Why Go Rechargeable? Part 5
Max Power: Take your rechargeable use to the next level

Erica A.

Wednesday, November 05, 2008

Low self-discharge batteries

If it’s been a while since you looked at rechargeables, you may remember wondering why the batteries didn’t come pre-charged. The reason is that until recently, most rechargeables lost their charge quickly when not in use. Stored on the shelf, a standard NiMH battery loses 25 percent of its power by month. Inactive NiCd batteries lose 10 percent of their power in the first 24 hours, then lose 10 percent a month.

But three years ago, manufacturer Sanyo introduced low self-discharge standard size batteries under the brand Eneloop. (How’d they do it? By improving the cathode structure and the separator. You can read a technical explanation from Sanyo here.)

In addition to their increased shelf life, this battery technology lasts through many more charge cycles than standard NiMH and NiCd rechargeables. While standard NiMHs last up to 500 charges,

The technology soon spread through the industry, and today all of the major battery manufacturers offer low self-discharge batteries.

What is mAh?

Many batteries come with a label like “2500 mAh.” The acronym mAh stands for milliampere-hour, and this number means the capacity of the battery. A miliamp is one thousandth of an ampere, or amp. (Engineer’s Edge has a good technical explanation of battery capacity). What do mAhs mean for your AAs? BatterySavers.com explains:

If you think of a battery as a small fuel storage tank, which in a sense it is, mAh is a measure of how much "fuel" the battery holds. (This is roughly comparable to using gallons to measure how much fuel a gas tank can hold. The more gallons of capacity, the more fuel the tank can hold.) With a battery the higher the mAh rating, the more electrical energy it can store.

Why should you care? Some devices are like Priuses, putt-putting along slowly and evenly, with occasional accelerations. Others are like Ferraris, demanding more power and demanding it now. (Digital cameras are often in this category.) It’s important to note. A higher battery capacity will NOT overload the power of the device.

If you’re using a high-drain device—and you probably already know if you are—than mAh matters more. If your batteries have a short shelf life, a higher capacity will keep them alive longer.

Michael Bluejay has a in-depth look at electricity usage around the house here. It talks about AC (wall plug electricity) rather than DC (battery), but it’s got a lot of useful information on measuring electrical demand.

Recap

Here’s the least you need to know about rechargeable batteries:

Rechargeables can be used between 500 and 1000 times.
Rechargeables are better than ever thanks to the development of low self-discharge rechargeables.
It costs about 25 cents a year to recharge 120 AA batteries. (Source: The Simple Dollar).
Rechargeable batteries are up to 32 times greener than disposable alkalines. (Source: Uniross).

The verdict: what are you waiting for? Check out AtBatt’s rechargeable batteries now.

Part 1: Why Go Rechargeables: A Mini Blog Series

Part 2: The Different Kinds of Rechargeables

Part 3: Save money in the long run

Part 4: Heavy metal: Rechargeables and the environment

Part 5: Max Power: Take your rechargeable use to the next level

Why Go Rechargeable? Part 5 Max Power: Take your rechargeable use to the next level