Rechargeable Battery Technology

If you've ever shopped for rechargeable household batteries before, you may have noticed that there are quite a few types on the market. In truth, there are far more kinds of rechargeable batteries (for example: SUNJACK USB BATTERY CHARGER ) than those found on shelves at supermarkets and electronics stores. Lead-acid batteries power most cars, while lithium-polymer is the technology found in many cell phones.

The most common types of rechargeable AA and AAA batteries include nickel cadmium, nickel metal hydride, and lithium-ion. Rechargeable alkaline manganese batteries are also available, and are often cheaper than other options, but tend to have limited life cycles. Lithium-ion batteries, by comparison, typically last the longest of any type.

Self-discharge is the phenomenon of a battery losing its charge when not in use, and is present among all battery types, including disposables. While the rates tend to be higher among rechargeable units, there are many factors involved in the rate at which a battery loses its charge. These include age, storage temperature, and the charge capacity at which a battery is stored. While it's typically thought of in terms of shelf-life for disposable batteries, it can be represented as a percentage per month for rechargeables.

Lithium-ion batteries typically have the lowest self-discharge rate of all rechargeable battery types. They tend to lose two to three percent of their charge each month while in storage, compared to four to six percent for lead-acid and 15 to 20 percent for nickel-cadmium. Standard nickel metal hydride, or NiMH batteries, have the highest self-discharge rate at up to 30 percent per month. To combat that effect, Sanyo introduced a so-called "low self-discharge NiMH" style under their Eneloop brand in 2005. These have self-discharge rates closer to those of lithium-ion models.

If your batteries are starting to show signs of wear, the BC-700 can perform a capacity test or run them through a refresh cycle, which supposedly extends their life. While users report that it does have a tendency to declare salvageable batteries with less than .9 V as “dead”, anyone who prefers this more technical charger will probably be okay with using the “paperclip reanimation trick.” Otherwise, enthusiasts rave about the reliability and flexibility, and some have even spent years putting together FAQs with more information than the manufacturer’s own site, underscoring why we think this is a great pick.


Unlike the Lacrosse BC-700, the MH-C800S only offers two charging speeds and displays a simple three-bar battery gauge instead of detailed charging information. Plus, it costs around twice the price as our simple pick from Panasonic. We also don’t like that the charger defaults to the faster 1-A charging mode, but a clearly labeled “Soft” button will slow that down to a 500-mA rate, which you should do every time to maximize the number of recharges your batteries can take.Smart chargers with room for more than four batteries are hard to find, but if you need the extra space, we recommend the Powerex MH-C800S, which can charge any combination of eight AAs and AAAs at a time. If you use a lot of batteries, the Powerex MH-C800S is worth paying extra for. But you should only get it if you really need all eight charging slots from one outlet, since it typically costs about twice as much as the Panasonic.