# ESC motor and battery matching [closed]

How can you tell if an ESC, brushless motor and Li-Po battery will work together. Specifically, I have a A2212 Outrunner Brushless Motor KV2200, 30A Brushless Speed Controller ESC and I am looking for a battery to run this system.

Motor

ESC

## closed as off-topic by Chris Stratton, Voltage Spike, Enric Blanco, PeterJ, Wesley LeeJun 19 '17 at 2:16

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Chris Stratton, Voltage Spike, Enric Blanco, PeterJ, Wesley Lee
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Most brushless ESCs will run pretty much any 3 phase brushless motor so long as it doesn't draw too much current or spin too fast.

Your ESC is rated for operation at 6-12V, which suggests that you could use a 7.4V or 11.1V Lipo battery. Battery capacity and 'C' rate should match the expected current draw and run time. For example if the average current draw is 15A and you want to get 10 minutes then you need at least 15*(10/60) = 2.5Ah or 2500mAh.

To avoid draining the battery completely you should add 20% to the calculated capacity (making 3000mAh in this example). If peak current draw is 30A then the 'C' rate needs to be at least 30A/3Ah = 10C.

All brushless ESCs have a maximum commutation speed, beyond which the motor may stutter or lose sync. With a Kv of 2200rpm/V your motor will spin at ~11.1*2200 = 24400prm on 11.1V when running free. It has 14 poles, so it is electrically equivalent to a 2 pole motor spinning 7 times faster, ie. ~170000rpm. Some ESCs can handle this high rpm, but others can't (see here for examples). Your ESC's rpm limit is not specified, so you will just have to try it.

Motor current is determined by voltage and loading. With good cooling Your motor should be able to handle ~15A continuous or 30A peak, which on 11.1V is achieved with a 5-6 inch propeller (test data here). Since your ESC is rated at 30A it should be safe so long as you don't overload the motor.

The Motor specs should give you most of the information you need.

To select your battery, you will need to know three values. Battery voltage/cell count, Capacity and Discharge rating.

Usually Hobby motor specs include the number of Li Cells recommended in your battery. If the voltage is listed, divide by 3.7(Voltage of one Lithium cell) to get the number of cells.

Battery capacity is a measure of how much power the battery can hold and is rated in milliamp hours(mAh). You can figure out the Battery capacity you need once you know how much current your motor needs and how long you want to run it. The current rating given is usually the peak current, but in practice you can assume half of it as an average. If your motor takes 10A, a 10000mAh battery should last for one hour. Here is the calculation(ignoring efficiency).

10A = 10 * 1000 mA = 10000mA

10000mAh = 10000 mA * 1hour

For flying applications you will see that you are limited by the weight of the battery and may have to sacrifice the run time based on the weight.

The Battery rating is a measure of how much current you can safely draw from the battery. It is show as 'C' rating, with the common ratings 10C, 20C and 30C. To find the actual current rating, you need to know the Battery capacity too. For a 20C battery with 5000mAh capcaity, the maximum current that can be drawn is 20*5000 = 100000mA = 100Ampere. Chose a battery with higher current rating than the peak current draw of the motor.

The ESC can be selected based on the voltage and the peak current rating of the motor. A simple rule is to choose an ESC with atleast 5A more capacity than the peak rating of the motor, since you may be powering servos, receiver and other accessories from the ESC. Remember to always round up.

This is a rather simplified guide and there are a lot of resources on the web, including calculators that help you match the Motor, ESC and battery.