Math Help ( Hey, I'm new to this stuff ) Thought it was a simple multiplication problem

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scouttster's picture
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Joined: 12/19/2011
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Gentleman is selling batteries as reads:
$58.20 for 28 = 3.7v 2400mah batteries.
Enough to make a 25.9v 9.6ah pack that works with the EZip 24v controller!

I figured he arrived at his figures by 28 X 3.7 for the voltage and 28 X 2.4 for the amphours. I was way wrong.. Can someone explain, how he arrived at 25.9 Volts and 9.6ah?
Thanks, I'm new to all this and just trying to learn.

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Re: Math Help ( Hey, I'm new to this stuff ) Thought it ...

Cells in parallel add AH, cells in series add V.
So, 4 cells in parallel = 2400mAH x 4 = 9.6AH (still 3.7V)

7 x series string of 4 parallel cells = 3.7V x 7 = 25.9V (still 9.6AH)

scouttster's picture
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Re: Math Help ( Hey, I'm new to this stuff ) Thought it ...

Just trying to visualize it to help me learn..

So, that would be seven batteries wired or connected in series and called a string?
There would be four of those strings and you'd wire those in parallal to get the 9.6ah?

Also, any special reason its called a string? Define string?

Thanks for the reply and clarifying.

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Re: Math Help ( Hey, I'm new to this stuff ) Thought it ...

The above is correct.
String = bunch of cells, either in parallel OR series..

Normally like this...
(Xp,Xs) or (Xs,Xp)

P = parallel
S = series

Parallel you add up Ah
Series you add up Voltage

(7s,4p) = (4p,7s)

7s = 7 x 3.7v = 25.9v
4p = 4 x 2.4ah = 9.6Ah

Btw? Where are you getting these? Does he have more? Sounds like a good deal.
Inquiring minds want to know.

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