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« on: July 16, 2009, 02:02:59 AM »
anwar
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Watch this carefully, the information is extremely useful  Clap



And almost everything you want to know about LIPOs are summarized here :

http://www.rchelicopterfun.com/rc-lipo-batteries.html



« Last Edit: February 16, 2010, 02:01:35 PM by anwar » Logged

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« Reply #1 on: July 18, 2009, 12:53:25 PM »
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This is great , why not have a learning thread like the one on propeller :

The common terms used to describe a battery are :

Volt
No. Of Cells
MAH
Discharge capacity .

Eg
Volt : 11.1 V ( max charge 12.6 V )
No. of cells : 3 S
Mah : 1000 mah
Discharge capacity : 15 C

What does 15 C Mean and what is its significance  other things are fairly straight forward.

In theory how many amps can be drawn from this battery ?

I know these things are covered in the Video but just in thought a written explanation from the knowledgeable  on the forum  would help .

Sai
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« Reply #2 on: July 19, 2009, 01:23:31 AM »
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I'm sure you all know this very much already. Anyway, 'C' is the discharge capacity of the battery pack. So given the charge capacity (in this case) 1000mAh, the discharge capacity of the pack is (C rating x charge capacity). In this case we have 15000mAH or 15 AH (amp hour). And, if current draw is at this max.  level - 15 amps - the battery will be discharged in 4 minutes Or if the current draw is 1 amp then the battery will discharge in 15 hours. Correct??
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« Reply #3 on: July 19, 2009, 11:57:48 PM »
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I spent hours in internet to know about the lipo. with these info i understood something about this strange "C" rating. "C" rating is seen on lipo batteries only, the reason is the chemistry of this battery. In lead-acid battery the discharge rate can be very high, tats why its still used in automobile for starter motor. hence the calculation in the above post is vaild. that is, for a 15Ah(15,000mAh) lead battery(also for NiCd and NiMH) the power stored is 15Ah. if we consume at the rate of 1A per hour, the battery will come for 15 hours. similarly if v consume 150 A, it will come for just 1/10 hour(6 mins). that is the power stored in the battery is a constant and the rate at which we consume the energy will decide the time. Best analogy is a water tank, in which the water content is power and the rate at which we tap the water will decide the water content inside the tank empty. In lead battery the pipe connected to the tank can be of any size, may be big or small( can draw huge current or very small current). In any case it will give its energy without damaging the battery.

coming to lipo, the chemistry of lipo is different from lead acid ones(also NiCd and NiMH). The current drain rate(water tapping) is limited, so we can use only a small size pipe to the tank, unlike the lead acid type. so the "C" rating comes to picture here. we rarely come across a lipo greater than 5000 mAh capacity(water in tank).

lets take an example, we have a 3s lipo(11.1V) 1000mAh 25C, it means the total battery can be consumed in 1/25 of an hour(2.4 minutes) max. if we consume at a higher rate than this, we will end up in a damaged battery. so the maximum current drawn may be 25A. it can be simple to use this formula,

                         Rated capacity(mAh)    X    C-rating      =       maximum safe current(mA)

 eg, a 5000mAh LiPo battery pack with a 20C rating can safely provide 20 x 5000mah = 100,000 mA or 100 amps. hope it gives some idea on "C" rating. pls correct me if i am wrong anywhere.
« Last Edit: July 20, 2009, 12:10:29 AM by akash » Logged
 

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