Lipo's and warning voltages.

[ChrisH]

Hi All,

I';ve been thinking - a rare occurrence - as I am fine tuning the various gains and warnings on a Naza/F450 combo. Now, the thought process. For different sized Lipo batteries the power graph for discharge/time should look similar except that for a larger capacity the time axis would be longer. Therefore, if you are setting the alarm voltages in the assistant, would I be correct in assuming that for a higher capacity battery (5000 3S) you could set the warning voltage a point or two lower than for a smaller (2200 3S) battery. This is assuming that you RTH when the lower limit is reached and the main aim is to land before the critical 3.3V/cell barrier? This is based on my limited understanding of Lipos and that the larger capacity would (should) take longer to drop to the critical level.

I would appreciate a view on this or am I making m head hurt without a purpose?

Hoping for some flying weather this weekend. 

Cheers.

[Ross]

Must admit..never thought of that..but.
Depends how you fly.
I would think    lower capacity battery flown slowly, no fancy stuff  may last longer than a higher capacity flown at high speed and with aeros thrown in......Think  car..driven  fast..driven slower...and result in MPG.
(Well..that';s how I  see it )

[ChrisH]

Hi Ross,

Agree with that about life versus driving/flying style! I was thinking of the discharge graph from different sized Lipo';s assuming other factors remained the same.

It';s just I had a thought that the warning voltage may be knocking useful flying time off a battery because it cannot compensate for capacity, only voltage and warns too early.

Cheers, 

[Ross]

Better safe than sorry!    

[sendtohim]

Better safe than sorry!    

i 2nd that if you let them drop to 3.4-3.5v you will notice a power drop and it will not get you out of trouble if you need it

better to be safe than sorry just for a extra 30 secs of flight in some cases

[guest325]

With my 450 (RCTimer Flamewheel clone) I get about 8 mins of mixed flying from a 2200 mah 3S battery but set my timer to 7 mins, I never like my batteries to drop below 30%!
If you are using a 5000mah then you should get approx 5000/2200x7 mins flying - but personally I would land and use my battery checker a good minute earlier, also remember you get less flight time when it';s cold.

[ChrisH]

Thanks Guys for all the thoughts. It wasn';t about pushing the batteries beyond limits, it was more to do with the theory of the decay of a larger battery compared to a smaller one!

I think I';ll hook up the voltage monitor on the AR8000 Rx then I can see in real time!! See what I feel like tomorrow. Got gains to modify then test. Also modifying the GoPro mount to get rid of a bit of jello. See how it goes.

Cheers all and keep the ideas flowing!