Re: [electricboats] Paralleling LiFePO4 battery packs

Best practice calls for paralleling individual cells for a period of time before building them into a battery pack so that they can equalize in voltage.  As long as they are connected in parallel they will remain equalized in voltage.  In a system that parallels multiple cells to achieve higher capacities at a given voltage, the cells would ideally be paralleled BEFORE the series connection.  In such an arrangement, the individual paralleled cells remain equalized in voltage, and it's necessary only to monitor one of them.
In the arrangement you describe, however, while the pre-built 48v packs will remain relatively equalized in voltage, it will still be possible for cells within each pack to vary in voltage by quite a bit.  An advantage of your approach in such a case would be that if one cell in one of your paralleled systems becomes unstable or drags down that pack, you can simply change your connections to take that pack out of the system until you can address the questionable cell.
On the whole, I agree with Ryan that the best answer to your question depends on the capabilities of the integrated BMS.  In some cases, the pre-built units may only have battery protection systems that are designed to respond to over or under voltage conditions, but not offer monitoring or programming.
One other consideration in your arrangement would be somewhat more complicated temperature monitoring.  This becomes an increasingly important consideration as discharge and charging rates go up.  And if you're planning what amounts to a single, large capacity traction battery pack [600Ah], presumably you'll be specifying a high capacity charger [75 to 80 amps].
Just a few thoughts for your consideration ... 
[-tv]

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