Hel identifying Cell type....

Hi there,

I have 12 cells which I believed to be LiFePo4 cells, but I am now in doubt.

I bought them off ebay (12 cells, 3.2V, 5500MAh) for less than 20€.
Now I made an 6S2P pack out of them and wondered about their high floating voltage of ~3.5V.
During discharge the cells stayed at said high level and dropped quickly once they got down to ~3.3V and I stopped discharge at ~2.85V cell voltage.

The cells are prismatic black ~120mm long + latches, 3mm thick, and 64mm wide (see picture).

I am getting the feeling that they might be normal LiPo Cells, no LiFePo4 ones, they gave about 4600mAh of their factory charge, which seemed decent.
https://goo.gl/photos/RTHyTqaaTfvWPwey5

Is there any "right" way to identify the cell type?

Well, the 3.2v rating does imply Lifepo4.
A cell of this type will charge up to 3.65v so 3.5ish seems normal to me.
And yes, I've noticed with my Lifepo4 cells, that they will hold a good voltage thru'out their discharge and drop suddenly near the end, whereas a typical Li-ion cell tends to more gradually discharge.

If they are working well in a Lifepo4 application and giving you the capacity they are rated for then I think you're good.
You would get a very low working capacity out of them if they were lipo cells and only charging them up to lifepo4 voltages.
In short, if they were lipo, you'd notice cause they'd give you an abnormally low runtime.

Meanwhile, I'd be more concern that you are using proper balance charging in that pack you built.
I can't really see what you having going on there, but you cannot charge Li type cells in series the same way you would Ni type cells.