Flight time.

[Jonathan]

Hi I will be flying my 48" ben buckle diamond demon weight around 1.5 lbs using a overlander 2826/18 1000kv v3 motor,  a 1300mAh 2s 7.4v lipo battery pack,  2 mini servos. I probably will fly for around 4 minutes at a time,  how much battery life/duration should I expected,  is there a rule of thumb guide for electric flying. Cheers in advance. 

[Shaun Walsh]

11 minutes ago, Jonathan said:

Hi I will be flying my 48" ben buckle diamond demon weight around 1.5 lbs using a overlander 2826/18 1000kv v3 motor,  a 1300mAh 2s 7.4v lipo battery pack,  2 mini servos. I probably will fly for around 4 minutes at a time,  how much battery life/duration should I expected,  is there a rule of thumb guide for electric flying. Cheers in advance. 

Prop size?

[Jonathan]

Sorry,  9 x 4.5 suggested by the model shop 

[Andy Gates]

From my experience, the easiest way to gauge battery usage is to test the battery after flight using a separate tester which plugs into the Lipo's balance cable.

 

You want to have an indicated 20% left after the battery has rested for a short while.

 

Adjust your flight times accordingly, colder weather will have shortened times, warmer weather longer times.

[Shaun Walsh]

According to propCalc, you should get 10 to 12 minutes of mixed flying but you should fly for a few minutes, land and check the battery for a more accurate estimate.

Also, that set up appears to produce about 30 to 40 watts of power which isn't much for the size and weight of model. A 10 by 5 might be better but you would need to check the current with a wattmeter, also it would reduce the flight time to 8 to 10 minutes.

[Jonathan]

Could anyone suggest the type of battery tester I would need to get please 

[Lipo Man]

7 minutes ago, Jonathan said:

Could anyone suggest the type of battery tester I would need to get please 

Everyone at our club uses one of these:

https://www.amazon.co.uk/Digital-Battery-Capacity-Controller-Batteries/dp/B0C2TYRVZ1/ref=asc_df_B0C2TYRVZ1/?tag=googshopuk-21&linkCode=df0&hvadid=676227278064&hvpos=&hvnetw=g&hvrand=7495944667474387272&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1006534&hvtargid=pla-2265048467684&psc=1&mcid=c9820f8beda83f078ac27674ff206e44&gad_source=1

[Shaun Walsh]

16 minutes ago, Jonathan said:

Could anyone suggest the type of battery tester I would need to get please 

You will also need a watt meter to check the current draw if you experiment with different prop sizes.

[Jonathan]

Fantastic thank you 

[Jonathan]

Evening Lipo Man, thank you for the heads up on the battery capacity checker , got one , brilliant,  once I start flying I will use it most definitely. 

[Chris Walby]

IMO There is no rule of thumb as its totally dependent on the the way you fly or more importantly how you use the throttle stick!

 

Perhaps flow up to 10 minutes with very gentle throttle stick use or...just leave it WOT plus prop hang it and it might be at low voltage cut off on the ESC in 3 minutes.

 

Set the timer for 3 min, land after the time has gone off and then measure the battery voltage/capacity. Then ease the timer out so you normally land with approx 35% that way if you have to go a go around or two you should not be be below 25% (IMHO anything below that reduces the life of the battery long term).

 

Other opinions will be as relevant as mine. 🙂 

[Simon Chaddock]

When you start out with electric limited flight time seems to be a constant problem.

As you progress with more capable planes with a longer potential duration you find what you want to do in the course of the flight is more important than the maximum possible flight time.

I suffered from exactly the "duration" problem when I started out in electric where 3 minutes was likely the best flight time for a simple plane.

My interest in structures and aerodynamics prompted me to do something about it. Improvement in wing aerodynamic efficiency and weight reduction more than doubled the duration of the same basic plane to 8 minutes, mostly due to the reduced throttle required to simply stay up. The full power duration was little changed.

I carried on with this theme with several versions of an improved lighter airframe, more efficient motor and prop with of course a bigger battery.

Although keeping to the same span as the original plane a cruise duration of an hour was achieved then a theoretical 2 hours and finally this plane which has a potential "power on" cruise duration of nearly 4 hours. It has a 1200mm (47") span and it weighs 436g (15.4oz) with a 3800mAh 2s. 

Its maximum duration was never tested as after 2 hours on a flat site I gave up from boredom and a stiff neck.

Maybe it ended up to be a rather pointless exercise however I do still fly it on calmer days safe in the knowledge that the one thing I do not have to worry about is how long it has been in the air.😉

     

Edited April 10 by Simon Chaddock

[Jonathan]

Thanks for the replies really appreciated.  My flying style has always been nice and slow pottering around the sky, my reaction time even when I was young has been slow 😄 The plane I'm building now ben buckle diamond demon I built and flew back in 1993, nice and gentle flying with the mills .75 engine about 3 minutes flight time with the standard tank just enough for me. I've purchased a spare battery so will hopefully be able to have a couple of flights per session.