PDA

View Full Version : Speed Controllers


JLK
10-18-2005, 01:41 PM
How do I know what Amp rating speed controller I need for a given LiPo voltage and capacity and motor size?
Thanks!
JLK

U2Steve
10-19-2005, 03:50 AM
It depends. You're working backward, a little. You first have to know the current draw of the motor (and gearbox, if any) and the prop. This info is always someplace in the paperwork or the package that the motor came with. Then you pick an ESC based on this, then you pick a Lipo that can handle that much amperage.

Hope that helps,

Steve

kalel
10-28-2005, 12:34 AM
That is good info. What is the C value that everyone talks about with lipo (ie. 12C with 20C bursts)? I understand voltage and amperage.

timocharis
10-28-2005, 12:52 AM
Big C is the charge value of the battery. For example, if you have a 1200 MAH LiPo, 1200 milliamps is 1C. 10C would be, of course, 12 amps.

Small c is the speed of light.


Dave North

qban_flyer
10-28-2005, 12:59 AM
That is good info. What is the C value that everyone talks about with lipo (ie. 12C with 20C bursts)? I understand voltage and amperage.

The "C" value is the battery capacity in Amps (or milliamps). When you read that a battery will handle a continuous 12C discharge rate it means that it can be discharged at a rate 12 times its stipulated capacity.

For example: 12C of 1 Amp (1000mAh) = 12 Amps, 12C of 2 Amps is 24 Amps and so on.

Burst refers to how much the pack will handle for a short period of time, though as far as I know, no Li-Po manufacturer has specified the duration of that short burst yet.

A 20C burst of 1 Amp will equal 20 Amps, and 20C of 2 Amps is 40 Amps and so on and so forth.

So if the 1000 milliamp pack is rated at 12C continuous discharge rate you can discharge it at 12 Amps without fear of damaging it. The 20C burst will allow you to discharge momentarily (who knows for how long) at a rate of 20 Amps).

It would be nice if all manufacturers would stipulate in their spec sheets what the burst duration of their packs really is.