A Complete Guide to AA Batteries

The advantage of rechargeable AA battery packs is that they behave much like a single cell in terms of swapping them in and out. For devices requiring multiple batteries to power on, this is much more convenient than having to remove each individual cell one by one when you need to charge or replace them.

Good quality rechargeable battery packs are usually assembled such that all the individual AA cells in the pack are functionally identical, reasonably balanced, and can be charged and discharged at similar rates to one another over their active lifetimes. This is better and safer for both the batteries themselves, and the long-term health of the devices they’re powering.

When various batteries working together are unable to discharge at equal or consistent rates, some cells can end up being placed under excessive workloads as they struggle to compensate for weaker performers. Combining loose or non-identical rechargeable AA batteries - particularly of different ages and active cycle capacities - in a single device can, therefore, lead to power or stability issues, which is why battery packs are generally a far better option in this scenario.

We’ve touched on the dangers of mistreating certain high-drain rechargeables - particularly li-ion batteries - in previous sections, but what about regular disposable AA batteries? Can they explode or rupture in dangerous ways? Well, while it’s very rare indeed for AA batteries to explode in typical day-to-day use, ruptures or even small explosions aren’t impossible.

When a standard AA alkaline battery is inserted into a circuit and starts to deliver power, there’s actually a chemical reaction taking place within the cell that produces small amounts of hydrogen gas. Most AA batteries from quality brands will be vented to allow for this. However, the fact that this gas is being generated under pressure inside a sealed metal chamber means that, should a product malfunction or be placed in a situation it’s not equipped to handle, issues can occur.

In most cases an AA battery will only rupture violently if it’s inserted in the wrong direction, exposed to high operating or storage temperatures, mixed with other cells of the wrong type or very different capacities/charge levels, or if a user attempts to (re)charge a cell that isn’t designed to do so.

Even outside of these scenarios, though, a very small number of substandard or faulty cells can potentially burst due to less clear-cut misuses. One of the more common causes of leaking or rupture in alkaline AA batteries is running a fresh cell alongside a heavily drained one - on rare occasions, this can end up effectively reversing the polarity on the drained cell, which can quickly cause problems.

Yes, AA batteries are allowed on planes, although there are some caveats and best practices you should be aware of:

• Dry-cell batteries, which include alkaline, lithium and NiMH rechargeable AA batteries, are allowed in carry-on luggage (both inside devices and as spares)
• With the exception of spare lithium AA batteries, which must only be carried on board, all of the above are also allowed in checked baggage
• However, it’s generally not recommended to put spare batteries in checked baggage if you can possibly avoid it - it might seem counterintuitive, but in the unlikely event of a problem, you’re far safer having them with you in your carry-on luggage where they can be accessed by staff trained to deal with such issues
• All spare batteries carried outside devices should be packed in a protective plastic case, individual plastic bags, or at the very least have their contacts taped over for the duration of air travel
• Never carry loose batteries in bags containing other metal objects (including coins, paper clips, zips etc), as this can cause them to short-circuit and become dangerously hot
• Consult your airline for advice regarding any spare rechargeable Li-ion batteries - these are generally allowed as carry-on, but are often subject to strict size limits

Many AA batteries today boast impressively long shelf-lives, which is especially useful given that you can often enjoy considerable discounts when buying in bulk or larger multipacks. However, achieving optimal shelf-life for most AA cells depends on proper care and storage.

Tips to be mindful of when considering how to store AA batteries long-term include:

• Keep them out of the reach of children
• Ensure they’re stored in a cool and dry environment (room temperature or below)
• Where possible, keep them in their original packaging until ready for use - this not only helps to protect unused cells, but also differentiates them from older or partially drained units
• Don’t store batteries inside devices if you’re not going to be using them for a long time
• If you’re storing a mixture of brand new and partially used batteries, keep them separate and clearly labelled
• Make sure they’re unable to short circuit through direct contact with any other metal items - use a plastic battery storage box, individual plastic bags, or put tape over the terminals
• Periodically test and top-up rechargeable AA batteries, if they’re going to be stored for a long time, as letting them fully discharge in storage, can seriously deplete their capacity
• Never disassemble, puncture, crush or burn batteries of any kind
• Never store rechargeable batteries inside a charger, and never attempt to recharge a battery that’s not designed to do so

Batteries eventually leaking or corroding is a relatively common occurrence, especially familiar with alkaline AA cells if they’re left unattended for long enough. In short, the reason alkaline batteries leak is that they’re continually self-discharging in tiny increments, even when not in use.

Because the discharging process in alkaline batteries creates small amounts of hydrogen gas, pressure gradually builds within the sealed casing of the battery, and in time a small amount of material from inside the cell will often be ejected under this mounting pressure. This material is usually corrosive and should be removed from the skin immediately, then cleaned away from electrical components as soon as possible after that.

The best way to avoid leakage is to regularly replace older batteries, take note of the battery storage best practices outlined in the section above, and to switch to lithium or rechargeable cells for long-term storage if you only need to power a device very occasionally.

As a quick point of note here, it’s actually a popular misconception that all batteries necessarily need to be recycled. Most do, and all should be - but it’s not absolutely essential with every type.

While nearly all rechargeable batteries do indeed need to be sent for recycling, it is in fact perfectly safe to throw out single-use alkaline batteries along with your other household waste. If you insist on doing so, always ensure they’re not likely to short-circuit on any other metal items such as cans and foil when disposing of them.

However, just because you can, it doesn’t mean you ought to: in reality, nearly all AA batteries (including basic alkaline disposables) contain a significant proportion of materials that, wherever feasible, should always be recycled for the long-term benefit of the environment.

When recycling batteries, they aren’t generally considered suitable for disposal in domestic collection bins. The easiest way to recycle any type of AA battery is generally to return it to the point of purchase next time you need to buy more: nearly everywhere that sells AA batteries will also have a collection point for old ones. Failing this, your local collection network will generally feature a drop-off facility at the nearest depot, and often in a number of other locations around the community.