Why not just get a decent charger where you can set the discharge rate and see what your voltage drop is? Check it every 15 minutes and you can plot your own discharge curve. Not something you want to do all the time as Lithiums don't need to be discharged/cycled anyway. What digitech said makes sense. If the batteries have balancing connectors, then a balancer and a decent charger would let you see how the batteries are performing.

Marty