|
Flying time
To calculate the flying time depending on your battery pack:
Flying time =
I battery
= minutes.
I e-motor x 60 sec.
For example:
- battery pack = 350 mAh
- I e-motor = 4A
Flying time = 0,350 Ah = 5,25
minutes.
4A x 60 sec
If you don't know the current of your e-motor you can also turn the
formule around.
I e-motor = I battery = A
(t / 60)
For example:
- battery pack = 350 mAh
- 6 minutes flying time
I e-motor = 0,350 Ah =
3,5 A
(6 min / 60 sec)
This is a good indication because you have to consider that the
battery isn't empty when the BEC system kicks in. So in reality the
current is lower than calculated.
Voltage Loss
R = L x r
A
within:
R = resistance (W)
L = length connection + and - wire (m)
r = specific resistance copper (Wmm²/m)
A = surface connection wire (mm²)
U = I x R
within:
U = voltage (V)
I = current through wire (A)
R = resistance (W)
Voltage loss by a surface wire from 0,5mm² from the
battery:
R = 0,15 m x 0,0175 Wmm²/m = 0,00525
W
0,5 mm²
Uv = 7 A x 0,00525
W = 0,037
V
U connection plug = U battery - U loss = 7,2 V - 0,037 V = 7,16
V
Voltage loss by a surface wire from 0,75mm² from the battery:
R = 0,15 m x 0,0175 Wmm²/m = 0,00350 W
0,75 mm²
Uv = 7 A x 0,00350
W = 0,025
V
U connection plug = U battery - U loss = 7,2 V - 0,025 V = 7,18
V
For the total losses in your system you have to measure the entire
wire + and - length.
I don't calculate with the plug resistance because I use gold plugs.
The resistance from these plugs are minimum and don't affect the
voltage losses.
How to calculate the surface connection wire
First you have to measure the wire diameter.>
After this you can use the next formula to calculate the surface
wire.
A = p x r² or
¼
x
p
x d²
within:
A = surface connection wire (mm²)
d = diameter connection wire (mm)
r = radius connection wire (mm)
For example:
d = 0,8mm
A = p
x 0,4² = 0,5 mm² or
A = ¼
x p
x 0,8² = 0,5 mm²
|
|
