Which is the right type of AA battery?
So many devices are powered by AA batteries, and there are so many different kinds of AA batteries, getting the right battery for a specific application can be a challenge. But read on, and you'll end up with the best solution.
Disposable AA Batteries
Using disposable batteries in general is both expensive and has a significant environmental impact. But use-once AA batteries are the right choice for some applications. If your application has one or more of the following characteristics, you should consider disposable batteries:
- You need a small amount of electricity over a long period of time, such as for a TV remote control.
- You need power some (long) time in the future, e.g. in an emergency torch you keep in your car's glove box.
- You need power in a place where there is no mains power, e.g. on your expedition to the North Pole.
Currently, disposable AA batteries are commonly available using four different technologies:
- Zinc Chloride AA Batteries
- Zinc Chloride technology is cheap and cheerful. While it stores electricity for a long time, it can only cope with low power applications, such as a basic radio. Anything more demanding will consume the battery VERY quickly. This is the cheapest version of the AA battery.
- Alkaline AA Batteries
- Alkaline technology is the ideal compromise technology. While only about twice the cost of Zinc Chloride, it will last two to five times as long in most applications. While some alkaline batteries perform better than others, most will perform to within 5% of each other.
- Oxyride AA Batteries
- Oxyride battery technology is the most recent technology discussed in this list. Launched in the UK by Panasonic in July 2005, Oxyride batteries were specifically designed for use in high-power applications such as MP3 players and digital cameras. Our tests confirm that these batteries do everything you'd expect.
- Lithium AA Batteries
- Lithium AA batteries are the top-of-the-range version. They outperform alkaline AA batteries by a factor of two or more, do much better in demanding applications (e.g. digital cameras), and work over a greater range of temperature. For your trip to the Antarctic, these are the battery of choice.
The following table gives you an idea of how the battery types compare in real applications - in relative terms. Even though we actually found these results in tests, your mileage will differ because you're unlikely to use the same make and model of device. The cost-per-shot assumes using a single battery. Again this means that the data works in relative terms - if your camera uses two batteries, you need to double the cost-per-shot.
| Type | Portable Stereo | Digital Camera | Battery Price | Cost-per-Shot |
|---|---|---|---|---|
| Zinc Chloride | ½hr | 0-7 shots | £0.89/4 | 5.56p |
| Alkaline | 2hrs | 90-110 shots | £2.09/4 | 0.55p |
| Rechargeable NiMH 2000mAh |
3hrs | ~175 shots | £4.16/4 (£0.04/4 to charge) |
0.59p (£0.006p to charge) |
| Oxyride | 3½hrs | ~440 shots | £2.99/4 | 0.17p |
| Lithium | 4½hrs | ~1300 shots | £3.76/2 | 0.14p |
Rechargeable AA Batteries
Rechargeable AA batteries are the right choice in most applications. They are both cheaper to use because you can recharge them 300-500 times rather than throw them away, and they thus help significantly reduce the waste which gets dumped in UK landfills. Some electrical trickery means that a 1.2V rated rechargeable battery will do the job of a 1.5V rated disposable battery. Rechargeable batteries are the right choice when:
- You need a lot of power over a short amount of time, such as in a digital camera.
- You have access to mains power to recharge the batteries.
- You don't need to store the power for long amounts of time.
Rechargeable batteries suffer from something called self-discharge, which means they will lose some of their charge continuously. If you leave a fully charged battery on a shelf, you'll find that its just about flat after three or four months. To get most use from rechargeable batteries, you'll thus want to charge them shortly before use. There are two common types of rechargeable AA battery:
- NiCd Rechargeable AA Batteries
- Nickel Cadmium rechargeable batteries are the proven, less expensive type. They should be used in full cycles, but are otherwise low maintenance.
- NiMH Rechargeable AA Batteries
- Nickel Metal Hydride rechargeable batteries have up to three times the capacity of NiCd batteries, making them the ideal choice for high power applications, such as digital cameras.
When selecting a rechargeable AA battery, the most important specification is the capacity. This is measured in milli-ampere-hours (mAh), and ranges from 600mAh-1100mAh for NiCd AA batteries, and from 1300mAh-2600mAh for NiMH AA batteries. A battery with double the capacity rating will typically last about twice as long in use.