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01-04-2015, 10:19 PM #1
 Class 1 Laser Join Date: Mar 2012 Location: North Carolina Posts: 76 Rep Power: 6
r1Bro
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Calculating battery amps of multiple Li-ion cells

If you have a li-ion 18650 (2600mah each) pack made of 9 cells in total (groups of 3 for a total of 11.1volts) would this battery give an output of 23 amps?

From a few Google searches it says that batteries in series wont increase the mah? So 3 groups of 3 2600mah batteries for 11.1v would be 7800mah? or 7.8amps?

I want to confirm how strong this battery will be, I have a driver which has max input of 16A and I don't want to kill the driver with a battery too powerful. So if anyone can help me understand this better that would be great!

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01-04-2015, 10:53 PM #2
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Pi R Squared
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Re: Calculating battery amps of multiple Li-ion cells

Quote:
 Originally Posted by r1Bro If you have a li-ion 18650 (2600mah each) pack made of 9 cells in total (groups of 3 for a total of 11.1volts) would this battery give an output of 23 amps? From a few Google searches it says that batteries in series wont increase the mah? So 3 groups of 3 2600mah batteries for 11.1v would be 7800mah? or 7.8amps? I want to confirm how strong this battery will be, I have a driver which has max input of 16A and I don't want to kill the driver with a battery too powerful. So if anyone can help me understand this better that would be great!
Your not quite making sense here, the driver needs a voltage within a certain range, it will then draw whatever current it needs from the batteries. You can't kill a driver with a battery too powerful unless it's too high a voltage. The mAh number just refers to the power capacity of the battery (how long it will last), if it were 7800mAh that means it can put out 7.8A for 1 hour or 3.9A for 2 hours or 15.6A for half an hour etc.

Alan
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01-04-2015, 10:58 PM #3
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r1Bro
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Re: Calculating battery amps of multiple Li-ion cells

Quote:
 Originally Posted by Pi R Squared Your not quite making sense here, the driver needs a voltage within a certain range, it will then draw whatever current it needs from the batteries. You can't kill a driver with a battery too powerful unless it's too high a voltage. The mAh number just refers to the power capacity of the battery (how long it will last), if it were 7800mAh that means it can put out 7.8A for 1 hour or 3.9A for 2 hours or 15.6A for half an hour etc. Alan
Okay thank you, you cleared it up. I was confusing the capacity for amps. I see now that the driver will only draw what it needs. I was thinking the capacity was too much for the driver to handle. Thank you, I understand now!

01-05-2015, 10:05 PM #4
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Cyparagon
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Re: Calculating battery amps of multiple Li-ion cells

The notation for this configuration is 3s3p (3 series 3 parallel). Two of those in parallel would be 3s6p, etc. Adding cells in series adds in multiples of the voltage, while the "mAh" capacity remains the same. Adding cells in parallel adds in multiples of the "mAh" capacity, while the voltage remains the same.

As for any current rating, it depends on the lithium cell used to construct the pack, as well as the wiring (to a lesser degree). I believe convention for standard lithium is 2C discharge, which means in your case up to 15.6 amps is okay. 23A is okay for shorter durations.

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