# battery mAh

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Does anyone here know how to calculate mAh capacity of single inside a laptop battery, if you know the number cells the voltage of individual cells, the battery's output voltage and battery's mAh.

anyway here is what I have

8 cell battery

each cell at 3.7 volts

battery out put voltage 14.8 volts

with 4000mAh capacity

what I need to know th mAh of one cell.

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so it looks like the battery is made up of two banks of four cells

4 x 3.7 V = 14.8 V

each bank should have 2000 mAh... which means that each cell also has 2000 mAh as they are in series, so the voltage increases while the current/capacity stays the same

putting two banks of 2000 mAh in parallel increases the current/capacity, 2000 mAh x 2 = 4000 mAh, while the voltage, 14.8 V, remains the same

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What kind of cells are they??

Ni or Li??

from what you are telling me (each cell is 3.7) then I would guess LiIon which have a nominal voltage of 3.7v....full charge is 4.2v per cell....

NEVER take them lower than 3.0v per cell under load as that will damage them...

So.... since your pack has 8 cells.... each cell is 3.7v....that is 29.6v....

but your voltage is 1/2 that so it is 4 cells in series... then the the 4 cells are hooked to the other 4 cells in parallel....

all that said....

I would guess each cell is a mAh of 2000mAh....

Lots of info here....

http://www.rcbatteryclinic.com/

I fly RC airplanes and we use all kinds of different batteries.......

I think my math is correct

I think so too

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Lol!

Actually, since I've been involved in RC aircraft...I have learned more than I thought existed with batteries....

Now we are talking about a123, Nano phosphate LiIon batts..... and LiMn batts and all kinds of stuff..........

Here is my baby with dual Fromeco 5600 mAh Lion packs for the Recievers and 1 2400mAh pack for the engine ignition!

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Awesome! I'm curious, what size/type engine does that thing use?

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It is a 40% replica of an Extra 330S

Weighs in at 40lbs...

10ft wing span

Engine is a Desert Aircraft 150cc twin

Specs and info here

http://www.desertaircraft.com/engines_detail.php?Page=DA-150

Prop is a Mejzlik 32 x 10 carbon fibre prop.......

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thx for the help every one, hardnrg the battery layout right. This info is for a laptop battery rebuild and yes they are li-ion cells, I was just looking for the mah so I could figure out my rough mah gain on 2600mah cells. by my calculations it appears it would be a 1200mah gain ~1.2AH hardly worth it for the extra \$30 it would cost for only about 30 minutes of extra power oh well. btw does anyone know where I might get some cheap li-ion type 18650 cells in the US. they 18mm diameter x 65mm lenght, the lowest price I have seen is \$3.50 each for 2200mah.

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have you checked eBay for a complete battery? many places sell 3rd party or OEM batteries that are a lot cheaper than the original brand

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yes I have checked ebay for a complete battery cheapest I found \$90 before shipping.

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so \$28 for the 8 cells isn't very much eh... man that's only