Electric Flight in Australia

 

What does C rating for LiPos mean?

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C rating is a way to describe the maximum amps you should draw with a particular pack. If you have a 1300 mAh pack (and that describes the size of the tank - how long a pack will last when you run it - if you draw 1.3A it will last for one hour), it is a 1.3 Ah pack. The C rating is multiplied by this figure to tell you how many amps you can draw safely with that pack.

Manufacturers originally adopted the strategy of describing a pack by the constant running figure, and then giving a figure for what you could draw for a short time without harming the pack - so, a 25C pack might have the C rating attached to it of 25/45C, That means you can draw 25 times the rated capacity of the pack continuously, and 45 times for 10 second bursts.

Take the example of a 1300-3S pack (commonly used in Radians) - if it is a 25/45C pack, you can draw 25 times 1.3A continuously, which is 32.5A. You can also draw 45 times 1.3A for 10 second bursts, which is 58.5A.

Hyperion have now changed the strategy for describing packs and now use the maximum C rating to name them - so, they have 50C G5 packs, but these packs are actually 25/50C packs. You can draw 25C continuously and only 50C for short bursts - so be careful of that one.

If you use small packs at reasonably high Amps (say, in F5J), you need to be careful that you do not exceed the rated amps. Of course, we only run motors for up to 30 seconds in F5J, and my practice is to pull full power for 10 seconds and then switch back to half power to stooge around the sky and use up the allocated 30 seconds without gaining too much height. In this case, lower C rated packs could be used.

High C rated packs of small size are available if required, but they are more expensive.

One final point - the higher the C rating, the better quality the packs and usually the lower the internal resistance of the pack, so buy high-C rated packs for a long life and reliable performance.