Get more out of your batteries

Rechargeable batteries seem like a great idea; they don't cost a lot more and you can reuse them up to 1000 times. The savings are obvious.

So why do so many people migrate back to one-time-only batteries? Maybe I'm just the guy to answer that question.

In 2003 I bought a cordless mouse and figured the two AAs it needed wouldn't last long, so I used rechargeables in it for about a year-and-a-half. They'd last anywhere from a month to six weeks between charges.

I got so fed up with recharging, I bought a set of conventional alkalines to see how long they'd go. Eighteen months. Rechargeables? Forget them.

What ignorance this was on my part. Using rechargeables in a mouse was dumb. They're made for high-drain devices such as cameras, portable DVD players, toys and computers. Compounding this, I'd bought the cheap 900 milliamp-hour (mAh) variety.

That mAh number is a guide to how much power the battery stores, thus how long it lasts between charges, and 900 is about as low as you'll find these days, although I have seen 850s. Pay more and they go as high as 2650 mAh. Had I spent a bit extra, I would have got longer life.

But really, any sort of rechargeable was wrong here because rechargeables self-discharge. To put that in English, they go flat. If you charge up a couple and put them in your camera bag for the day, they could well be flat as pancakes after three months when the ones in the camera run out. Certainly after six.

The exceptions here are ready-to-use rechargeables that are sold fully charged. These retain about 80 per cent charge a year after charging. They're not a great deal more expensive than standard rechargeables, either.

But while they'd extend the life of my mouse even further, they're still best in high-drain devices, just like all other rechargeables. For low-drain items such as smoke detectors, remote controls, the back-up batteries in your clock radio and, yep, cordless mouses, stick with conventional batteries.

If, like me, you swore off rechargeables years ago, you need to know that they've come a long way since. Nickel-cadmiums have all but disappeared and while lithium-ion batteries are turning up in lots of phones, organisers and computers, as far as your AAAs, AAs and other common types go, nickel-metal hydrides (NiMHs) are all you're likely to find. And they're so clever now that memory effect is no longer an issue.

This used to be the killer with rechargeables. If you weren't disciplined in using the charger they'd become useless fast. But current NiMHs are so robust you can charge them whenever you want without damage, although if you get into the habit of running them until they drop, it may shorten their life. That said, the odd deep cycle is good for them.

When starting out, the best idea is to buy a set of batteries packaged with a charger so you know the batteries and charger match. The next best idea is to do the initial charge as per the instructions.

You get what you pay for. More expensive chargers protect the batteries from their two big enemies, over-charging and over-heating. And they're not just damaged by heat generated in charging; leaving them in a hot car will also shorten their lives.

Taking charge

Mark Tysoe is an unusual man; he gets excited about batteries.

Using rechargeable batteries to their full potential in place of conventional one-time-only numbers is, he says, 30 times kinder to the air and 20 times nicer in terms of global warming. And you're having 23 times less impact on non-renewable resources.

Mr Tysoe is the national business manager for Varta, one of the world's big names in batteries, and he's celebrating the death of the nicad, an environmental Darth Vader which is banned in lots of countries, by launching his company's environmental masterstroke.

It's a A$60 (NZ$77) solar-powered charger that handles AAs, iPods and phones. An hour of sunshine can give you 20 minutes' talk time on your mobile or 50 minutes' music from an iPod. And if it happens to be dark, it can charge via a USB connection.

The charger comes with two rechargeable AAs.

- © Fairfax NZ News