Powerex PRO High Capacity Rechargeable AA NiMH Batteries (1.2V, 2700mAh) - 8-Pack, (MH-8AAPRO-BH)I was curious about rechargeable batteries. We have so many choices, so many price points, how do we make a choice. So I decided to do a little experiment. I ordered brand new Panasonic Eneloops (BK-MCCA). The battery claims that it holds a minimum charge of 1900 mAh. The way to think about the charge is "how big is the gas tank". The bigger the mAh, the longer a battery can last. I ordered the Powerex PRO which claims 2700 mAh and minimum capacity of 2550 mAh. I then compared them head to head.How did I compare?To compare the two sets of batteries, I purchased a sophisticated battery tester: https://www.amazon.com//dp/B000RSOV50I set the power to 700 mA and hit charge test. What this does is that it first fully charges the battery, then discharges it completely, and then charges it again to see what the capacity of the battery is. Not an easy process. Four batteries take about 12 hours to test and I was testing 8 Powerex against 23 Eneloops. So it took a bit of patience.And what did the results show?Well, both batteries are made in Japan, and both look nice, in fact Powerex Pro is 4-5 g heavier than Eneloops and comes in a case, but what a difference in the two products. The Eneloops averaged 2030 mAh with standard deviation of 78 mAh. Only 1 of the 23 batteries I tested was lower than 1900. And that too at 1871. In fact, the Eneloops had 6% more capacity than they stated. The quality control was excellent.The Powerex PRO averaged, 1177 mAh, with standard deviation of 133. Note that the tests are identical. I took the brand new batteries and put them in the tester, just like I did Eneloops, and the results were surprising. For those of you who want statistics, I did an unpaired t test, the probability of this happening by chance is very, very small (p<0.0001) . The results tell me that Powerex is 851 mAh lower with 95% chance that it is between 772 and 930 lower.Wait, here is the surprise.I decided to refresh the batteries using a refresh cycle in the charger. Now the results came in more in line. The average power was 2532 with the Powerex, but of the 8 cells, 3 were much below 2550 minimum claim. In fact they were at 1705, 1832, and 1957 mAh. The standard deviation was 602 now.What do I conclude?Well, if you have the time to test Powerex, go for it, because you will find a few strong cells. But if you are looking for overall quality control, the regular Eneloops win. 37% of the Powerex cells were much lower than rated. <5% of the Panasonic cells were below par, and that too within margins of error.Only time will tell how these cells will hold up but this experiment tells me why some folks really love these batteries and others don't. In my opinion, Amazon choice put to the test did not hold up here.Disclaimer: I paid for these products and I do not work for any of the battery manufacturers so I have no skin in the game here. Just trying to get to the bottom of "power game" through some science.