Energizer Ni-MH cells made since 3 years ago also hold their charge for a long time like Eneloops. They are also made in Japan. Coincidence or same Sanyo/Panasonic manufacturer?
A battery charger IC follows common advice for charging Ni-MH cells by detecting the voltage leveling or voltage drop that occurs when the cell is fully charged, not simply the actual voltage it has risen to.
You just never know, and it can change from batch to batch. Anybody can stick labels on. Rechargeable batteries are awkward to make and the proper manufacturers do a load of test to ensure that the baterries will be ok in the field. But even so, some still fail. The second line and rip-of types either arn't made and tested so well or are possible rejects.
Have you seen some of the tests of batteries on the net. In one case they did a shoot-out between a famous Ebay brand (FEB) 18650 and Sanyo. The FEB was labeld 4 A/H and Sanyo 2.2 A/H (not exact figures but that order). Bet you can guess which had the higher capacity. Not only that, but less V droop. If that was taken into acount, in terms of useability, the Sanyo was effectively 4x better. Also, the FEB had a much higher ESR which meant that if you had a load which requirs bursts of high current the terminal voltage dropped like a brick. Of couse, you can always get around that by slapping a big c across the battery, but that is more complication and cost, not to mention the size increase.
I stick to Eneeloop now, although you can't get them in PP3 (very troublesome things) so I use 7 day-shop versions which seem to be better than the branded types.
While on holiday in Teneriffe, a fast talking salesman pesuaded me to buy a 4,700ma/h battery for the camera on my belt. At the time the Canon batteries for the camera were 900 mA/h. I knew the spec was outlandish, but I was in a holiday mood and needed a second battery. It was a good price too.
The battery worked OK after two or three charge/discharge cycles but it was no where near 5.2 times better than the original Canon, more like 1.1x. It carried on for a year, but one day, when I was depending on it for a shoot, it died. Back at home, I opened it up. Guess what was inside- two standard sized batteries labled 1000 maH. One was dead and wouldn't recover. The other was OK, so out of curiosity, I gave it a couple of charge discharge cycles and checked the capacity- around 500 mAHr at 20mA and at capacity/10= 100ma it dropped below useable voltage straight away. Overall the camera battery was beautifully made though- much better than the Canon.
It's been 12 years now and the Canon battery is the same as it ever was.