After 6 years of researching and writing about AA and AAA rechargeable batteries and chargers, this site continues to have the same basic advice:
Use pre-charged, low self-discharge (LSD) batteries for AA and AAA battery needs. When used with a quality charger, LSD batteries offer the best combination of long-term cost-effectiveness, quality, durability, and environmental sustainability. Once you’ve tried LSD batteries with a good charger and realize how good they are, you’ll end up using them for the vast majority of devices that require AA or AAA batteries.
If you prefer to skip the details, click to the Just Tell Me What to Buy section of this article. If you prefer to understand what you’re buying, read on.
This guide is a 2017-2018 update on AA and AAA rechargeable batteries and chargers. It will be maintained and updated to stay current through early 2019. The technology and products associated with AA batteries and charges change slowly, so this will be easy.
In addition to this guide written by me, Jim Hyman will continue to test batteries and write articles for FilterJoe. Jim has been supplied with a few chargers to test by DC Workshop. When Jim’s testing reveals new information, appropriate changes will be made to this guide.
As you can see from the following table of contents, I cover LSD batteries, budget chargers, premium chargers, storage, and other AAA and AA-battery-related topics. I recommend specific products for different budgets and needs. I also provide a Just Tell Me What to Buy section for those who just want to cut to the chase.
- Just Tell Me What to Buy
- Why LSD Batteries Blow Away the Competition
- History of LSD Batteries Since 2005
- The LSD trade-off: Higher capacity means fewer recharges
- Recommended LSD Battery Brands (and Country of Choice: Japan)
- What to Look for in a Budget Charger
- Extra Features to Look for in Premium Chargers
- Recommended Budget AA/AAA Chargers
- Recommended Premium AA/AAA Chargers
- Storing AA and AAA batteries
- When to Use Alkaline or Lithium Batteries (hint: rarely)
- Concluding Remarks
Do you own a cast iron skillet? If so, how often have you had to replace it? If you treat it well, the answer is never.
Well, low self-discharge (LSD) batteries are the cast-iron skillet of the battery world . . . but even better because there aren’t any drawbacks other than the higher up-front cost.
There are so many headlines about breakthrough battery technologies that will be the wave of the future for autos, smart phones, or storing electricity generated by solar power. But U.S. consumers still spend over $4 billion annually on mundane AA and AAA batteries to power remote controls, flashlights, digital cameras (and DLSR flash attachments), book lights, toys for kids, and many other devices. Despite this sizable market, Sanyo’s Eneloop breakthrough that occurred in 2005 continues to receive scant attention.
Toys are what inspired me to start learning about AA batteries. Something just seemed wrong about buying dozens of Alkaline batteries per year to power my toddler’s toys. Something seemed even more wrong when my rechargeable (high discharge) NiMH batteries could not power toys after 3 or 4 months despite not being used. Thankfully, I discovered Eneloop batteries when my son was 5 years old. I soon switched our family to using exclusively LSD batteries such as Eneloop, along with a good battery charger.
A year, and a bunch of research later, I wrote my first article on LSD batteries:
Since then I’ve written many more articles that have been collectively viewed by over 100,000 visitors. Though much has stayed the same since that article was written, numerous battery chargers have come and gone, and Eneloop has spawned many competitors for LSD batteries. Are these LSD competitors as good as Eneloop?
Some have tried to answer this question by extensively testing many different brands of batteries. They have generally found that LSD batteries produced in Japan don’t differ all that much from each other (with the exception of the capacity/longevity trade-off). And that’s the key: Japan.
The original Eneloop batteries were designed and developed by a battery factory in Takasaki, Japan. That factory and the Eneloop brand were both owned by Sanyo through 2009 but since then, Panasonic has owned the Eneloop brand name, while Fujitsu has owned the factory and all the intellectual property associated with the manufacture of LSD batteries, as part of its FDK subsidiary. In other words:
The leader in the AA/AAA battery field is not Eneloop or any other brand, but the Fujitsu NiMH battery factory located in Takasaki which makes batteries for many brands.
I discussed this at length in a section of last year’s battery update so I won’t repeat all that information here. All you need to know as a consumer when purchasing LSD batteries is to look for the following words:
Made in Japan
LSD batteries made in China are generally less expensive than those made in Japan. However, given that these batteries last for decades, I recommend purchasing only the highest quality Japan-sourced LSD batteries from reputable U.S. retailers such as Amazon, NewEgg, and Costco. There are surely other reliable retailers but these are three that I’m confident will sell batteries that are genuinely from Japan, if that is what is claimed on the packaging (note: by Amazon I mean direct from Amazon. Buying from a third-party merchant is not going to guarantee that you actually receive LSD batteries made in Japan).
Fujitsu is a brand that you can count on to always come from Japan. So far, Eneloops in North America, Europe, and Japan also come from that same Takasaki factory. Many other brands source LSD batteries from Japan, but some brands also source LSD batteries from China. If you do buy one of these other brands, be sure to inspect the packaging and the batteries themselves to be sure they are sourced from Japan.
Just Tell Me What to Buy
Determining which LSD brands to buy and how to properly take care of AA or AAA batteries does not change much from year to year. Generally, I suggest products to match a given set of criteria, not recommend a one-size-fits-all category winner. But in this section I do try to simplify as much as possible.
If you are new to LSD batteries, I strongly recommend buying a combination pack to get started. I suggest the following inexpensive package, which includes 8 AA and 2 AAA Eneloop batteries, as well as a compact yet capable charger:
If you already have a good charger, then you only need to buy batteries. Given that Fujitsu owns the factory in Japan that makes the best LSD factory in the world, you can always count on them for high quality AA batteries:
The Eneloop AAA batteries seem to be much more readily available than the Fujitsu AAA:
You can get a higher capacity for a higher price and reduced number of recharges:
For those who want it, the rest of this article has much more detail on various brands of batteries and features of different chargers. For example, there are batteries on the market with higher capacity at the expense of longevity. There are also more expensive chargers for those who want additional features beyond simply charging their batteries.
Why LSD Batteries Blow Away the Competition
Different battery chemistries have been explained on this site several times, most thoroughly in the original article: Best AA Batteries You Never Heard of.
The two classifications of AA/AAA batteries are single use (dispose after one use), and rechargeable (reusable many times by recharging after the battery is depleted).
Single-use batteries battery chemistries over the last few decades have varied. However, over the last 5 years, by far the most popular chemistries for AA/AAA batteries have been Alkaline and Lithium.
Alkaline batteries are popular due to low cost, simplicity, higher initial voltage (when close to fully charged), and long shelf life (retains nearly full charge for many years). Alkaline AA batteries can be had for as little as 25 cents each when purchased in bulk, though that cost can be over $1.00/battery when purchased in small quantities.
However, the cost of Alkaline batteries is not so low considering how often they need to be replaced, even at 25 cents per battery. For example:
Digital cameras are a common use for AA batteries. A frequent picture taker may go through 4 batteries per month, which means 48 batteries per year and $11.50 if purchased in bulk 48-packs. Sounds like a great deal, right?
However, you can purchase a battery/charger pack that includes 4 low self-discharge rechargeable Eneloop AA NiMH batteries and a decent charger for around $16. After just two years, the Eneloop bundle comes out ahead. Rechargeable batteries do cost about 10-15 cents of electricity per year to charge, so figure about $16.25 total spent after 2 years, versus $23 for bulk-purchased Alkaline batteries. As you continue to use the Eneloop LSD batteries, the savings pile up over the years. Eneloop batteries recharge 2100 times before they can no longer hold much charge, according to Panasonic. I strongly suspect that ideal storage and usage conditions are required to achieve 2100 recharges, but even if it’s only 1000 recharges, that would last over 80 years for the digital camera that fully uses 4 batteries each month.
But that’s not the whole story. Alkaline batteries do not provide power efficiently in digital cameras, for reasons too technical to get into here (for technical detail, see Loading Characteristics on Primary and Secondary Batteries). They drain much faster when used in “high drain” devices such as cameras than NiMH or Lithium chemistries, so therefore you’ll need to change LSD batteries less frequently than you would with single-use Alkaline batteries.
Alkaline batteries are well suited to low-drain devices such as remote controls or game controls, which do use the Alkaline batteries efficiently. However, I still avoid using Alkaline. In most applications, LSD batteries perform the same or better, at a lower cost over time.
Lithium batteries don’t suffer from either high drain or low voltage issues. They hold charge for longer and operate in a wider range of temperatures than other battery chemistries. Lithium batteries are therefore ideal for devices that require a voltage higher than 1.2V or which operate at temperature extremes. They also come in higher capacities than other battery chemistries, which makes them an attractive option for travelers that have no access to electricity for a long period of time. For example, a backpacker who wants to take many pictures with his AA-battery-powered digital camera might find long-lasting lithium batteries very convenient. However, lithium batteries are the most expensive type of battery, costing more than LSD batteries and approximately 10x as much as Alkaline batteries and can only be used once. It therefore makes economic sense to use Lithium batteries sparingly.
Rechargeable batteries come in many different chemistries, but over the past decade NiMH (Nickel Metal Hydride) is by far the most efficient, cost-effective and popular chemistry for use in AA or AAA batteries. The first NiMH batteries to come out a couple decades ago were all of the high self-discharge variety. It wasn’t until 2005 that low self-discharge NiMH batteries became available.
High self-discharge NiMH AA or AAA batteries have low internal resistance and can be produced with high maximum capacities. Therefore, historically, they have been a popular alternative for use in high-drain devices, most especially digital cameras.
Unfortunately, two issues cause many people to be give up on high self-discharge NiMH batteries, in favor of Alkaline:
- They are often bundled with poor chargers. Low quality chargers typically undercharge or overcharge AA batteries. Undercharged batteries don’t last as long in the device, while overcharging harms batteries and can greatly decrease the number of potential recharges.
- The name “high self-discharge” refers to the fact that NiMH batteries discharge at a high rate when not being used. Such batteries have the temporary advantage of starting with a higher amount of charge, but most of this advantage is lost just 24 hours after being fully charged, and after 4 or 5 months they will have no charge left at all. Nobody wants to frequently change batteries for devices that are rarely used.
Such batteries can be useful in digital cameras or other high drain devices when paired with a high quality charger, especially if charged just before use. However, there’s no particular reason to use them anymore. This is because superior LSD NiMH battery options are now widely available, including high capacity options.
Low self-discharge NiMH (LSD) batteries are currently the best option for most applications requiring AA or AAA batteries. Unlike high self-discharge batteries, the rate of discharge is low, comparable to Alkaline batteries. Typically, 85% to 90% of charge is retained after a year of non-use, and 70% after 5 years. These NiMH batteries are approximately 70% charged at the factory so are typically labeled “pre-charged” or “ready-to-use.” This type of battery also typically lasts for over 1000 recharges, as compared with 100-500 for the high self-discharge variety. A rechargeable battery is considered at the end of its useful life when it can no longer charge to at least 80% of its original capacity.
The bottom line is that low self-discharge batteries are more expensive than high self-discharge, but they last decades, retain charge, and really have no drawbacks other than the initially higher price.
A low self-discharge battery paired with a poor charger can still lead to a poor user experience. But there are several great chargers on the market, which I discuss later in this post. Before doing that, here’s some more detail on the different generations of low self-discharge batteries.
History of LSD Batteries Since 2005
Rather than rehash Eneloop history and the different generations of batteries previously discussed on this site, this year I provide only a brief summary.
Sanyo invented the LSD (low self-discharge) battery and began selling Eneloop LSD batteries in 2005. A few years later, many other LSD brands came to market.
At first, all LSD batteries were produced in Sanyo’s factory in Takasaki, Japan. But within a few years, factories in China learned how to produce LSD batteries, though at a lower quality level. Sanyo was sold in 2009, resulting in the Eneloop brand going to Panasonic, while the Takasaki factory went to Fujitsu.
The Takasaki factory achieved numerous minor process and technology improvements from the original 2005 version over the years. These improvements resulted in higher capacity options, a longer life time for the battery (more recharges), and a lower discharge rate. The improvements over the first 5 years were rapid, but since 2010 the improvements have been very gradual. This is reflected in Eneloop marketing claims, which have changed by very small increments since 2010, by which time the so-called 2nd generation Eneloop batteries had completely replaced the first generation in the marketplace.
Given the very gradual improvement since 2010 and the high quality of batteries coming from the Takasaki factory, anyone who purchases two packs of Takasaki-sourced Eneloop batteries produced months apart from each other will find that they perform almost identically. On the other hand, a pack of Eneloops produced in 2017 will have better performance characteristics than Eneloops produced in 2011, particularly with regards to battery lifetime and charge retention.
A number of battery enthusiasts who have tested low cost Amazon Basics LSD batteries have claimed that they perform similarly to 2nd generation Eneloops from 2010 and lag behind batteries produced in the last few years on a number of performance characteristics. It’s also unclear which Amazon Basics LSD batteries are currently sourced from Japan, if any. I therefore no longer recommend purchasing Amazon Basics LSD batteries. Paying more up front for moderately better batteries makes sense, given that you’ll be using your LSD batteries for many years.
High capacity Eneloop batteries first came out in 2011. These batteries are more expensive and start with a higher capacity, but the trade-off is fewer recharges, approximately 1/4 as many. High capacity batteries produced in Japan rapidly improved over the following 2-3 years, so it’s a good idea to purchase high capacity LSD batteries that were produced after 2013.
Another style of LSD battery is the Lite version, which is slightly slimmer and will be more suitable for devices that have slightly narrower than usual battery compartments. They are also the LSD battery type most recommended for use DECT phones, because they can better handle a constant stream of trickle charge. The Lite style has been produced since 2010.
See the Eneloop101 site for a detailed compilation of LSD product releases over time, as reflected in the Eneloop product line.
The LSD capacity/longevity trade-off: Higher capacity means fewer recharges
Though Fujitsu’s Takasaki, Japan NiMH plant has produced high quality LSD batteries for Eneloop, Fujitsu, and many other brands, this does not mean that all LSD batteries produced there are identical. For starters, Eneloop, the original LSD battery brand, has produced several different capacities of both AA and AAA batteries since 2011.
Panasonic labeled the first high capacity AA batteries as having a capacity of at least 2400 mAh and more typically 2500 mAh, which was 500 mAh higher than the standard Eneloop batteries. They also labeled these batteries as being able to recharge 500 times, as opposed to the 1500 recharges claimed by standard Eneloops (the 1500 claim for standard Eneloops has since increased to 2100 with 4th generation batteries sold since 2013).
In addition to a higher capacity for the Eneloop brand, by 2011 many other brands were competing with Eneloop with a variety of mAh capacity claims. Some of these claims were accurate, and some were not. Some were coming from Japan, and some were coming from China.
Battery enthusiasts have put many of these competing batteries to the test over the years, and you can see results of such testing at forums such as the “batteries included” section of candlepowerforums or review sites such as wirecutter.
What I found from wading through all these reviews is consistent with what I learned from my contact at Fujitsu:
- The higher the specified maximum capacity of the battery (mAh), the lower the number of times that battery can be recharged. Each battery brand produced at the Takasaki plant will have a specified capacity, understanding that higher capacity necessarily means lower number of recharges.
- The higher the battery capacity, the more it costs, with the mAh/cost ratio between standard and high capacity staying about the same for a given brand.
- The number of recharges stated in marketing claims may be true in ideal use and storage conditions but actual number of recharges in everyday use tends to be less than what is stated on the package. Furthermore, batteries degrade gradually in terms of maximum storage capacity. The maximum storage capacity degrades more slowly for batteries that have smaller initial capacity. Higher initial capacity batteries typically have higher capacity for at least a year or two of typical use. However, after a few years, maximum capacity decreases, often falling below the maximum capacity of batteries that initially started with moderately lower capacity. Of course, all these calculations are complicated by the fact that the higher capacity batteries don’t need to be recharged as often, as they do have the higher capacity to last a bit longer between charges. It’s difficult to test real, everyday use to confirm how all the various different capacities of battery perform, because everyday use varies so much between households. However, many anecdotal reviews and individual tests on battery enthusiast sites seem to back up the idea that higher capacity batteries degrade more quickly than lower capacity batteries.
- The number of times an LSD battery can be recharged while still usefully holding charge is so high that many people don’t really care about that number, and focus on the maximum capacity at time of purchase. Such buyers may be disappointed 2-3 years later when the maximum capacity is significantly smaller.
- Japanese-made LSD batteries last for more recharging cycles than LSD batteries sourced from China, when comparing same-capacity batteries.
- Japanese-made LSDs self-discharge at a slower rate than LSD batteries from China, when comparing same-capacity batteries.
- LSD batteries from both Japan and China improve gradually every year. For example, a never-used 2017 LSD battery made in China may actually perform better than a never-used 2010 LSD battery made in Japan.
Personally, I prefer to buy standard Fujitsu or Eneloop batteries which are likely to last for decades, rather than higher capacity batteries with a shorter lifespan and faster self-discharge rate. Others may prefer the higher capacity/shorter lifetime trade-off. Just understand that it is, indeed, a trade-off.
Recommended LSD Battery Brands
Perhaps this section should be Factory Recommendation, because my main piece of advice is to buy LSD NiMH batteries from Japan, which means the factory in Takasaki, Japan. Many battery brands are produced at this factory. With the exception of the Amazon Basics brand (some of which may have been produced in Japan), the performance of various battery brands sourced from this factory are all good, though they vary in initial capacity and number of recharges (see prior section).
The tricky part for consumers is that not all brands consistently source all their batteries from Japan. Duracell is an example of a brand that at one point sourced some batteries from this factory in Japan, and others from a factory in a China. I don’t know if Duracell still does this, but the fact that they used to do it is enough for me to steer away from buying Duracell pre-charged batteries, because I don’t want to spend the time to figure out if they’re coming from Japan or China.
If you want to keep your life simple, buy brands that are always sourced from Japan. There are likely many LSD battery brands that are only sourced from Japan. Here are three that I’m aware of:
Another tip is to make sure you buy from a reputable retailer such as Costco, NewEgg, or Amazon. When buying online from NewEgg or Amazon, be sure to buy direct, not from a third party merchant whose reputation is unknown. There have been instances of third-party merchants repackaging and falsely relabeling inexpensive batteries.
I used to recommend Amazon Basics as a budget alternative. However, Amazon Basics batteries appear to be using LSD battery technology that is over 5 years old. Each year, other brands get slightly better as the batteries from Japan continue to improve, while Amazon Basics batteries stays the same. It’s also unclear which if any of these Amazon Basics batteries come from Japan.
You can save a few dollars buying Amazon Basics LSD batteries, but my opinion is that it’s worth spending a few extra dollars for better batteries that you’ll be likely be using for the rest of your life.
Rather than provide links to dozens of possible battery configurations, you can decide for yourself what number of batteries to get with these four general brand searches on Amazon:
You can often get a better deal buying batteries as part of a bundle that includes a charger, AA batteries, and AAA batteries such as this Eneloop bundle:
What to Look for in a Budget Charger
I’ve written about chargers several times before, so with this post I’ll just briefly summarize the “smart charger” features every quality charger must have in order to earn my recommendation:
- Must reliably cut off charging just when the battery is full. Not earlier. Not later. Negative Delta V is the most reliable method.
- Must have independent charging channels for each charging bay. Most low cost chargers have “paired bays”, which means 2 pairs of bays in a typical 4-bay charger. The pair of batteries stop charging, or charge at a much reduced rate, when the first battery of the pair is full. The inevitable result of paired bays is that at least one of the batteries will end up undercharged or overcharged. Undercharged will mean the batteries run out quicker in devices, overcharged is going to reduce the lifetime of the battery, and in some cases lead to a battery being destroyed from overheating.
- Chargers capable of charging rapidly must be able to detect excessively high temperatures and automatically stop charging.
Note that the term “smart charger” is a marketing phrase which can and has been abused to have many meanings. The more specific features to look for are proper circuitry to detect when a battery is full (negative Delta V) and independent charging channels.
Every model that I’ve come across with the first two features also tends to have two additional helpful features:
- an LED light or LCD display that is independent for each bay.
- The ability to mix and match different sizes and capacities of batteries.
That’s the essentials, but I go into more detail about what makes for a good charger here.
Extra Features to Look for in Premium Chargers
Budget chargers typically cost under $25, and can effectively cost a bit less when purchased in combination with batteries. Premium chargers typically cost between $35 to $100. Good places to buy premium AA/AAA battery chargers include Amazon, Newegg, and DC Workshop.
I will not consider recommending any charger, budget or premium, unless it has the features described in the prior section. The premium chargers recommended below all have these required features and many more.
Here’s a list of the most important other features to look for in premium chargers beyond the minimum already described:
- Higher charging rates (a feature one of this year’s budget chargers also offers)
- Safety feature(s) to cutoff charging if batteries get too hot when charging at a high rate
- Automatically switching to a “trickle charge” when batteries are full
- The option to control each bay independently for rate of charge and discharge
- An LCD display (independent, for each bay) providing additional information beyond charging/done
- The ability to “refresh” a battery by discharging all the way and recharging to full, which is particularly helpful with brand new batteries
- Testing functions
All the premium chargers I recommend offer these features. They differ in the degree to which they offer these features, how difficult they are to use, and whether there is something awkward about using the charger.
In addition to the required features listed above, there are a few optional features that some users may find helpful:
- Handle more battery chemistries beyond NiMH. Rechargeable Li-Ion batteries in particular have been growing in popularity.
- A fan which turns on at higher temperatures, to allow charging to continue at safe temperatures.
- Make it very easy to pick out which batteries should be discarded. All premium battery chargers test capacity, which can be useful for this purpose. However, even more useful is measuring internal resistance.
Recommended Budget AA/AAA Chargers
Most inexpensive AA/AAA battery chargers are terrible. But at any given time, there are typically 1-3 models available in the U.S. for under $25 that fit all the criteria for a good budget charger. This year, I recommend 2 models. If you want to read about these two chargers in great detail, read Best of the Budget Chargers: BQ-CC55 vs FCT344 vs BQ-CC17. Here’s the very brief summary:
The Panasonic BQ-CC17SBA has been this site’s top pick since I first wrote about it three years ago. In addition to having all of the required features listed in the What to Look for in a Budget Charger section, it is compact, and it is included with several different economical Eneloop bundles. It is simple to use and difficult to abuse. It has a slow charging rate but this enables it to work with a wider variety of NiMH batteries than other budget chargers that attempt to charge at a faster rate. It even works well with older, lower quality high self-discharge NiMH batteries that some budget chargers struggle with.
You can buy it alone for about $20 but that makes no sense as you can also get it with 4 AA Eneloops for a couple dollars less:
Or as part of a bigger bundle:
If you want your budget charger to charge at a faster rate than 300 mA, the Fujitsu FCT344 and Panasonic BQ-CC55 chargers are the two obvious options to consider. These two were discussed alongside the BQ-CC17SBA elsewhere on this site. We do not recommend the BQ-CC55 because we were not impressed with its thermal management.
We tested all three models under many different scenarios with a variety of old and new batteries of both high and low self-discharge batteries. The BQ-CC55 had the highest charging rate of the three, which under some scenarios caused batteries to get too hot to touch. In one instance, batteries in the BQ-CC55 reached 53° C (127° F), at which point the test was halted for fear of causing the battery to melt.
The FCT344 also got pretty warm to the touch, especially with older, high self-discharge batteries. However, battery temperatures in the FCT344 were much lower than the BQ-CC55 during testing of all LSD batteries. When using older, low quality, high self-discharge batteries with the FCT344, the temperatures did begin to rapidly rise, but then the thermal protection circuitry triggered, shutting down the charger. The FCT344 is therefore unsuitable for use with older, high self-discharge batteries.
We do recommend the FCT344 as a good charger for use with LSD batteries. In the U.S., it can only be purchased as part of a bundle with Fujitsu batteries:
Recommended Premium AA/AAA Chargers
In the past, this site recommended a number of different charger brands from La Crosse, Maha, and Opus. In 2017, FilterJoe researcher Jim Hyman extensively tested several models from these different brands. Detailed write-ups for Jim’s testing results are forthcoming. Jim’s testing has caused some changes in this site’s premium charger recommendations.
The most important change is that we now believe that one charger brand beats out the others as the best combination of features, cost, and ease of use. That brand is the Powerfocus Opus.
I have been recommending user friendly La Crosse models for years and I continue to use a La Crosse model for my everyday charging needs. But if I were to buy my first premium charger today, it wouldn’t be La Crosse. It would be Opus.
The La Crosse charger’s biggest selling point compared with other premium chargers is ease of use. Jim found the Opus just as easy to use, and in some ways easier. While Opus and La Crosse are roughly tied in terms of ease of use, the Opus costs less, has greater flexibility, and packs more features, including a feature useful for weeding out worn-out batteries (internal resistance testing). Top-of-the-line Opus models also have a fan that starts up whenever battery temperature exceeds 40° (C). There are only 2 downsides to the Opus Charger that I can think of:
- Opus firmware in models produced prior to 2014 had issues which led to overheating. It is still possible to buy older models, and these should be avoided. The issue was solved with a firmware upgrade to 2.1, which you can see briefly displayed on the leftmost column when turning on any Opus charger. When using a new Opus, be sure it flashes a number that is at least 2.1 when first turning it on.
- The manufacturer of the Opus brand has no web site or technical support. Note that DC Workshop does provide technical support and a one year warranty on Opus charger models they sell, and is the only vendor that sells the BT-C3400 with 3.1 firmware.
Many Opus models have a maximum charging rate of 1400 mA with 2 batteries inserted, or 1000 mA with 4 batteries, which is lower than the top models from La Crosse and Maha. However, the two most expensive Opus models do charge at a maximum rate of 2000 mA with 2 batteries inserted: BT-C3100 and BT-C3400.
There are many Opus models, most of which differ by which accessories are included (C and D adaptors, auto adapters, etc.). The basic model is this one:
You can see the different Opus models on Amazon with this link, each of which comes with different combinations of car adapters and C and D battery adapters as well as options for additional battery chemistries:
The top of the line Opus model has a fan, has higher charging rates, and is able to charge Lithium Ion and NiCd batteries in addition to NiMH. It is typically $10-$20 higher than the base model:
Note that the BT-C3100 is physically identical to the BT-C3400 model, so purchase whichever is available at the best price. An advantage of buying the BT-C3400 over the BT-C3100 is that you are guaranteed to be getting firmware version 3.1 with the BT-C3400, which so far as we know is equivalent to version 2.2 on the BT-C3100. Also, it comes from DC-Workshop, which offers technical support. Both versions 2.2 in the BT-C3100 and 3.1 in the BT-C3400 have improved fan support for these identical models, as well as other minor improvements.
To reiterate about firmware version numbers: be careful buying a bargain-priced Opus charger from a third-party merchant on Amazon, as it may be a several-year old model with firmware 2.0 or lower. When using an Opus charger for the first time, be sure it flashes a number that is 2.1 or higher when turning it on.
Lithium Ion batteries, by the way, are not AA batteries operating at the usual 1.2 Volts or so, even though they have a similar shape. They operate at 3.7 Volts, and they are not compatible in most equipment that uses AA or AAA batteries. This being a guide about AA and AAA batteries, there’s no reason to discuss here Lithium Ion batteries and their primary use case (tactical flashlights). For more information, you can read a guide to tactical flashlight battery options here or here. You can read about Lithium Ion battery safety here.
While the Opus has quite a few features related to testing, a more popular model for those who desire a greater degree of flexibility and testing possibilities is the venerable Maha MH-C9000. This model has a higher learning curve and requires many more button presses for simple operations such as charging 4 batteries at 500 mA instead of the 1000 mA default rate.
The most popular of the Maha models is:
But they offer several other models as well:
I’ve recommended two La Crosse models many times in the past, the BC-700 and the BC1000. If you own either of these two models, there’s no reason to stop using them. They’re fine chargers. But if you’re shopping for a new charger, here are a few reasons I think you’re better off buying an Opus model:
- La Crosse models do not charge heavily discharged batteries with very low voltage. In fact, these models identify such batteries with a cryptic “null” message which the manual claims means that the battery is no longer usable. Most “null” batteries are simply low in voltage and need to have their voltage raised before a La Crosse charger will charge them normally. All prior La Crosse discussions on this site have explained workarounds for this issue.
- Comparable La Crosse chargers cost a bit more than Opus chargers. The BC-700 model is not very expensive but costs more than the comparable Opus model, the BT-C700 (both of these models have a 700 mA maximum charge rate). The high end La Crosse BC-1000 model costs more than any Opus model, including the much more capable Opus BT-C3400 (and the identical BT-C3100).
- La Crosse does provide customer support, but there are many reports of customers not so happy with their support.
- According to our tests, La Crosse discharge and testing functions consistently over-reports battery capacity by 6% to 8%, as compared with other charger brands that have testing functionality built in to their chargers.
- La Crosse is one of many brands that license this China-sourced product. Other brands representing the exact same product include Technoline (Germany) and Voltcraft. There may be more. While this is not in and of itself a bad thing, understand that the engineers who designed and truly understand the technology behind this product do not work for La Crosse. La Crosse is a marketing company that purchases their chargers from China, along with Technoline and Voltcraft. Though I’ve been unable to confirm it, it’s also possible that Youshiko and Dayshop are two other brands for this product.
Given all these points, and Jim’s extensive testing of the Opus, we no longer see compelling reasons to purchase a La Crosse charger (or any of its other names) over an Opus charger at this time.
Storing AA and AAA batteries
Using or storing batteries in a hot environment is bad for battery performance, both short and long term. The best way to store batteries is in a cool, dry place. Avoiding hot places like an enclosed car in the summer or the hottest part of your house will go a long way. Some people seem to believe that storing batteries in a refrigerator is helpful, but I haven’t tested this. Also note that Panasonic recommends against storing Eneloops in a refrigerator.
If you have many devices using AA and AAA batteries, you’ll likely want to always have a few spare AA and AAA batteries charged and ready to go. That way, you can swap the batteries and keep using the device, while the depleted batteries go into the charger.
How to store and organize all the extra batteries? Personally, I’ve been using the following for the last 5 years:
If you need cases to carry sets of 4 AA batteries for your camera or other portable equipment:
Some people store batteries in their charger. That’s fine for a few days if it’s one of the smart chargers recommended here. But do understand that in most models, there will be a trickle charge going into the batteries, which is not good for battery longevity if you leave batteries in the charger for months.
Under no circumstances do you want to store your batteries in a dumb charger or low quality charger. You will gradually ruin your batteries.
When to Use Alkaline or Lithium Batteries (hint: rarely)
Some devices require more than 1.2V to operate correctly (or in some cases, at all). NiMH batteries can in many cases briefly provide higher than 1.2 Voltage, but only for a minuscule fraction of their stored capacity (In other words, they might work for a few minutes and then quit when the voltage drops to the usual 1.2V).
Alkaline batteries can operate at 1.5V for at most 1/3 of their stored capacity, while lithium batteries last much longer at the 1.5V level.
Note that a device that requires 1.5V batteries means that your Alkaline batteries will quit working with 2/3 of the stored energy still remaining. This has always struck me as a big waste, which is why I try to avoid devices that require 1.5V, whenever possible. But if you do have such devices, you’ll need to use either Alkaline or Lithium AA/AAA batteries. Lithium will last longer, both because there is more stored energy, and because most of this storage energy can be used while still operating at close to 1.5V.
Another rare use case for Alkaline batteries is in devices that have slightly smaller than standard-sized AA battery compartments. The LSD batteries are very slightly thicker than Alkaline batteries and therefore won’t fit in such compartments, while Alkaline batteries can (barely) fit.
With the vast majority of devices that require 1.2V batteries and have standard sized battery compartments, the only advantages to using Alkaline batteries are low initial cost and that you don’t have to recharge them when done. As previously discussed, disadvantages include higher cost in the long term, adding to the landfill, and not functioning well in high drain devices.
FilterJoe’s first version of this AA/AAA battery guide from 6 years ago isn’t dramatically different from this latest version. That’s because the rate of change is slow in the relatively mature industry of AA/AAA batteries.
While the technology is the same, there have been some improvements in battery chargers in both the budget and premium categories, which caused specific recommended models to change. While low self-discharge (LSD) batteries are still the most economical purchase, Eneloop is now just one among many brands. LSD batteries manufactured in Japan are all reliable and trustworthy, because they all come from the same factory in Takasaki, Japan.
Despite being available for over a decade, most consumers are still not aware of how much better LSD AA and AAA batteries are compared with the alternatives. It’s somewhat puzzling to me how long it is taking for this type of battery to dominate the market. This site will continue to write about LSD batteries for many years to come, until such time as it gets replaced with better technology, or becomes so common that HSD NiMH and Alkaline batteries are being phased out. I don’t expect that to happen any time soon, despite the overwhelming benefits of LSD batteries with regards to cost, performance and environmental impact.