After six hours of looking over specifications and comparing reviews, we found three different chargers that will keep your batteries in top condition with differing degrees of input. The Panasonic Advanced Individual NiMH Battery Charger (for example: SUNJACK USB BATTERY CHARGER ) is the best pick for most people that want reliable charging without much fuss—it even includes four Eneloop AA batteries, which would otherwise set you back about $12 on their own. If you do want to take the time to measure and maximize your batteries’ performance (and are willing to pay about twice as much for that ability), the Lacrosse BC-700 allows for more in-depth monitoring and management without spending too much. And if four slots isn’t enough, the Powerex MH-C800S can charge up to eight batteries at once while giving you some basic feedback on their progress. All three models offer independent charging slots (so you don’t have to charge them in pairs like on older chargers) and more accurate monitoring and charging.
No matter what charger you use, you can follow a few simple rules to keep your batteries in the best condition possible. First, if your charger has selectable current, choose the option that’s about 500 mA (.5 A) or less for AAs and about 200 mA (.2 A) or less for AAAs–sometimes labeled “slow” or “gentle” charging. Charging at higher speeds can reduce the number of times you’ll be able to recharge your batteries. Overcharging batteries can also reduce their capacity. Even though our recommended chargers are designed to prevent overcharging (they detect charge states by utilizing Negative Delta V detection and pulse charging) and cut off current when batteries are full, small leaks and trickle charges over long periods of time may still cause cumulative damage. So don’t store your batteries on the charger. Instead, take them off within a day of charging.
If you want simple charging and don’t care to monitor your battery’s capacity down to the mAh, your best option is the Panasonic Advanced Individual NiMH Battery Charger (BQ-CC17ABA). It has four individually managed charging positions that let you mix any combination of AA and AAA batteries and doesn’t require two batteries at a time like comparably priced offerings from Duracell and Energizer or many older chargers. It’s dead simple to use: just put your batteries in and wait until the charging light turns off.
Underneath the hood, it uses the more sophisticated techniques of expensive chargers to avoid undercharged batteries that discharge quickly or overcharged batteries that will end up with a shorter service life (and will become unusable sooner). It will charge your batteries at a gentle 300 mA to preserve capacity and will automatically terminate the charge when it detects that your batteries are full–about seven hours for a typical NiMH AA battery.
Since prices change frequently, it’s worth comparing the stand-alone charger to the charger with four batteries to see which one is the better deal.
The Lacrosse BC-700 will help anyone that wants to actively manage their batteries squeeze out every drop of power without adding superfluous features and breaking the bank like the top-of-the-line Powerex WizardOne—but it still costs about twice as much as the Panasonic charger. The BC-700 is based on the same pulsed charging and Negative Delta V detection as the Panasonic above, so you know it’s an accurate, automatic charger. But while the Eneloop charger does everything behind the scenes, the BC-700 displays the status of each battery position on a small LCD and allows you to independently select between three charging speeds as well as a variety of testing and maintenance modes. For most people, the repeated button presses needed to sort through these features will just make rechargeable batteries seem like a chore, but the work can help eke out slightly longer lives and marginally increased capacity if you’re willing to invest the time.