Swift battery voltage questions.

[Greybird]

My Swift has only been flown on 4S .. 1800rpm at liftoff. Z30-1100 with an 11 tooth pinion. If I go to 5S 5000 with a 10 tooth at 1800, or 6S 5000 with a 9 tooth at 1800, Will I get more flight time with higher voltage? (4S-6S)From my notes, my Swift uses about 533 mah per minute on 4S. Will that decrease with higher voltage, everything else being the same?

[Heritic]

Power (Watts) = Voltage (V) x Current (A).

Thus the theoretical power available if your 4S was 5000mA =

5000mA x 14.8V = 74000 Watts

5000mA x 18.0V = 9000 watts

Thus you have gained 21 1/2% (> 1/5th )more theoretical energy at the same head speed BUT with the extra weight of the 5th cell.

This is all things being equall i.e. cell manufacture.
Heritic

[Heritic]

Power (Watts) = Voltage (V) x Current (A).

Thus the theoretical power available if your 4S was 5000mA =

5000mA x 14.8V = 74000 Watts

5000mA x 18.0V = 9000 watts

Thus you have gained 21 1/2% (> 1/5th )more theoretical energy at the same head speed BUT with the extra weight of the 5th cell.

This is all things being equall i.e. cell manufacture and blade pitch the same.

Thus you can use the extra for more duration or more head speed/load or a little of both
Heritic

[Greybird]

So, everything being equal(ignoring weight), a 6S 5000 pack would fly 43% longer than a 4S 5000 pack?

[Spidious]

According to my test so far a 6S 4900. I can fly 13 minutes at 1700-1800 rpm with a 9t pinion .
But I land at 10 just to be save. And have usually used 58% of the battery

[Heritic]

Power (watts) = Current x Voltage
Thus with 50004S you have 74000Watts potential
50005S you have 9000 Watts potential.

You have gained ALL things being equal 21% more energy at just the extra weight penalty of the 5th cell (if same cell type).
So yo can have approx 1/5 more duration or 1/5 more power/energl (increased head speed) OR a bit of both.
Heritic

[swatson144]

Power (watts) = Current x Voltage
Thus with 50004S you have 74000Watts potential
50005S you have 9000 Watts potential.


Errr mili watts. I wish 74000 watts! 5000mAH = 5 AH
Not to pick nitts but in some later calcs it makes a difference.

You can guess your duration by taking what you have (watts / min) and making a ratio of mass and compare it to the heavier additional weight.

Steve

[Cyclick]

Greybird:

when you asked "So, everything being equal(ignoring weight), a 6S 5000 pack would fly 43% longer than a 4S 5000 pack?"

The simple answer is a big YES.

My testing have shown that using the SAME mainblades and gearing (changing pinions) for the SAME rotor speed, and using the SAME quality of batteries, you will experience almost that percentage of extra duration (maybe 35% or more), simply because more volts (cells) will require less amps (that which generates heat) so the whole system is more efficient. That increase in efficiency makes up for a good bit of the difference in weight.

[Fred Bronk]

The simple answer is a big YES.

My testing have shown that using the SAME mainblades and gearing (changing pinions) for the SAME rotor speed, and using the SAME quality of batteries, you will experience almost that percentage of extra duration (maybe 35% or more), simply because more volts (cells) will require less amps (that which generates heat) so the whole system is more efficient. That increase in efficiency makes up for a good bit of the difference in weight.

This sums it up well, YES :D

[Greybird]

Perfect.

[Heritic]

Experimenting with parallelling up some of my matched(same mave capacity C rating Kokham 4S4800 and 4S2p4800 both 20C) in actual fact you may get MORE respective duration/useable power as the battery voltage seems to stay slightly higher.
Heritic

[johnm1019]

u might find this helpful
http://www.rcgroups.com/forums/showthread.php?t=919274#post10484918

[Prime12]

At roughly same headspeed, my Swift flies slightly longer with new 8S 3200mAh HV setup than with my previous 4S 5000mAh setup. 4S setup was with Century 600+ and CC60, 8S with Z30A-800 and CC45HV.

If you do the math, the 8S batt has
33.6v * 3.2A = 107.52 amp hours,
the 4S
16.8v * 5A = 84 amp hours.

So the 8S has 20% more overall capacity.

I used to get 9-11min of crusing around on 4s and now I am getting 11-12 with 8S so the calculation is about right.

[Heritic]

So, everything being equal(ignoring weight), a 6S 5000 pack would fly 43% longer than a 4S 5000 pack?


It actualy works out at:-

3.6V x6x5000 = 108000Watts
divide by 4S = 74000 Watts = 45% more power "potential"
Heritic