The first question that come’s to your mind when you are building a quad or buying one. How much flight time this quad gonnagive me? Well there are many docs and article on the internet about it, but this one here I am going to make it simple for you to
understand how to calculate it.
Few things you need first to calculate it.
1. Data sheet of your motors (very close or almost accurate)
2. All up weight (AUW) of your model excluding battery.
3. And different set of battery and its specs.
Let’s get started:
Step1: First check the data sheet of the motors that you are planning to use and find the amps its gonna consume for the propeller that you are going to use. Let’s assume that we are using a 2212 980KV motors with 1045 props. And following is the data sheet
|1045||7 V||8 A||540 grams|
|1045||9 V||10 A||660 grams|
|1045||10 V||12 A||750 grams|
|1045||12 V||13 A||850 grams|
The above sheet says that the motor, would give 850 grams of thrust at full throttle and would consume 13A. At 50% throttle it would give 660 grams of thrust with 10A consumption. Lets keep a note of this for now and move to step 2.
Step 2: What are the other components we are using like FC or power module or any other which would take power. Lets assume some extra for these: like 1A to 3A (better to consider higher value)
Step 3: Lets do the maths now.
Consider that your model weight is 1000 grams (without battery) and you have 2 batteries:
First lets find out which lipo is enough or good for your model. How to find it out? is easy. Total motors x each motors power consumption (at 100% throttle)
4 x 13A = 52A + extra say 3A so in all its 55A
If we take first lipo 2200mah 20C which is 2.2 (total capacity in amps) X 20 (max discharge capacity) = 44A which is less than our calculation so this lipo is not suggested.
With the second lipo 3300mah 25C which is
3.3 x 25 = 82.5 which is more than our calculation and this combination is suggested.
So we are going to use 3300mah 25C in our model which is 260 grams total AUW is now 1260 grams, lets round it off to 1300 grams. We would need one motor to generate (1300/4) 350 grams (325 exactly) or more for our model to start hovering. Lets say that you will fly your model at 50-60% of throttle. Then max A single motor would consume would be between 10A – 12A. Lets assume
12A x 4 + 3A = 51A
Now lets take the percentage of this with total cell capacity we got earlier. 51/82.5 gives is 62% refer the following chart.
10% - 25% = 15-20 mins
25% - 50% = 12-15 mins
50% - 65% = 8-12 mins
65% - 85% = 5-8 mins
With the current setup we would get 8-12 mins of flight time. Please note this is just an approximate calculation, it might vary.