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Old Jul 10, 2012, 10:57 PM
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United States, MD, Cambridge
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Help!
Increase "C" rate when parallel charging?

I'm by no means a battery expert, as will probably become apparent after I pose my question... But let's say I charge 1 battery pack set at 1C and it takes 15 minutes to charge; If I were to charge 4 of the same batteries at 1C on a parallel charging board, it would take approximately an hour. My question is (assuming my previous sentence is correct), would bumping the "C" rate up to 4 while parallel charging effectively charge each pack at 1C? And if so, would that bump the charging time back down to 15 minutes?
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Old Jul 10, 2012, 11:33 PM
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So. Cal.
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When you connect 4 packs of the same capacity in parallel, you have just created a single pack with 4 times greater capacity than a single pack. As such, 1C charge rate will be 4 times greater than it would be for a single pack.

In your example, you are not 'bumping the "C" rate', you are keeping it the same but it happens to be 4 times greater current as capacity is 4 times greater.

Mark
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Old Jul 10, 2012, 11:36 PM
Expo/DualRates = Lack of Skill
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San Diego, CA
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It's sounds like you are confusing amps with the C rate.

A 1C charge should take about an hour regardless of the battery size. (When charging a fully discharged battery.)
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Old Jul 10, 2012, 11:46 PM
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Thanks for the replies, guys. I think you're right, I may have amps and C rating confused. I actually have 4 packs charging right now and I have to wait til they're done to verify.

I'm charging four 2S 1000mAh lipos right now. I have the amps (or C rating as I thought it was earlier) set to 1.0, and it's taken over 2 hours to charge. So it sounds like regardless if I increase the amps to 4.0, it's still going to take 2+ hours?
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Old Jul 10, 2012, 11:57 PM
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1C for one 1000mAh battery is 1A. At 1A it should take about one hour to charge.

Four 1000mAh batteries in parallel is 4000mAh = 4Ah. 1C for 4Ah is 4A. At 4A it should take about one hour to charge

If you are charging 4Ah at 1A, it is only 0.25C and should take about 4 hours to charge.
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Old Jul 11, 2012, 09:46 AM
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Quote:
Originally Posted by jkettu View Post
1C for one 1000mAh battery is 1A. At 1A it should take about one hour to charge.

Four 1000mAh batteries in parallel is 4000mAh = 4Ah. 1C for 4Ah is 4A. At 4A it should take about one hour to charge

If you are charging 4Ah at 1A, it is only 0.25C and should take about 4 hours to charge.
Well when it finally finished, it took about 2 hours, 20 minutes. Of course they weren't completely dead or anything, so perhaps that's why.

So in looking at your explanation, when charging the same packs as described above, I CAN increase to 4.0 amps, which would effectively charge each pack at 1C, which should take approximately 1 hour?

The point of my question I guess is that I know when charging a lipo pack, it's not a good idea to charge at too many amps. If I'm in a hurry I'll set it at 2.0, but I generally try to keep it at 1.0. In my mind, if I'm charging multiple packs, I can double, triple, quadruple, etc. the amps, dependent on the number of packs I'm charging. So I can set it at 2.0 to charge 2 packs @ 1.0, set it at 4.0 to charge 4 packs @ 1.0, etc. Seems like simple math in my mind, but electricity might not adhere to simple math

Sorry if I keep asking the same question in a loop... I still can't quite grasp it, but it'll eventually *click*.
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Old Jul 11, 2012, 09:53 AM
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No-one will object if you ask questions until you understand. And you do understand this issue, your comments about charge currents are correct.

Electricity does adhere to simple math, always. That's why electric systems are so much easier to understand and use than internal combustion.
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Old Jul 11, 2012, 10:14 AM
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Quote:
Originally Posted by jkettu View Post
1C for one 1000mAh battery is 1A. At 1A it should take about one hour to charge.

Four 1000mAh batteries in parallel is 4000mAh = 4Ah. 1C for 4Ah is 4A. At 4A it should take about one hour to charge

If you are charging 4Ah at 1A, it is only 0.25C and should take about 4 hours to charge.
Short and sweet. Like.
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Old Jul 11, 2012, 11:13 AM
Southern Pride
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Haralson County GA. USA
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All one needs to know about parallel charging,

http://www.rcgroups.com/forums/showt...light=parallel

Charles
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