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Go Back   HobbyTalk > Radio Control Vehicles > Brushless RC Motors & LiPo Batteries
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  #1  
Old 10-20-2008, 01:35 PM
RCThunder RCThunder is offline
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What does 'C' rating mean?? Does it matter??

I get this question a lot. Maybe a thread to get some discussion going. Here is an article my friend Paul Schaub found below. The question is how much amperage are we really using?

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So what does the “C” rating on a lipo mean?
For starters, the ‘C” in “C Rating” stands for capacity.

To break it down to its simplest terms, the “C” rating is the maximum safe continuous discharge rate of a pack. If you see 10C on your battery, it means it can be discharged at 10 times that pack’s capacity. “Capacity” refers to the milliamp-hour rating of the battery, which will be listed as a number followed by mAh (2000mAh, for example). Here’s the easy way to find your battery’s discharge rate – just multiply the number from the “C” rating by the pack’s capacity. Keep in mind that 1000 milliamps equals one amp.

Here’s an example, using an 11.1V – 2000mAh – 10C:
2000 milliamps = 2 amps, 2 Amps x 10 = 20 amps continuous discharge.

This means that you can safely draw up to 20 amps continuously from that 11.1V – 2000mAh – 10C without doing damage to your battery.

What does the "C" mean in 10C, 20C etc ?
We use the designation 10C etc to mean how much a cell or pack can discharge in amps. C always equals the capacity of a cell or pack. For example. Let use a PQ31003S pack rated for 12C. In this case C=3100mah. the number before the "C" is the multiplier. so 12 x 3100 = 37200mah. to get amps we simply divide by 1000. 37200/1000 = 37.2 amps. 1000mah = 1amp.

So for the above pack (PQ31003S) rated @ 12c we now know the max discharge rating is 37.2 amps.

Another example: a 20C 1800mah 3S pack.=2 0What is its max rating? 20 x 1800 = 36000. 36000mah = 36000/1000 = 36amps. So the 1800 3s pack @ 20c has a max rating of 36amps.

So when ever you see a C rating take the number before the letter "C" and multiply the packs capacity by it. That is it. To get amps from your new number simply divide it by 1000mah.

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  #2  
Old 10-20-2008, 01:50 PM
swtour swtour is offline
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Quote:
Originally Posted by RCThunder
The question is how much amperage are we really using?
Mike,

Get your hands on a NOVAK Sentry system, or a Eagle Tree E-Logger and you can answer that question yourself.

21.5/LIPO on Carpet geared for 5 minute racing (In one of the FAST Guys cars) pulled high to mid 40's for less than ONE second off the line.

Off the corners it pulled about 20-21 amps, and going in at the other end was reading about 16 amps.

On our VELO, the 21.5/LIPO pulled about 21-19.5 amps from start to finish in (5) minutes.
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Old 10-20-2008, 01:53 PM
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davepull davepull is offline
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Mike call me wtf. but the biggest problem with c rating is there is no "industry standard" for testing. the manufactors can do whatever they want so company xyz says there 5000 pack is a 28c doesn't mean it is the same 5000 28c from company abc.

the differences it the c rating testing is so wide on companies 28c is anothers 23c etc... IMO c ratings are usless.
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Old 10-20-2008, 05:53 PM
pmsimkins pmsimkins is offline
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The technical definition of the C rating is really not of much value as even a 15C 3000 mAh pack would supply sufficient current (for higher turn oval racing).

The practical definition is of more use. When you have a higher C rating the pack generally has lower internal resistance (this is how it is able to supply more current). Lower internal resistance means that your pack's voltage will not depress as much under load. Consequently more performance.

I don't care what C rating is printed on a battery, since like Dave said many of them are BS'ing. All that matters is where it cycles on the GFX.

Last edited by pmsimkins; 10-20-2008 at 06:04 PM..
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Old 10-20-2008, 06:12 PM
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Z-Main Loser Z-Main Loser is offline
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Try this.

http://axonracing.com/catalog/media.php

Watch the video "Selecting the right Lipo Battery"
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Old 10-20-2008, 06:44 PM
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WLMaye WLMaye is offline
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Quote:
Originally Posted by Z-Main Loser View Post
Try this.

http://axonracing.com/catalog/media.php

Watch the video "Selecting the right Lipo Battery"
Very helpful. Hey anybody gonna run those hover crafts on an oval track?

Bill
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Old 10-22-2008, 02:14 PM
trailranger trailranger is offline
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Quote:
Originally Posted by davepull View Post
the biggest problem with c rating is there is no "industry standard" for testing. the manufactors can do whatever they want so company xyz says there 5000 pack is a 28c doesn't mean it is the same 5000 28c from company abc.

the differences it the c rating testing is so wide on companies 28c is anothers 23c etc... IMO c ratings are usless.
I think C ratings are somewhat overrated and not compareable between companies.

I think a new approach should be used to rate batteries.

I would like to suggest PEAK WATTAGE for battery ratings!

Just like Lead Acid Batteries have CCA rating for the maximum amps produced without the battery voltage going under 7.2V for a 12V PB battery

Peak Wattage would be the maximum wattage produced by a LiPO without going below 3.0V per cell or some other voltage cut-off. The test could be a simple test where the starting current is 1C and increases 1C every second untill the voltage cuttoff is reached or a reduction in wattage. The ramp-up in amperage at a constant rate would eliminate errors caused packs that are only good for the a short burst of amperage vs. the actuall race conditions.

The reason I would rather see peak wattage because the voltage drop on batteries can skew the results. At somepoint the voltage drop is more rapid than the increased amperage reducing the total wattage. It would be a simple standard for everyone to adapt and racers could compare batteries more easily
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Old 10-22-2008, 04:12 PM
Johnny Wishbone Johnny Wishbone is offline
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The companies have set a standard for the "C'" ratings and is as follows;

C=chaaching

The higher the "C" the more chaaching it will cost you.
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Old 10-22-2008, 05:08 PM
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hankster hankster is offline
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There has never been a "standard" for RC battery numbers, why should we expect anything different now?
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North Fort Myers Weather - http://www.northfortmyersweather.com/weather/

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