Rechargeable Batteries

Beware of fake NiMH rechargeable batteries

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The research

We consider owner reviews of battery models to some extent, but only if we see an obvious pattern of failures or shortcomings. There are so many mitigating factors that go into battery performance—the charger you use, how fast you drain them, and so on—that trusting owner reviews for batteries can be perilous. But we scan through the owner reviews with the lowest ratings looking for potential defects or common failures that may be worth testing more thoroughly.

Mainly we use the following criteria to determine which models are worth testing:. The more energy a battery can hold when charged, the less often you need to charge it. Most trustworthy companies right now make AA batteries around 2, mAh. The batteries we consider are rated to last 1, to 2, cycles, though every time you cycle a battery—charge and discharge it—it dies a little inside.

Putting the macabre metaphors aside, that means that if you charge a battery hundreds of times, it will have a lower capacity than when you first bought it. Even when charging once a month, being able to reuse our picks for five years would bring your cost per charge down to less than a nickel, which makes rechargeables worth the high initial price compared with disposable alkaline batteries.

To test for capacity, we use four batteries from each brand. As soon as we unpack them, we drain them to zero. Then we charge and discharge them three times and average each set of results. That gives us an average of 12 discharge measurements, which we compare with the stated capacity. For AA batteries, we charge at mA and discharge at 1, mA. For AAA batteries, which have less capacity and should be charged and discharged more slowly, we move down to mA for both steps.

Each brand we test for capacity also goes through our tests of how well it holds a charge after repeated cycling. Using our average capacity test as a baseline, we cycle each battery nearly 50 times to see how it holds up to repeated charging and discharging. We know that rechargeables have a bad reputation for losing their mojo a bit too quickly, and this test is a good way to stress the batteries even more than you would at home.

After 48 cycles, we do the capacity tests again.

Losing between 1 and 4 percent a month, brand-name batteries still have more of a charge after six months sitting on a shelf than a discount, alkaline disposable battery has out of the box. Over longer stretches, though, a percentage point here and there can start to add up, so the lower the self-discharge rate, the better a battery is for long-term storage such as in emergency kits. For AA batteries, we tested eight brands in new, single-battery Coast flashlights.

We sealed each one into a cardboard box with a video camera to monitor the light output over time.

We recorded the time until each flashlight went out completely, but we also took into account batteries that dimmed prematurely. We loaded four headlamps—one each for AmazonBasics, Energizer, Eneloop, and Duracell batteries—and set about draining them completely. Because it would take too long to stand around and wait for the lamps to run down, we strapped our headlamps to some stand-ins watermelons and let a camera observe them slowly dimming as the night wore on. As in our capacity and cycle tests, the AAA batteries all performed roughly the same, so we called this test a tie as well, and snacked on watermelon for a few days.

Nothing drains a battery quicker than an electric motor, so we tried three top-performing AA brands—Eneloop, Energizer, and Powerex—in a high-stress situation. Trackside has an indoor RC race track that hosts national competitions in addition to its normal open-track practices. These cars are serious, regularly going 40 mph, with brushless motors powered by high-quality lithium-ion battery packs—far too fancy for our purposes.

Instead, Tennies soldered our sample batteries into a pack with high enough voltage to run our test cars around the track. Our naked test car, loaded up with the soldered Energizer battery pack. Since he knew all the turns and ramps on the track, we asked Jamie Tennies to drive our test car with each of our battery packs—around and around and around, for more laps than we bothered to count.

We measured our results with a stopwatch. To keep the driving style roughly the same, Tennies used each pack in turn to drive the same car around the track, and we stopped the time on our stopwatch when the car lacked enough power to clear one of the track hills. Five minutes turned to six, and at 10 minutes in, we started getting nervous about exactly how long our experiment would run.

Beware of fake NiMH rechargeable batteries

In the end, our little AA battery packs raced around the track for between 11 and 15 minutes each. Not surprisingly, the Powerex batteries, rated for roughly 25 percent more capacity, lasted the longest. Like our other picks and major competitors, both battery lines are made in Japan.

As far as we know, only one factory in that country produces this kind of battery, so at the very least both lines are coming from the same source but with potentially different materials that can affect the final performance. Since the Eneloop Pro batteries are supposed to be higher capacity and capable of keeping up with high-power, repetitive demands such as from professional camera flashes, we figured we had the ideal test scenario to compare their performance. We opened new packages of Eneloop Pro and Ladda batteries, drained them once, and then charged them to full before putting them in two brand-new hot-shoe camera flashes.

With a timer going, we strobed the flash once a second for three seconds, let it rest for two seconds, and then repeated. When our cycle was complete, our light sensor produced a graph showing how fast the flash recycled, how many times it was able to strobe, and whether it strobed at full intensity.

The Eneloop Pro batteries kept up with 44 flashes while the Ladda batteries stumbled on a few activations and managed In addition to buying them online, you can find Energizer Recharge Universal batteries in stores, including major home-goods retailers, big-box hardware stores, and electronics stores. Capacity ratings of brand-name batteries range from around 1, to 2, mAh, with Energizer Recharge Universal coming in at 2, mAh.

In all of our tests over three years, Energizer rechargeables have consistently ranked at or near the top of the results. When we tested the run time of our batteries in Coast flashlights, the Energizer batteries lasted about as long as those with higher capacity ratings.

Further reading

We recommend the Powerex MH-CS if you use a lot of batteries and want a way to charge more than four of them simultaneously. The Powerex has two charging speeds and displays the status of each battery, and it can accept any combination of AA and AAA batteries. But since it costs about twice as much as our top pick, we recommend it only for people who actually need the extra capacity.

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 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. The Lacrosse BC 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.

But while the Eneloop charger does everything behind the scenes, the BC 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. If your batteries are starting to show signs of wear, the BC 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.

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-CS , which can charge any combination of eight AAs and AAAs at a time. 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.

Unlike the Lacrosse BC, the MH-CS 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. No matter what charger you use, you can follow a few simple rules to keep your batteries in the best condition possible. 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.

Instead, take them off within a day of charging. By driving a current through the battery in the reverse direction, the equilibrium can be shifted back towards the original reactants.

Rechargeable battery

Different batteries rely on different chemical reactions. Some reactions are readily reversible, some are not. The reactions used in most alkaline batteries fall into the latter category. In particular, the metallic zinc generated by driving a reverse current through the cell will generally not return to its original location in the cell, and may form crystals that damage the separator layer between battery anode and electrolyte. The rechargeable alkaline battery was, at one time, cheaper than other rechargeable types.

The Best Rechargeable Battery Charger (for AA and AAA Batteries)

They are of dry-cell construction, completely sealed and not requiring maintenance. Cells have a limited cycle life, which is affected by deep discharge; the first cycle gives the greatest capacity, and if deeply discharged a cell may only provide 20 cycles.

The available energy on each cycle decreases. Like primary alkaline cells, they have a relatively high internal resistance, making them unsuitable for high discharge current for example, discharging their full capacity in one hour. Unlike rechargeable alkaline batteries, NiMH batteries can endure anywhere from a few hundred to a thousand or more deep discharge cycles, resulting in a long useful life; their limitation is now more usually by age rather than cycles. This makes them well suited for high current capacity applications. Rechargeable alkaline batteries are developed from primary alkaline batteries , designed to resist leakage that a recharge could cause, so they can be safely recharged many times.

According to the websites of EnviroCell [8] and PureEnergy and according to old Rayovac packaging, these manufacturers' rechargeable alkaline batteries have no mercury or cadmium. From Wikipedia, the free encyclopedia. This article has multiple issues. Please help improve it or discuss these issues on the talk page. Learn how and when to remove these template messages. This article contains content that is written like an advertisement. Please help improve it by removing promotional content and inappropriate external links , and by adding encyclopedic content written from a neutral point of view.

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