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can i connect 4 11.1v lipo batteries in series AND parallel?

i have 4 11.1 v 2200mAh  lithium polymer batteries, and i want to connect 2 in series to give me 22.2 v with same aH and connect the remaining 2 in parallel to  give me 11.1v but 4400mAh. 
is the a configuration of the two pairs i can do to archive max voltage and mAh.

thanks in advance.

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-max-2 years ago

Before connecting batteries in parallel, make sure they have exactly the same voltage potential across them. They should also have the same voltage ratings obviously. NEVER connect batteries in parallel when one of the cells are different from the rest (in terms of voltage, charge, battery technology, etc) I think that batteries connected in parallel, you do not need to worry about the capacity differences, because essentially once they are connected they can be thought of as one large cell. The reason is because if one is much lower capacity, as the voltage begins to sag on it, the other batteries begin to take over and power the load and allow charge to flow back into the cell that is not delivering. Luckily this is a negative feedback loop whereas one cell begins to show a lack in capacity, other cells will take over and keep whatever running, and minimal additional stress is put on the battery.

When connecting cells in series, it is the other way around, where tight capacity tolerances (mAH) are HUGELY important, while voltages are not. For instance, a 2200mAH 2S battery can be connected in series with a 1S 2200mAH battery of the same age. the 2S battery is made up of 2 cells in series, and thus the whole system is like a 3S battery. However, again do not use different battery chemistries or capacities in this config. Also if you plan of charging or discharging at high currents, you will need to keep the batteries balanced since there is always a bit of play in the capacities of the cells and one cell will always die or charge faster than the others. In series, that is especially bad if nothing is done about it, it means the battery with the least capacitance will be stressed the most, causing it to become even worse and possibly damage it or destroy it! (it is a positive feedback loop or a chain reaction type effect). Just make sure to keep them balanced.

Considering all that, I would do the exact opposite and wire 2 sets of cells with matched voltages in parallel, put them together and treat them as a single large cell (because it essentially is) and wire the 2 sets in series. That will get you 22.2V @ 4400mAH. A assume you are not trying to achieve a specific voltage or capacity...

icey.hood (author)  -max-2 years ago

ive decided to connect them in pairs 6 batteries @ 33.3v and 4400mAH.

im making a battery powered coil gun.. each coil draws about 180-200 amps of a pulsed current. I want to know what fuse i should use to protect the circuit.?

-max-2 years ago

I will interpret what you mean by "max voltage and mAh." as "maximum energy"

energy (WH) = AH times avg.voltage.

Well, you can combine all cells together in parallel to get 11.1V @ 8800mAH,

or you can combine them all in series to get 44.4V @ 2200mAH,

or you can do what I said below and get 22.2V @ 4400mAH.

REGARDLESS of you pick, all 4 options will offer you 4 times the about of WH as before, so pick the option that best suits your load. If you are powering existing circuitry you used to power with one of those packs, then I'd go with the first option so the voltage is the same and you will bet about 4X the run times. Any other option might lead to the magic smoke with electronics and voltage regulators.

icey.hood (author)  -max-2 years ago

can i have 2 packs in parallel and the other 2 in series with the parallel packs.

wouldnt that give me 33.3v @4400mAh?

-max- icey.hood2 years ago

(Some reason instructables is not showing your next question... ) You can connect 2 batteries together in a way that it will be like 2 pairs of paralleled packs in series or combine them together to make 2 packs that are made up of 2 batteries in series, then parallel those together. That would yield 22.2V @ 4400mAH (either case the pack is 2P6S (6S because 3S+3S = 6S))

Drawn in schematic form it would look like a square grid or rectangle of batteries. What I am saying you cannot do is have them wire them in such a way that there will be 2 batteries paralleled up with the remaining two both in series with that back. The 2 batteries that are parallelled up can be thought of as one big battery with twice the capacity, and remember what I said about series batteries with different capacities...

-max- icey.hood2 years ago

Assuming I understand correctly, No, it won't. You can't do that because the 2 batteries in series will drain before the 2 in parallel fully discharge. This will leave power in the 2 paralleled cells and trying to use that power while it is wired the way you describe, you will over-discharge and possibly reverse charge the series cells. As the old saying goes; a chain is only as strong as its weakest link.

Pair them off in series and then wire the pairs together in parallel will give you the 22.2V and longer run time your after. Just be aware you will have to separate the batteries to charge them.