Calculating Required Battery Capacity for build

[Jonas104]

Quad is finally in flying and FPV ready condition. Need to tune it up and after that, I will be looking for more batteries. Keep in mind I just learned these formulas, so apologies if I totally misunderstood how to use them.

I currently have to (x2) Pulse 4S, 75C, 1550 mah batteries. If I understand correctly, max amps out = C * mah. So, 75 * 1.5 = 112.5 amp max draw.

My ESC's are Little Bees 20A (20 amps right?) not sure what the burst rating is or if there is any, so that means I'm drawing about 80 amps.

Can someone please help me figure out the rest. I just want to make sure I'm not spending more money than needed. I'm also open to recommendations on batteries, I'm just starting out so I don't mind trying a few different ones.

Thanks guys!

 

[Old Man]

Might want to perform a test where one motor/prop combination is run at full load and capture the amp draw. Multiply by the number of motors and add in for any other power draws that will be functioning at the same time.

As for batteries, my experience has found buying somewhat more expensive but highest quality batteries is cheaper in the long run than using the least expensive I can find.

 

[John Doecliff]

You may be able to look up your motors on the web. they usually list current draw at different throttle settings and props. Just cause you have 20 amp ESC's doesn't mean that's your current draw. A higher C rating is preferred if you can afford it but not always necessary.

 

[Old Man]

Even better would be to weight down the copter to where it can't possibly lift off, put an ammeter in line with the power supply, and watch what shows up on the meter when you quickly advance to full throttle. That value will be the most accurate you can get short of recording current loads while in actual flight. I use a "WattsUp" meter for this purpose on new builds or after making changes that could impact current loads. It's small enough to fly with and records the peak load for later viewing.