Quick Li-Po question

[supermaxx4190]

hey guys,
im thinking of making the jump into lipo. i just have a quick question. if i bought some 3.7 volt 4000mah lipo cells, how many will i need to have 2 packs of 7.4 volt 12000mah packs? the cells are rated at 6C continous and 10C max. so that would leave me with 72 amps continous and 120 max. would my 8L motor on 12 cells draw too many amps for these packs? the truck is 10-11 pounds geared 15/70. thanks
Isaac

[supermaxx4190]

i just figued it out...i think i would need 2s 3p per pack, so 5 cells per pack or 10 cells all together. well do you think the packs can handle the amp draw?

[RC-Monster Mike]

Yes. you figured it out(except it would be 6 cells per pack and 12 cells altogether), and yes, the packs should handle the amp draw with no sweat.

[supermaxx4190]

actuly im pretty sure its 10 cells altogether.

3.7 times 2 is 7.4 volts

4000 times 3 is 12000 mah

mike, mabey your thinking im trying to make 16000 packs like before. if i can get away with 10 cells and the batts can take the amp draw, im only gonna make 12000 packs. so how many amps on average do you think the 8L draws? it would be WOT on the track.

i think im gonna sell my truggy and buy some lipos and a m8/ spectrum radio system. i dont want to worry about 2 trucks

[RC-Monster Mike]

Something is breaking down in your math, my friend.

3.7*2 is 7.4 - true
4000*3 is 12000mah - also true

So, 3 times 2 parallelled cells is .....6! You will need 3 sets of 2p cells(so 3 times 2 = 6).

I am pretty sure you will be fine with this setup(just make sure they fit in your truck).

[supermaxx4190]

man i am confused..can you just draw a quick diagram:C:

[RC-Monster Mike]

I am no artist, but I will try to explain it a little better. Lets build one pack together:
In order to get 7.4 volts, we need 2, 3.7 volt cells (already established)

Let these represent the cells: II

Now, to have this 4000mah, 7.4volt pack become a 12000mah, 7.4 volt pack, we need to run two more sets of the same thing
(II + II)

So, altogether we need three sets of 2 cells per pack ( II+II+II) wired in parallel. So the total cell count per pack is 6.

[supermaxx4190]

i know that, but how do you wire them in paralell?

[RC-Monster Mike]

Wire all positives together and all negatives together.

[supermaxx4190]

im pretty proud of myself :L: :D ...
is this right? pretend ech one of the packs represents a 4000mah 7.4 volt pack.

[RC-Monster Mike]

You got it. Better drawing than I could have come up with! :)

[supermaxx4190]

YAY:L: :L: :L: :cool:

[RC-Monster Mike]

;)