad bit tail heavy (due to the large battery)

My question is, is this a bad battery / brand or is there another factor going on here? It also feels as if the motors are getting too hot, not too hot to touch though.

I’ve attached a link to the latest flight datalog below containing the .bin and .log files.

It seems like something is making motor consume more power. Can you test the amp draw of your setup with current battery at cruising throttle and calculate flight time accordingly. If it matches with actual flight time then there is no issue with the battery. If it doesn’t match approximately then there is something wrong with the battery.
Also check the voltage after charging the battery.
Check if your charger is in storage mode or charge mode.

APM 2.8…,
firmware 3.2.1…,
with that motors & frame & setup…,
I don’t think you will get much help…,
READ , Read, read…
& try with a 2200mah battery…,
AUW…?..(max). … below…1.2Kg:

The vehicle weight without battery is roughly 1.3kg and we were using the 4000mAh 20c venom batteries before moving up to 7200. With the 4000 we would only get maybe 4-5 minutes of flight, not even enough to get it to autotune fully. The charger being used is the imax b6 balance charger, using the setting “balance charge” at 4A (not storage). This last flight, I charged the battery back up and it put about 3003mAh back in. Mp has it at 3200mAh and some change when I graph the curTot from datalogs. I will run a hover test today with the power Analyzer and see if the power draw matches MP.

1 Like

According to eclac I should have a 1.9155:1 ratio of thrust which is just shy of 2:1 (pretty standard). It is also saying I should be seeing 14 minute flight times. Internal resistance on the battery is barely 2, 1, 1 ohms so I dont think it’s bad just yet (maybe poor quality).

Bad battery.
Look at the voltage drop when you power up - it b basically hits your FS immediately.
Maybe a really old battery.
I have some that have gotten this soft, fully charged and balanced and 3 to 4 minutes flight time.
For an 80C (500A ???) rating a 2v drop is no good.
You will be lucky to get 5C from it.

The total current put back in tells the story, and CurrTot, you are getting less than half the mAh from the battery at 3.5C before your voltage gets too low for safety.

1 Like

Thank you for your time. I was also suspecting a bad battery as well due to the large voltage drop (however the internal resistance for each cell is very low). The only thing that strikes me as odd is, this is not an old battery. In fact, I ordered this less than a month ago (who knows how long its been sitting in the warehouse and in what conditions). The flight just before this log (08-30, link posted below to .log and .bin) I had just over 11 minutes of flight (same battery). I’ve had a total of maybe 5 flights on this battery. I go from 11 minutes of flight (3rd flight) down to 7 minutes (4th flight). This morning I’ve tested the battery again and got even less flight time at maybe just over 5 minutes (battery still at 60%), link posted below as 09-04.