Calculating current draw and battery capacity.

[randyrls]

Ok; I have a Simple Stick with a B size motor 2212, 35A Esc, 1300mah 30C 3S battery, and 10" 4.5 prop. I've noticed the battery is very warm after a flight. This happens with different batteries. I checked the current with a watt meter and the battery current draw is 18A at full throttle.

According to my knowledge, I should be able to draw 1.3A times 30 current or about 39A from the battery. It is rather cramped in the forward part of the fuselage so there may not be enough cooling.

Are my figures correct?? or am I missing something, or just wrong?

I need to order supplies and may get a 9" 4.5 prop and some hot glue.

Thanks for any help you can give me....

 

[kdobson83]

Your math looks right to me. Below is the spec sheet for the FT branded 2212.

They show about 21-22amps on a 10x4 prop. Now in theory, your 1300 3s 30c battery should be fine. I use a very similar spec battery on most of my swappables on an array of different 2212-2216 size motors and the batteries do get warm, but nothing alarming. But, most of mine are either hanging out in the open or get at least some ventilation.

 

[quorneng]

randyris
Just because your battery is capable of releasing 39A does not mean it will. The current is drawn from the battery by the motor and prop combination.
As long as the actual measured full power amps is below the maximum capability of the motor, ESC and battery then all is well.

In fact extracting the full specified capability of a battery is not really a good idea as it is quite likely just a short duration 'burst' rate. The battery life may be significantly compromised if it is run continuously at its maximum discharge rate.

 

[randyrls]

Your math looks right to me. Below is the spec sheet for the FT branded 2212.

They show about 21-22amps on a 10x4 prop. Now in theory, your 1300 3s 30c battery should be fine. I use a very similar spec battery on most of my swappables on an array of different 2212-2216 size motors and the batteries do get warm, but nothing alarming. But, most of mine are either hanging out in the open or get at least some ventilation.

Thanks; I never noticed the spec listings before. FT may be upgrading their web site to make it easier to use.