HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old 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
RobT01 is offline Find More Posts by RobT01
Reply With Quote
Sign up now
to remove ads between posts
Old Sep 17, 2012, 08:13 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
20,849 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.
hoppy is offline Find More Posts by hoppy
Reply With Quote
Old Sep 17, 2012, 10:25 PM
Registered User
United States, NY, Syosset
Joined Jun 2012
81 Posts
Thanks!
RobT01 is offline Find More Posts by RobT01
Reply With Quote
Old Sep 18, 2012, 07:45 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,362 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
solentlife is offline Find More Posts by solentlife
Reply With Quote
Old Sep 23, 2012, 02:40 PM
Destroyer of Balsa
bigoof's Avatar
United States, FL, Port Orange
Joined Aug 2012
27 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?
bigoof is offline Find More Posts by bigoof
Reply With Quote
Old Sep 23, 2012, 02:58 PM
RC Helicopter Pilot
TheWoodCrafter's Avatar
United States, CA, Westminster
Joined Mar 2010
1,696 Posts
Quote:
Originally Posted by bigoof View Post
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.
TheWoodCrafter is offline Find More Posts by TheWoodCrafter
Reply With Quote
Old Sep 23, 2012, 09:25 PM
Registered User
Australia, VIC, Melbourne
Joined Feb 2010
1,691 Posts
Quote:
Originally Posted by solentlife View Post
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.
desertstalker is offline Find More Posts by desertstalker
Reply With Quote
Old Sep 26, 2012, 07:46 PM
Destroyer of Balsa
bigoof's Avatar
United States, FL, Port Orange
Joined Aug 2012
27 Posts
desertstalker, that seems to be a pretty good idea and within my mathmatical ability.
bigoof is offline Find More Posts by bigoof
Reply With Quote
Old Sep 27, 2012, 07:15 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,362 Posts
Quote:
Originally Posted by desertstalker View Post
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
solentlife is offline Find More Posts by solentlife
Reply With Quote
Old 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.
RobT01 is offline Find More Posts by RobT01
Reply With Quote
Old Sep 28, 2012, 03:52 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,362 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
solentlife is offline Find More Posts by solentlife
Reply With Quote
Old Sep 28, 2012, 02:24 PM
Registered User
n808's Avatar
Seattle, WA
Joined Apr 2007
66 Posts
Quote:
Originally Posted by solentlife View Post
..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.
n808 is offline Find More Posts by n808
Reply With Quote
Old Sep 29, 2012, 04:06 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,362 Posts
Quote:
Originally Posted by n808 View Post
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
solentlife is offline Find More Posts by solentlife
Reply With Quote
Old Sep 29, 2012, 10:50 AM
Registered User
n808's Avatar
Seattle, WA
Joined Apr 2007
66 Posts
Quote:
Originally Posted by solentlife View Post
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.
n808 is offline Find More Posts by n808
Reply With Quote
Old Sep 30, 2012, 03:26 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,362 Posts
Quote:
Originally Posted by n808 View Post
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
solentlife is offline Find More Posts by solentlife
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Calculating flying time. seedo Power Systems 6 Apr 25, 2012 05:02 PM
Question calculating fly time saving the lipos A1CpuntacanaDr Batteries and Chargers 13 Apr 12, 2012 02:42 AM
Question Flying Time Calculation nextofkin Batteries and Chargers 6 Mar 10, 2012 01:45 AM
flight time calculation bach939 Batteries and Chargers 3 Oct 06, 2004 08:20 PM