I use one for a long time now. Great motor tool.
I just charge ONE pack and let it rest 20 min, then made 5 measurements and change the pack, with another one that had peacked 20 min ago.
Why? Just to stabilize the pack voltage. Remember, you are not competing against each other, you are just measuring your motors, and you'll need a stabilized way to measure them correctly.
I put all the data through my laptop, and monitor every motor.
Every dino gives a diferent measure. For instance the very same 12x1 gives on my CS 214W with 41000rpm/max, but if measured on a Robitronic the Wts will go up, up and up.
I personally use my dino as a reference tool. I measure the motor when new, tunned it to the best numbers I can, and periodically check the motor to see if it can handle the initials numbers. My experience tells that a motor goes up on numbers as you cut the comm then it stars to fall down. When they start to fall down I only used them on practice, being rejected when the arm reach below 6,8mm at the comm.
So don't bother if your dino gives low numbers. Compare all your motors on the same dino and use the best on races.