Sep 17, 2012, 07:55 PM Registered User United States, NY, Syosset Joined Jun 2012 81 Posts Discussion Calculating flight time What is the best way to calculate the flight time you should be running a pack? Should you use MAH put back in after recharging or or the voltage the pack comes back after a flight? Does this change when running two packs in series ? (ir two 5 cell packs to act like a 10 cell). Thanks, Rob
 Sep 17, 2012, 08:13 PM Space Coast USA Space Coast Joined Oct 2000 20,719 Posts IMO, as long as the voltage is above 3.7v/cell after landing, flight time is OK. The problem with using the mah put back in is that you have to know the actual pack capacity for that number to be meaningful. As the pack ages, the capacity diminishes. For instance, an old 1000mah pack may have an actual capacity of 800mah. The user puts 800 mah back in thinking he has used only 80% of the capacity when he has really used 100%. The voltage however will still give a good indication of the remaining capacity. Old or new pack, 3.7v/cell will be about 80% discharged.
 Sep 17, 2012, 10:25 PM Registered User United States, NY, Syosset Joined Jun 2012 81 Posts Thanks!
 Sep 18, 2012, 07:45 AM 222 km/hr Parkjet flyer Latvia / UK visits Joined Jan 2010 8,335 Posts For a new pack and model set-up .... Wattmeter and record amps / watts / volts. Then simple maths tells you max time to flat pack ... I then set my time for 75% of that .... I soon know if a pack is getting past its prime ... by watching the charge after such use. Plus usually the model tells you if not powered so well .... Nigel
 Sep 23, 2012, 02:40 PM Just Learning United States, FL, Port Orange Joined Aug 2012 26 Posts Good thread. I have the same question. Should I just make an initial short flight on a new, fully charged battery and read the voltage placed back onto the battery when recharging?
Sep 23, 2012, 02:58 PM
RC Helicopter Pilot
United States, CA, Westminster
Joined Mar 2010
1,696 Posts
Quote:
 Originally Posted by bigoof Good thread. I have the same question. Should I just make an initial short flight on a new, fully charged battery and read the voltage placed back onto the battery when recharging?
I read the mAh put back into the pack and make sure it is 80% or less of the packs total capacity.
Sep 23, 2012, 09:25 PM
Registered User
Australia, VIC, Melbourne
Joined Feb 2010
1,605 Posts
Quote:
 Originally Posted by solentlife For a new pack and model set-up .... Wattmeter and record amps / watts / volts. Then simple maths tells you max time to flat pack ... I then set my time for 75% of that .... I soon know if a pack is getting past its prime ... by watching the charge after such use. Plus usually the model tells you if not powered so well .... Nigel
That assumes you are running flat out all the time?

Seems unlikely for most aircraft.

My method, fly for 3 mins, charge pack, that gives you mAh/min from which you can figure out how long to fly.
 Sep 26, 2012, 07:46 PM Just Learning United States, FL, Port Orange Joined Aug 2012 26 Posts desertstalker, that seems to be a pretty good idea and within my mathmatical ability.
Sep 27, 2012, 07:15 AM
222 km/hr Parkjet flyer
Latvia / UK visits
Joined Jan 2010
8,335 Posts
Quote:
 Originally Posted by desertstalker That assumes you are running flat out all the time? Seems unlikely for most aircraft. My method, fly for 3 mins, charge pack, that gives you mAh/min from which you can figure out how long to fly.
Correct ... which in my book gives me an added safety factor on run-time. Example :

My 50mm T45 has a 4S pack in it ... WOT 75% run time is 2.7 mins on the smaller 1500 pack .... but throttling the model when flying gives me over 3.5mins.

If I was to use the mA put back format ... I would then be setting timer to the HIGHER figure and in my mind risking an LVC .... but with my system with timer set at 2.7 mins - I KNOW I am safe and KNOW I have plenty margin left to go round again for landing if needed.

Second I have 3 models that do not get past 3 mins in the air anyway !! 1 of them is under 2 mins ... my Speed Record Parkjet.

I realise each to their own and I prefer knowing that my packs are still reasonable charge level when landed. I also am a speed freak and tend to scream my EDF / Pushers around at WOT a lot !

Nigel
 Sep 27, 2012, 05:18 PM Registered User United States, NY, Syosset Joined Jun 2012 81 Posts I found this after starting this thread: http://www.rcgroups.com/forums/showp...57&postcount=7 Any reason not to stretch the flight a bit each time until I am above 3.70 volts per cell.
 Sep 28, 2012, 03:52 AM 222 km/hr Parkjet flyer Latvia / UK visits Joined Jan 2010 8,335 Posts There is another factor to be aware of ... we rarely fly same twice .... so if we gauge our flight times on a varied throttle flight and mA put back into pack ... we may run over a sensible limit on a later flight. My use of WOT amp's calc means I will not do that ....... my timer buzzes well before that. Nigel
Sep 28, 2012, 02:24 PM
Registered User
Seattle, WA
Joined Apr 2007
66 Posts
Quote:
 Originally Posted by solentlife ..WOT..
I am such a noob to rcgroups - have been hanging out on runryder and helifreak, so I had to google what WOT means here..

I have been using above mentioned methods, start conservatively, increase until 75-80%. Then I got a 45C battery this summer, all my old ones from two years back are 25C. After breaking it in, and I did a WOT flight, it was able to deliver so much more current, that I had to stop early, noticing a drop in headspeed. The voltage wasn't lower than 3.69 on two cells, except on one, 3.21V, which seems out of the ordinary unbalanced, for a high quality relatively new battery. Reducing flight time for this battery, and when I fly to 3.75V, the "bad" cell goes to 3.70V.
Sep 29, 2012, 04:06 AM
222 km/hr Parkjet flyer
Latvia / UK visits
Joined Jan 2010
8,335 Posts
Quote:
 Originally Posted by n808 I am such a noob to rcgroups - have been hanging out on runryder and helifreak, so I had to google what WOT means here.. I have been using above mentioned methods, start conservatively, increase until 75-80%. Then I got a 45C battery this summer, all my old ones from two years back are 25C. After breaking it in, and I did a WOT flight, it was able to deliver so much more current, that I had to stop early, noticing a drop in headspeed. The voltage wasn't lower than 3.69 on two cells, except on one, 3.21V, which seems out of the ordinary unbalanced, for a high quality relatively new battery. Reducing flight time for this battery, and when I fly to 3.75V, the "bad" cell goes to 3.70V.
Sounds more like "High Price" than High Quality ! Even the real cheap 2 for 1 deals I've had of Ebay have better cell results than that ........
Seems a battery that needs balance charging each time ?

Nigel
Sep 29, 2012, 10:50 AM
Registered User
Seattle, WA
Joined Apr 2007
66 Posts
Quote:
 Originally Posted by solentlife Sounds more like "High Price" than High Quality ! Even the real cheap 2 for 1 deals I've had of Ebay have better cell results than that
I agree, and I sent a photo of the cell voltages and battery to ReadyHeli a few days ago, and they promptly refunded the price (store credit) since they were out of stock (almost always is for this battery). It's still very usable as long as I remember to fly a little shorter. It's a Thor Voltz battery.
Sep 30, 2012, 03:26 AM
222 km/hr Parkjet flyer
Latvia / UK visits
Joined Jan 2010
8,335 Posts
Quote:
 Originally Posted by n808 I agree, and I sent a photo of the cell voltages and battery to ReadyHeli a few days ago, and they promptly refunded the price (store credit) since they were out of stock (almost always is for this battery). It's still very usable as long as I remember to fly a little shorter. It's a Thor Voltz battery.
Nice one ... as you say - you know the problem ... you know the way to use it ...

I have 2 2280mAh 3S packs that arrived puffed of ebay. They have poor power delivery and fly my fixed wings - but with no real go as my usual 3S packs. But they hover my 450 Heli ok . So like you - I know the limitation of the packs and use accordingly.
I was surprised they flew the heli reasonably, considering the lack of go in the fixed wing jobs. I always assumed the heli to be a greater load on them. I cannot do much more than hover though with them. At least it saves my other packs for serious use !!

Nigel