Every so often somebody in the forums or youtubes mentions that the 1S batteries in our whoops are subject to more voltage sag than, say, the 3S to 6S flight packs during flight.

In the Betaflight power and battery tab, if you set the battery to the "default" Warn at 3.5 volts and Mininum at 3.3 volts, you will be staring at annoying battery warnings pretty much the whole time.  Even 4.35 LiHV batteries will sag to 3.5 or lower just after takeoff and will get down to 3.3 volts after a few more seconds of flight (BT2.0 goes longer than PH2.0).  When you land the drone and disconnect the 1S battery, it recovers quickly to considerably higher voltage at rest.

This supposedly is quite normal for 1S batteries.

I tried setting my Warn to 3.1 volts and Min to 2.9 volts (as some have suggested), but when it starts warning "Voltage Low" the "Land Now" comes on within seconds, and the drone failsafes right then.

OK, that's too low.

I have now been running the Warn at 3.1 volts and Min at 3.0 volts.  Now the "Voltage Low" warning comes on but I still have about 20 seconds before the "Land Now" comes on, and I can still land safely under power.  Again, when disconnected the battery quickly recovers to about 3.7 volts without damage.

3S to 6S settings should probably be kept at 3.5 and 3.3 volts per cell since they don't sag as much in flight.

These little batteries delivering 12 amps is amazing.

it depends on the battery quality and sort of flight.

i fly 300mah tattus actual and when i drain them down to 2,9v they does recover to 3,8v.
they doesnt provide the power i would like. i doesnt even care about warnings, ignore them, just focus on less than 3v. a drained lipo does tell more by the performancr than by the voltage.

i would suggest to focus on the recovery voltage and experience from there, what landnig voltage you should choose.

drop directly to 3,5v or lower does mean thr quality of your lipos is bad, i would suggest to order some decent tattus 300mah or gnb 300mah batteries, compare them and maybe sort the actual ones out

Quote:Even 4.35 LiHV batteries will sag to 3.5 or lower just after takeoff and will get down to 3.3 volts after a few more seconds of flight (BT2.0 goes longer than PH2.0).  When you land the drone and disconnect the 1S battery, it recovers quickly to considerably higher voltage at rest.

This supposedly is quite normal for 1S batteries.

Yes because the voltage reading you're getting on the OSD whilst flying is when the battery is under considerable load.  We find different ways to combat this load in 1S/whoop rigs, using bt2 (or better) connectors and setting esc pwm to 48kHz are two of the most popular ways.

Fine tuning the voltage min and warning settings is a challenge but worth it as you've found.  On my 1S toothpicks i use 3.3v min and 3.2v warn as these values suit the dynamics of the battery and quad I'm using.

Nice to see someone post about this behavior 

A side measurement is the difference in voltage at load (at end of flight) versus voltage at rest.  If these values are large (>0.5 volts) it would suggest too hot of a motor/battery combo.

I came across this page a few days ago (link below). It lists some "folded cell" or "square cell" 300mAh batteries for PH2.0 or BT2.0 that are supposed to outperform most all the regular little 1S batteries and is supposed to be what the racers are using. I still need to look up what "square" or "folded" cell means. I plan on getting some to see just how good they are...

I will include the video which led me to the page and explains why he chose what he did.

https://www.fpvknowitall.com/fpv-shoppin...iny-whoop/

No, 3.1 and 3.0 are still a bit too low. It does indeed extend the flight time (psychologically at least), but the time delta between Voltage Low and Land Now is still too short, and it failsafes too soon after Land Now.

I will now try 3.2 and 3.1 and will report on it.

You can also use values like 3.25 and 3.13 etc, to fine tune.

This was a really helpful thread for me. I have been getting insanely short 1S flight times because I was living by the general rule of 3.5 warning 3.3 land now. The 1S batteries always bounced back to 4.1 or so, but I was concerned about deeply damaging them if I flew below these limits. I've just adjusted my hdzero mob6 to warn at 3.3 and land at 3.15.
Significantly better flight time and the batteries are bouncing to about 3.8 afterwards, which seems ideal.
Thanks for the info.

Today I flew a half dozen 1S batteries with an Acrobee65 BLV4 (converted to BT2.0) set at Warn=3.2 and Min=3.1.

This worked very well.  When I got the "Voltage Low" warning I still had about 45 seconds of easy flight.  When I got the "Land Now" warning I had about 20 seconds to land.  After about 15 of those 20 seconds the video started to go out.  Good time to land.

When I removed the battery and checked the voltage, it had already recovered to 3.5 volts.  However, as soon as I loaded it again, it failsafed.  This seems to be the normal behavior for LiHV.

This is perfect.

For today's test I used a group of the new square cell folded 1S 300 mAh batteries.  Four of the batteries gave me 3 minutes of flight time in easy flight.  Two of the batteries gave me less than one minute.  I am discharging those two for disposal.

YMMV, of course.

For 2S the settings for battery at Warn=3.3 and Min=3.2 seem to work well.  With a Mobula8 2S I am getting nearly 10 minutes flight time for easy flight.