[dingy]

This is a very interesting article that I found some time ago.

Also remember the older a battery becomes the shorter charged time is.

Attached as a file also for reference:-



Calculating Battery Flight time
Ah x 60 / amps pulled
So, Lets see a couple examples
2000mah battery = 2ah
4000mah battery = 4ah
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
2ah x 60 = 120 120/30 = 4 minutes full throttle (slightly less due to servo power draw)
4ah x 60 = 240 240/30 = 8 minutes full throttle
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Battery C rating
This rating is considered the maximum safe (constant amp draw)
1000mah 20c pack = 1ah x 20c = 20amps
2000mah 20c pack = 2ah x 20c = 40amps
4000mah 30c pack = 4ah x 30c = 120amps
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
1ah 20c battery pulling 30amps = 30/1 = 30c (this is above the C rating, this will puff the battery)
2ah 20c battery pulling 30 amps = 30/2 = 15c (this is well below the max constant amp draw… This will
work good)
4ah 30c battery pulling 30amps = 30/4 = 7.5c (this is extremely good at this rate pretty much any halfway
decent cheap battery will give great results)
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Lets see what we get if we re-prop for a higher voltage (not all motors will allow this, but it is usually
good if it will)
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
Volts x amps = watts (volts times amps equals watts)
11.1v x 30a = 333watts
Now Lets use a 480 size motor on 4cell as an example… we reverse the numbers to give us the samw watts
with less amps (less amps = less heat
333 / 14.8 = 22.5amps
So if we look at a standard 480 motor we can see that we’ll get the same power with 22.5amps instead of
30amps on 3cell…. (You will prop down in size to do this)
A bit “o” confusion on battery size on changing voltage Why do people think that you’ll be heavier
with a 4cell than a 3cell , simply because they aren’t using a smaller capacity battery with the same
weight
Using the above info above we will look at a few options on batterys….
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
A standard 480 outrunner is propped around 22.5 amps on a 4cell battery
Lets start with a 2200mah battery on 3cell
(average weight of a cheap 2200mah 3cell pack is around 200grams)
2.2ah x 60 = 132 / 30 = 4.4 minutes full throttle flight time
(average weight of a cheap 1700mah 4cell pack is around 200grams)
1.7ah x 60 = 102 / 22.5 = 4.5 minutes full throttle flight time
So, what we have learned is that you can get the same power (333watts) out of the same (or less) weight
battey, and Pull less amps (less heat)
We must be carefull to realize though that all motors cannot just be re-proped for a higher voltage due to
motor deign or materials used in the design... and at all times you should use a good wattmeter to
determine all factors involved


Regards,

Dingy