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Old Nov 09, 2005, 10:52 PM
Lets go brushless
skid_68's Avatar
Utah
Joined Oct 2005
131 Posts
Question
What is the formula for lipo discharge amps? C ratings and such?

Formula may not be the right word here, but I cant remember how to figure out how many amps my pack can put out. I have a 7.4v 2s 1800mah 10C lipo. Is it just 1.8(1800)x10(10c)? So it can put out 18 amps?
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Old Nov 09, 2005, 10:56 PM
UAV's are my bag... baby.
direwolf's Avatar
Rapid City, South Dakota
Joined Oct 2004
356 Posts
Quote:
Originally Posted by skid_68
Formula may not be the right word here, but I cant remember how to figure out how many amps my pack can put out. I have a 7.4v 2s 1800mah 10C lipo. Is it just 1.8(1800)x10(10c)? So it can put out 18 amps?
Yes. Multiply the "C rating" by the battery's max capacitance (mAh) to get the maximum continuous discharge rate the pack can handle.

-- Brian
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Old Nov 09, 2005, 11:02 PM
Lets go brushless
skid_68's Avatar
Utah
Joined Oct 2005
131 Posts
So I was correct with 1.8X10 right? So my 10c pack can put out 18amps constant? Thanks.
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Old Nov 09, 2005, 11:10 PM
UAV's are my bag... baby.
direwolf's Avatar
Rapid City, South Dakota
Joined Oct 2004
356 Posts
Quote:
Originally Posted by skid_68
So I was correct with 1.8X10 right? So my 10c pack can put out 18amps constant? Thanks.
Yup. Exactly. For example, I own a couple 15C 2100mAh batteries. They can handle 15*2.1 Amps or 31.5A continuous discharge.

Also, remember that you should never charge LiPo's faster than 1C. In your case, don't charge your 1.8Ah battery any faster than 1.8A, or else you could seriously damage the battery, or maybe even start a fire. If you have enough time to wait for the battery to charge, then charge it slower than 1C. Charging at .25C can greatly increase the life of the battery.

-- Brian
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Old Nov 09, 2005, 11:40 PM
Lets go brushless
skid_68's Avatar
Utah
Joined Oct 2005
131 Posts
Great, thanks Direwolf. Much appreciated, didnt want to melt down my batt. My new Brushless is the most efficient @ 18amps, and my current power setup with my prop puts out about 17.5 amps. So looks like Im spot on with everything. Just cant wait to fly it now.
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Old Nov 10, 2005, 06:45 AM
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Brian, a word of caution: manufacturer's C-ratings have proven to be overstated in many cases. Look for your particular LiPo brand in the battery graph vault.

If it's there, the graph will give you an accurate picture of your LiPo's capacity and discharge rate capability.

- RD
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Old Nov 10, 2005, 09:10 AM
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For example, see:

http://www.rcgroups.com/forums/showp...89&postcount=1

The information published at point-of-sale claims 15C/90%, but the graph reveals only about 40% of capacity discharged @ 15C.

10.5C is about right for this LiPo.

- RD
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