Eneloop Pro AA
Do you want to buy a new battery charger? Whether it's your first time buying a charger or you're replacing an old one, it’s worth knowing what extra features are worth paying for. Below, we explain what you need to know about battery chargers - including how to get the best from your charger.
A battery charger with lots of features, such as a charge indicator, super-fast charging or the ability to charge 9V batteries, might be tempting as it covers all possibilities. But you’ll pay more for these extras, so it’s worth thinking about whether they’ll be useful to you.
Once you’ve worked out what type of battery charger you want, make sure you buy the best rechargeable batteries to put in it. The best AA rechargeable batteries last nearly eight hours on a single charge and won't leak away their charge between uses. However, the worst AAA rechargeable batteries we've tested lose nearly 20% of their charge if you don't use them for 50 days.
Smart battery chargers, also known as delta-V chargers, monitor the voltage levels in each battery and stop charging (or switch to a low trickle-charge setting) when they’re full. Smart battery chargers are usually the best choice for keeping rechargeable batteries in good shape, as they prevent overcharging, which can reduce battery lifetime.
These push a low ‘trickle’ charge through batteries for a long period of time. Some have timers, so they turn off automatically after a set period of time. This won’t necessarily prevent overcharging or undercharging, though. This is because the time will vary depending on the battery’s capacity, chemistry and age, among other factors.
Trickle chargers are useful if your rechargeable batteries aren’t ‘low self-discharge’ models (which have technology to stop them leaking away their charge when not in use). Ideally, the trickle charge is equal to the charge that the battery leaks away naturally, so they’re kept fully topped up - ready for when you want to use them. However, keeping them constantly topped up also increases the likelihood of overcharging.
If a battery charger isn't marked as a smart charger or trickle charger, it’s likely to be a more basic model that pumps a constant electrical current through batteries until you unplug it. These models are often much cheaper but it can be hard to tell when batteries are fully charged - and the charger won’t stop charging them when they are. So you risk overcharging, which can cause long-term damage. Excess energy can cause batteries to get hot. However, undercharge them, and they’ll run flat faster.
The type of battery charger that's best for you will depend on how you plan to charge your batteries, and how much you want to spend. Can you plan ahead to recharge your batteries? Or will you need a quick turnaround when they’re flat? Manufacturers claim that the fastest battery chargers can charge in just 15 minutes, but they usually cost more. The slowest are often cheaper, but need to be left overnight. Our measure how long different brands take to charge.
Battery charging technology is constantly evolving, and many smart chargers are claimed to charge batteries in under an hour. The fastest models should be able to charge in 15 minutes – which is convenient, as you don’t need to think about charging your batteries before you want to use them. They tend to be pricier than other battery chargers, however.
Manufacturers often state the expected charging time on their battery chargers – for example, both Duracell and Energizer sell a ‘one hour’ charger, among other models. Exactly how long it will take depends on the capacity of your rechargeable batteries. In the same charger, higher-capacity batteries will take longer to charge than lower-capacity ones. Other chargers are designed to be left charging overnight – some have auto shut-off functions after certain time periods to minimise overcharging.
As you choose your battery charger, you also need to think about:
Smart or trickle charger? Should you buy superfast? Do you really need a charge indicator? We asked hundreds of Which? members what is important and useful to them about their battery charger. Read the tips below to help choose the best for you – and avoid purchasing a dud.
The most important factors to consider when buying a new battery charger:
(Based on a survey of 1,346 Which? members with battery chargers in February 2016)
Top-of-the-range smart chargers can cost from around £25 to £40. Combined with the cost of the rechargeable batteries (which can be around £12 for a four-pack), getting started can be a small investment. But the cheapest chargers we’ve seen cost less than £10, so you can still use rechargeable batteries on a budget.
When we surveyed Which? members in February 2016 about battery chargers, they told us they spent, on average, £13.40 on a battery charger. A fifth (21%) spent less than £10, while just 9% spent more than £20. Use this as a guide to make sure you don’t pay over the odds.
If you’re shopping in a supermarket, look out for offers on battery chargers; we’ve seen up to one third off a charger with AA and AAA batteries included in major supermarkets.
Different capacities of rechargeable batteries (indicated in mAh or milliamp hours, printed on the packaging) shouldn’t be charged together. This is because smaller cells could be overcharged and larger ones not fully charged in the same session, which can damage batteries over time. Batteries with different chemistries - such as nickel-metal hydride (NiMH) or Nickel Cadmium (NiCad) – shouldn't be recharged together either.
Manufacturers often recommend that their batteries are charged best by the same brand's battery chargers. This is because they can adapt how the charger works to suit their batteries. That doesn’t mean you won’t be able to charge batteries from different brands in your charger, though. We tried this out with five battery chargers and found they didn’t have any problems charging generic batteries, but were sometimes slower to charge than with batteries of the same brand as the charger.
Some battery chargers are claimed to be able to recharge disposable alkaline batteries. We recommend you don’t bother with these. We tested two (the Deluxe Battery Wizard for alkaline and zinc-carbon batteries, and another battery charger for disposable alkaline batteries) with Energizer alkaline batteries. After two cycles, on average, we found battery capacity had dropped to just 10% of its original, with huge variations. With such unreliable results, they’re not a gadget worth spending money on.