Sanyo Eneloop Rechargeable Batteries

Rechargeable batteries are a great idea in theory, but reality is usually different. Short life between charging and dead batteries when you really need them are two common problems, and that’s why throw-away alkaline cells remain so popular. There is, however, one particular type of rechargeable battery that’s different enough to have made me swear off throw-away batteries forever. It’s called Eneloop, and it’s the best rechargeable AA and AAA consumer battery I’ve seen in 20 years of testing.

Poor shelf life has been the main problem with standard rechargeable batteries ever since they first came out in the early 1970s. Put that flashlight, toy or digital camera on the shelf for several months and you’ll find that standard nickel cadmium or nickel metal hydride AA rechargeables are either dead or weak at the moment you really need them. Depending on the battery chemistry involved, standard rechargeables can lose as much as 20% of their charge each month just sitting there. Who wants to take the time to put batteries in the charger and wait for them to revive when you need light, music or your kids are eager to play with a toy? Disposable alkaline batteries, on the other hand, hold a nearly full charge for years, delivering good performance at a moments notice. Alkalines also hold a lot of energy, too, delivering longer run times than most rechargeables. This is the reason why people keep paying big bucks for alkalines and putting up with the guilt of tossing them out.

Technically speaking, Eneloop batteries are based on nickel metal hydride chemistry, like many other lack-luster rechargeable cells. That’s why I didn’t pay much attention to them the last time I went searching to see if any great new rechargeable battery technology had appeared on the market. But when a photographer friend of mine couldn’t say enough about how well Eneloops perform in his flash equipment, I gave them a try. He was right.

Somehow Sanyo has figured out a way to enable their nickel metal hydride Eneloops to hold a charge for a long time in storage. This means they come out of the package charged to at least 85% of their capacity and ready to use. Even after sitting on a shelf for six months after receiving a full charge, Eneloops still retain 90% of full capacity. Regular nickel metal hydride rechargeables would be completely flat (and poised to cause frustration) after this amount of storage time.

Long shelf life is one thing, but energy capacity is another. It’s the battery equivalent of the size of gas tank in your car. The larger the amount of electricity stored in the battery, the longer it can operate equipment between charges, the more you’ll like the battery. Milliamp hour rating is the simplest way that battery capacity is measured, and a brand new AA alkaline cell typically comes from the factory with about 2500 milliamp hours of energy stored in them. The most common type of Eneloop AA cells have a 2000 milliamp hour rating, and although this is less than some alkalines, in practice there’s more to it than these numbers. The discharge pattern of Eneloops allow them to perform better than their numbers would suggest in high drain applications, especially involving flash equipment and digital cameras. Excellent performance operating a flash is the application that got my photographer friend raving, but there are other uses, too. Reliable, high-energy cells have also allowed Sanyo to develop effective, rechargeable hand warmers – a product that wouldn’t be practical with any kind of disposable cell.

Sanyo has opted to focus on AA and AAA cells for the Canadian market, feeling that we wouldn’t want to pay for the larger C and D Eneloops available in other parts of the world. This may be true, but only because most of us don’t know what really good rechargeables are like. And while it’s often difficult to find the best products in an ocean of marketplace mediocrity, as far as rechargeable AA and AAAs go, I don’t think you’ll find anything better right now than Eneloops.