Can three packs be run together?

[Fyrfytr]

I was wondering if it is possible to run three packs together. I'm building 6s A123 packs and thought maybe running two in parallel and then hooking the third up in series. I know that connecting it up would be possible. I was just wondering if the packs would discharge evenly or how that would work.

[Pinecone]

If you put any two packs in parallel and a third pack in series, you will kill the third pack. The amp draw will be twice as high and you will have only half the capacity.

If you want to parallel and series, you need at least 4 packs.

[istandalone]

now that would be a heavy sum-biatch!

[Fyrfytr]

Why would the amp draw be twice that on the pack in series? I'm just wondering due to reading about guys running 2300mah A123's and 1100mah A123's in the same pack. I was just wondering if the cells might balance their voltage out in flight somehow or something else which might make it possible. Well just a thought for expanded mah with a HV twist.

[Pinecone]

You can run 2300 and 1100 cells in parallel and then series the resulting packs.

The allowable amp draw and amount of mAH available are based on the lowest performance pack in the series.

What you are trying to do is put a 4600 mAH pack in series with a 2300 mAH pack. Say all packs are 20C (makes the math easier). So the 4600 pack will deliver up to 92 amps. But the 2300 pack will only deliver 46 amps safely. So if you draw 75 amps, you will kill the 2300 pack.

And the 2300 pack will only deliver 2300 mAH, so if you draw 3000 mAH out of this setup, you will kill the 2300 pack.

So basically you are carrying the weight of the 3rd pack for NOTHING.

[Fyrfytr]

Thanks for the reply! I'm still learning as much as I can about electric so I appreciate your time in explaining it to me :thumbup: