Customer Reviews: Panasonic BK-4MCCA8BA Eneloop AAA 2100 Cycle Ni-MH Pre-Charged Rechargeable Batteries (Pack of 8)
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on September 12, 2014
Lot's of confusion about "codes" so I put a chart up explaining the difference.

Standard Eneloop models:
1st Generation Eneloop model numbers and specs
AAA: HR-4UTG 1000cycles Rated 800mAh. Min. 750mAh
....AA: HR-3UTG 1000cycles Rated 2,000mAh. Min. 1,900mAh
.......C: HR-2UTG 1000cycles Rated 3,200mAh. Min. 3,000mAh
.......D: HR-1UTG 1000cycles Rated 6,000mAh. Min. 5,700mAh

2nd Generation Eneloop model numbers and specs
AAA: HR-4UTGA 1500cycles Rated 800mAh. Min. 750mAh
...AA: HR-3UTGA 1500cycles Rated 2,000mAh. Min. 1,900mAh

3rd Generation Eneloop model numbers and specs
AAA: HR-4UTGB 1800cycles Rated 800mAh. Min 750mAh
...AA: HR-3UTGB 1800cycles Rated 2,000mAh. Min 1,900mAh

4th Generation Eneloop model numbers and specs
AAA: BK-4MCC 2100cycels Min. 750mAh
...AA: BK-3MCC 2100cycels Min.1900mAh
......C: BK-2MGC 1000cycles Min.3000mAh
......D: BK-1MGC 1000cycles Min.5700mAh

1=D 2=C 3=AA 4=AAA

I just ordered these and got the 4th gen!!!!
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Style: AA|Size: 4-Pack|Vine Customer Review of Free Product( What's this? )
Summary: Eneloop are the gold standard in LSD Batteries, and they are now that much better...If you don't know what an LSD battery is, you should find out.

LSD= Low Self Discharge. Some companies call them "Pre-charged," but it's the same thing.

I've been a fan of rechargables since the 70's when my father had a bunch of GE Nicad cells which had capacity of perhaps 400 mAH. Nicads had so much more punch than alkaline batteries. For years and years I kept chasing the performance promise of higher capacity, 1200 mAH, 1400mAH, 1800mAH, 2100 mAH, 2300 mAH, 2500 mAH!!! 2650mAH!!!!!

Well, I ended up having all sorts of problems with the 2500 and 2650. It turns out that, besides a slightly larger diameter case which caused fit problems in some devices, they also had horrendous self- discharge. Easily half the charge was gone in a month, and in 2-3 months they were often dead.

After finding out about Eneloops (Sanyo Eneloop was the original LSD battery chemistry: Panasonic = Sanyo = Eneloop after Sanyo was bought out by Panasonic), I've phased over - perhaps 80% of my rechargeables are now LSD. The earlier LSD were 2000 mAH, as are these. These newer ones are good for 2100 cycles. Note that there is an alternate type of eneloop "XX" that give you 2500 mAH, but they are supposedly only good for 500 cycles. 500 cycles isn't bad though - even if you were to recharge them once a week you would still get 10 years... I've had good luck with other brands of LSD - Duracell Precharged and Amazonbasics White (The Amazonbasics black are made in China, the white ones are made in Japan and believed to be made by Panasonic)

Brief history of rechargeable batteries: In the beginning there was NiCad and all was good, but people found that the cells of Nicad had memory and that was bad. So then there were the cells of NiMH which could store more power than Nicad and had no memory, and that was good.

But these cells of NiMH also lost charge (self-discharge) fairly quickly, so that in a few months they were dead, and this was almost worse than memory. Alas, the men were angry and the women lamenting "Why have the electrons of NiMH abandoned us?

Then the prophet Sanyo came and said "I have made a NiMH cell that has a very low self discharge and I will give it a name like no other. I will call it ENELOOP"

And all the people said "Huh?" for the name was goofy in addition to being like no other. But soon the land was filled with celebration as they found that these batteries would hold their charge for months, even as long as a year!

The latest Eneloops recharge 1500 times, the earlier, 1000. Assuming you charge them every other day, that's 5-1/2 years for the older ones, over 8 years for the "Eneloop 1500" Other people rebrand Eneloop as their own (Most of the Duracell "pre-charged" appear to be Eneloop) but I still prefer the original - especially as the price isn't that much less for the other brands.

If you have questions or comments, or if you found this review helpful, please let me know!
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on January 30, 2015
I've been using a variety of Ni–MH batteries for a while now but for sheer reliability and longevity the Eneloop ones are hard to fault. This is the 4th generation of the Eneloop range the first coming to the market in around 2005, over time the number of charges has increased from the original 1000 cycles up to a claimed 2100 as well as extending the charge they retain in storage for longer. Since Panasonic took over Sanyo in 2013 the they retain the Eneloop branding, this model is BK-3MCCE the prior generation is HR-3UTGB the cycles up from 1800 on that model.

It's easy to spot the newest model purely because they are Panasonic branded
The cells are quoted as retaining up to 70% of their capacity for 5 years and are ready to use out of the box

I tested the pack I got and the capacities ranged from 2020-2078 mAh this can vary a bit but you're guaranteed a minimum of 1900 mAh. Unlike some other makers you can be sure you'll get the quoted capacity Despite the higher cost per battery the longevity of the Eneloop batteries has been very good I've had sets for a good while now (over 5 years) and they're still going strong where as some budget offerings have lost their capacity or worn out after a few years. I've also never had a problem with the Eneloop cells fitting, in the past a few makers have played around the standard AA size and some are a bit longer or larger in diameter this can cause problems on some devices fitting wise.

On the packaging Panasonic recommend using their own chargers, but I've never had a problem with a good quality third party smart/intelligent charger with any make of battery it's well worth investing in one of these as it can extend the life of cells and avoid overcharging problems that some timer/manual chargers have.

**A few chargers worth looking at**

Maha MH-C9000 (very advanced high end charger)
Powerex MH-C9000
Technoline BL-700 or BC1000
Foxnovo F-4S
The official Panasonic charger is: BQ CC16 this is an intelligent charger with individual monitoring and charging of cells, I don't recommend the basic BQ CC18 it works fine but it is timer control only.
A decent budget 8 cell intelligent charger is the KooPower 8 Bay smart charger (this seems to be available in a few brand names same design though)

Some of the top end chargers have multiple charging speeds and testing capabilities as well as discharge/re-fresh cycles. If you don't need these features then just go for a normal smart charger it's worth the small additional cost.

There are some cheaper batteries out there, and some decent budget offerings too. But despite the higher cost this seems to be levelled out with the lifespan of the batteries. Hard to fault really a very reliable and solid offering and suitable for use in a wide variety of appliances even heavy drain items like flashes and digital cameras. For super high capacity users take a look at the Eneloop Pro range
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Scroll down to the end if you would like to see the detailed info for the codes.

I have been using Eneloops (along with Powerex, Imedion and Energizers) for about 5 years now and I have good things to say about Eneloops for the most part. I use them mainly for my speedlites (Canon 600RT, Canon EX580ii, YN600RT, YNE3RT and so on) but you can use them for anything that uses an AA battery. These are NiMH which means they do have a discharge over time so my advice is to use these in places where there is a larger power consumption and needs recharge more frequently like in my case an external flash. You would probably not want to use it at places like a regular wall clock.

They have always performed quite well over the years although they do tend to develop "memory" in which you would need to fully discharge them once in a while and then have them fully charge.

Over the years, I have gathered around 7 sets (each set = 4 batteries) of Eneloops. I usually use my Maha chargers to discharge and charge them. I recently got a EBL charger that I will be testing out to see how well it works.

The name in this Amazon listing claims "2100mAh" but yet the actual packaging states "2000mAh" and the battery itself claims "1900mAh." So quite honestly, I do not know which is the most accurate of the three. It could very well be a marketing move to lured potential buyers.
They seem to hold their charge very well but when you do notice that the batteries are not doing so, that would usually mean you would need to discharge them first.

My tips for managing these sets of batteries is to label each set accordingly so when I charge them, I usually keep them charging in the same charger. This is similar to the idea of rotating your tires on your car in which you wear them out equally rather than overworking any one specifically more than the others. When I put these in my flash, I know exactly which set to put in without mixing in a dead battery by mistake.

1st generation:
HR-4UTG: AAA(85% Claimed capacity after *31 year, *2date: November 2005) *9
HR-3UTG ...AA (85% Claimed capacity after *31 year, *2date: November 2005)
HR-2UTG C (*1 date: 2007)
HR-1UTG D (*1 date: 2007)
Can be used in weather as low as -10degrees

2nd generation:
HR-4UTGA: AAA (75% Claimed capacity after *33 years, *2date: November 2009)
HR-3UTGA: ...AA (75% Claimed capacity after *33 years, *2date: November 2009)
Can be used in weather as low as -20degrees

3rd generation:
HR-4UTGB: AAA (70% Claimed capacity after *35 years, *2date: November 2011)
HR-3UTGB: ...AA (70% Claimed capacity after *35 years, *2date: November 2011)
4th generation:
BK-4MCC: AAA (70% Claimed capacity after *35 years, *2date: April 2013)
BK-3MCC: ...AA (70% Claimed capacity after *35 years, *2date: April 2013)
BK-2MGC:.......C (70% Claimed capacity after *35 years, *2date: April 2013)
BK-1MGC:.......D (70% Claimed capacity after *35 years, *2date: April 2013)
5th generation: Export
BK-4MCC: AAA (70% Claimed capacity after *310 years, *2date: August 2015*13)
BK-3MCC: ...AA (70% Claimed capacity after *310 years, *2date: August 2015*13)
5th generation: Japan
BK-4MCC: AAA (90% Claimed capacity after *31 year, *2date: August 2015*13)
BK-3MCC: ...AA (90% Claimed capacity after *31 year, *2date: August 2015*13)

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on April 12, 2015
Out of the box, an initial discharge and refresh using an Opus BT-C2400 charger (3 discharge + 3 charge cycles @ 200mAh) yielded 91% of the 800mAh capacity and also less than the stated 750mAh minimum.
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on October 27, 2014
These are the best rechargeable AA batteries money can buy. If you want to always have the ability to power your electronics powered by AAA, AA, C, and D-sized batteries, then it's time for you to invest in an Eneloop infrastructure. These batteries pack some mAh into familiar form factors, and retain that charge for a long, looooooong time. They don't take long to charge, and they'll outperform your standard Duracell or Energizer alkaline batteries -- they also provide a more stable voltage for a longer period. Of the rechargeable batteries out there, Eneloops are the best according to numerous reviews over the internet.
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I have done extensive study on low-self-discharge (or 'pre-charged') rechargeable batteries, starting from early 2007 when the original Sanyo eneloop cells were introduced to the US market. Subsequently I have tested Sanyo 2nd-gen eneloop, followed by Sanyo 3rd-gen eneloop and finally these Panasonic 4th-gen eneloop.

Every single eneloop cell I have purchased in the past 8 years, including the original ones, are still in good working conditions. That says a lot about the quality of eneloop batteries. But the question is: are there any REAL improvements in later generations of eneloop batteries?

The advertised capacity ratings for all eneloop (1st to 4th-gen) batteries are identical:
- AA cells are rated "Typ. 2,000mAh, Min. 1,900mAh"
- AAA cells are rated "Typ. 800mAh, Min. 750mAh"

Actual capacity measurement, using my old La Crosse BC-900 Battery Charger, also showed that capacity numbers are consistent from 1st to 4th-gen. In fact, my measured results are consistently about 4-5% higher than the advertised values.

[Charge Retention Rate]
With each new generation, eneloop's long-term charge retention rate gets a little more ambitious:
- 1st-gen claims "85% after 1 year"
- 2nd-gen claims "85% after 1 year; 75% after 3 years"
- 3rd-gen claims "90% after 1 year; 80% after 3 years; 70% after 5 years"
- 4th-gen claims "90% after 1 year; 70% after 5 years"

Notice that those numbers are essential the same, just extending over longer period of time. In fact, I have tested a set of first-gen eneloop cells after 3.5 years in storage, and they still contain around 75% of rated capacity. To me, this shows that there are no real changes in the charge retention rate among different generations.

[Cycle Life]
The main difference between different generations is in the advertised lifespan:
- 1st-gen: '1000 cyles'
- 2nd-gen: '1500 cycles'
- 3rd-gen: '1800 cycles'
- 4th-gen: '2100 cycles'

Let's consider how long it takes to actually test a rechargeable battery through 2100 deep discharge/recharge cycles:

The standard test procedure calls for charging at 0.2C (~5 hours) and discharging at 0.2C (~5 hours), plus cooling period of one hour each between charge and discharge phases. So a complete cycle takes about 12 hours. To exercise a battery through 2100 cycles would therefore take nearly three years!

However, 3rd and 4th-gen eneloop cells are both released less than 2 years from their previous generations.

[Bottom Line]
My theory is that all eneloop 2nd/3rd/4th gen batteries are in fact made with the same battery technology. It takes many years to collect the actual cycle life and charge-retention rate data. Therefore only later generations are able to advertise higher number of cycles and longer storage life.

If my theory is true, then it follows that there's no reason to pay higher price to get the latest 4th-gen eneloop. Any earlier generation of eneloop would perform just as well.

Finally, if you are extremely 'value conscious' like me, consider the following rebranded eneloop batteries and get the same quality for even less:
AmazonBasics Pre-Charged Rechargeable Batteries (in white wrappers) are rebranded Sanyo eneloop.
AmazonBasics High-Capacity Pre-Charged Rechargeable Batteries (in black wrappers) are rebranded SANYO eneloop XX batteries
Duracell Ion Core AA Rechargeable Batteries are rebranded Sanyo XX, while Duracell Ion Core AAA cells are rebranded eneloop AAA batteries

[Update on Dec 22, 2015]
For additional information on eneloop batteries in general, please refer to my newly updated "Panasonic/Sanyo eneloop FAQ":
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TOP 100 REVIEWERon January 14, 2015
This is the pinnacle of rechargeable AA and AAA batteries. These fourth generation eneloop 2100 batteries give performance that not only exceeds all other NiMH cells, but exceeds disposable alkaline cells as well. With a high capacity and extremely long service life, the eneloop 2100 can save you a ton of money, while also saving the environment from a ton of waste. We all need batteries, but if you want THE battery that will give you the best performance and long-term cost effectiveness, then this eneloop 4th generation 2100 is THE battery you want. It is THE battery that will perform. It is THE battery that will last.

These are NOT the rechargeable batteries you may remember from years past. Historically, rechargeable AA, AAA, C, D, etc. batteries have not been super practical. They did not last nearly as long as disposable alkaline, had a short service life, had terrible issues with memory, took 15+ hours to charge, quickly shrank in capacity, quickly self-discharged and were very expensive. They also did not work well in high-drain devices, and worked even worse with low-drain devices due to rapid self-discharge. In other terms, the practicality was limited and rechargeable batteries did not work well in many of our most common devices. And they got kind of a negative reputation due to this.

But oh how things have changed! Second, third, and now fourth generation NiMH technology has changed everything. Energy density is much greater. Memory is gone. Charging is rapid. Service life has gone from the low hundreds to the thousands of cycles. Self-discharge has all but been eliminated. And now NiMH works especially well in high-drain devices, in many cases lasting LONGER than premium alkaline batteries. In other terms, today's rechargeable NiMH batteries are more practical than alkaline batteries, and far more economical. At the forefront of NiMH technology is Sanyo, with their eneloop brand.

Eneloop (Sanyo, so technically Panasonic) is generally agreed upon to be the golden standard of NiMH technology. Their third generation NiMH batteries (often called the "eneloop 1800") were hands-down the best rechargeable cells on the market. Then they had to go improve it even more. These fourth generation cells (often called the "eneloop 2100") are amazing. Over the past 5 years of reviews, I've noted that most people benefit from rechargeable batteries, but not everyone. These fourth generation eneloop 2100's change that: everyone will benefit from these batteries. They are robust, have excellent capacity, and perform well in high-drain devices. Where these new batteries improve the most is with low-drain devices because self-discharge is so low that these give just as much run time as alkaline on even super low-drain apps (ex: clocks.) While these are among the more expensive of NiMH offerings, the higher capacity and longer service life of the fourth generation eneloop 2100 will save you significant money over cheaper NiMH cells in the long run.

These batteries are 2,000 mAh fourth generation rechargeable NiMH AAs, with an advertised service life of up to 2,100 cycles. Unlike many other brands I have used, Sanyo does not overrate their batteries. They guarantee the minimum capacity to be 1,900 mAh, and their batteries are consistently close to 2,000 mAh (by comparison, I have Tenergy and Duracell NiMH cells advertised to be 2,500 mAh but with an actual capacity of under 1,750 mAh.) This consistency in capacity translates to consistency in performance, as User Reviews of eneloop products clearly reflect.

Eneloops are praised not only for having a long service life, but also for holding a high capacity throughout this service life. Eneloop states the service life of these to be up to 2,100 cycles and I believe it. My second generation eneloops have at least 600 cycles on them and still push 85%+ original capacity. My third generation eneloops have a few hundred cycles on them and still push almost 100% original capacity. Most NiMH batteries can't do this.

These batteries improve from ultra-low self-discharge to ULTRA-ULTRA-low self-discharge. That is, you can charge these up and they can sit in storage for years and still keep a usable charge. Advertised as maintaining at least 70% of their charge at the 5 year mark, these practically hold their charge as well as disposable batteries. This makes the eneloop 2100 extremely practical for ultra low-drain applications that NiMH cells have historically not worked well with. Despite being suitable for these very low drain applications, these deliver equally impressive performance with high-drain applications, such as usage in a high-output flashlight. This ability to excel in both low- and high-drain applications makes the eneloop 2100 the most versatile NiMH battery ever made.

Unlike older NiMH cells, these eneloops are not picky when it comes to temperature. Capable of operating in lower and higher temps, these fourth generation cells can operate down to -4 degrees. So unlike older NiMH cells, you can put these in a flashlight you leave in the car and the battery will still perform even if exposed to temperature extremes.

Like other NiMH cells, these have a native voltage of 1.2v (which is lower than their top-off charge voltage.) With almost all modern devices, this does not cause any functional issues.

THE ENELOOP 2100 (for all applications) VERSUS THE ENELOOP PRO (for high-drain applications, formally called the XX)
Eneloop has historically had two different lines: a standard/general-use NiMH battery and a high-performance NiMH battery for high-drain applications. The current fourth generation offering is the eneloop 2100 (this battery, for general-use) and the eneloop Pro (for high-performance, high-drain.) With the previous third generation, this was the eneloop 1800 (general-use) and the eneloop XX (high-performance.)

The eneloop Pro is a very different type of battery than the 2100. The 2100 is a general-purpose battery that will work in almost all situations. The eneloop Pro is designed only for usage with extremely high-drain devices, and with normal and low-drain devices, it will not perform nearly as well as the eneloop 2100. The Pro has a higher 2550 mAh capacity, but only a 500 cycle lifespan. It also self-discharges more rapidly than the 2100: the eneloop Pro will discharge more in one year than the eneloop 2100 will in four years.

This new eneloop 2100 is a VERY capable battery and it performs well in most high-drain applications as it is. It does considerably better with high-drain applications than the previous third generation eneloop 1800, which means these fourth generation eneloop 2100's may work well in your higher-drain device even if the eneloop 1800 did not. With a lower price, a longer service life, and lower self-discharge rate, this 2100 is more suitable for the large majority of applications, and the eneloop Pro is best used only in limited applications with devices that are unusually hard on batteries.

These batteries require a charger that is capable of charging NiMH batteries. NiMH chargers are not generational specific (that is, the Sanyo charger you may have purchased with the third generation eneloop 1800's will charge these new fourth generation eneloop 2100's, and a charger sold with these new generation eneloop 2100's will charge eneloops of older generations.) Unless otherwise noted as being capable of charging different chemistries and/or different voltages, NiMH chargers should not be used to charge batteries of other chemistries (such as NiCad, LiFePO4, or LiMn, for example.)

I have found that a good-quality charger plays a big role in getting the best performance and your money's worth with rechargeable batteries, plus it gives an added safety factor. A quality charger can inform you about battery health, capacity, and charge in a fashion that attempts to maximize service life. I also have found that the very cheap super-rapid-chargers tend to decrease battery capacity and service life, and so I would advise against them. In fact, a poor-quality super-rapid charger is probably the only thing that would harm these robust eneloops. As eneloops are not the cheapest NiMH batteries, a good charger will ensure you get the best performance and maximum useful service life from your investment.

The Sanyo-branded chargers that come with some of these lots are great products. However, if you are purchasing a charger separately, I recommend considering one of the intelligent chargers that can charge batteries of different chemistries/voltages. Lithium cells have incredible energy density & are lightweight...the same lithium cell I use in my eCigerette is used to power Tesla vehicles! In the future I think we are going to see more consumer devices that use lithium cells, and so having a good quality charger that can charge both lithium and NiMH is a plus. I own a NiteCore IntelliCharger D4 that does NiCad, NiMH, LiFePO4, and LiMn/LiCo; it is one of numerous chargers praised for its performance and safety record. This has me covered for these eneloops, plus my IMR and ICR lithium cells for my eCig, plus my LiFePO4 cells for a flashlight. So this type of charger may be worth consideration.

Eneloop's 4th generation NiMH rechargeable batteries will save you money & resources over disposable batteries, while increasing practicality & performance. These new fourth generation eneloop 2100's are the most versatile NiMH batteries made, and given they excel in both low and high drain applications, this means you can use these for virtually any need you may have. With that kind of flexibility, they run circles around other NiMH cells, and are by far the best pick for ultra low-drain applications due to an incredibly low self-discharge rate. While the initial purchase price of these are higher than other NiMH cells, the high capacity and long service life will make these less expensive to own in the long run. These batteries are fantastic and worth every penny. They will serve you well for many years and save you quite a lot of money. I highly recommend them.
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TOP 1000 REVIEWERon May 30, 2014
I originally purchased a combination set of these eneloops that included the charger a few months back as I needed some decent rechargeable batteries for a variety of tasks including some solar lights. I actually didn't know much about these at the time but the price was right and I decided to give them a shot. And after using several of them for different things, I have been nothing but impressed, they are reliable and charge without memory and I liked them so much and have used most of the original set in the different things I needed AA batteries, I decided to purchase an additional 16 pack of them (direct from Amazon) (no charger).

Good batteries, maintain a good charge, rechargeable a lot without gaining a memory, what else can I ask for in a battery.
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VINE VOICEon August 1, 2014
For years I stayed away from rechargeable batteries because they always seemed to drain so quickly and had the "memory" problem. About two years ago I started buying the Envelops and I couldn't be more pleased. I've been using them in literally everything in our household that requires batteries and not only have a saved a ton of money on the regular non rechargeables but I feel like I'm helping the environment by reducing potentially harmful waste. I may be imagining it, and I haven't "tested" it but these seem to last every bit as long as regular batteries. If they don't, they're awfully close and when they do run out, the spares hold a charge so I've always got fresh ones and overnight the used ones are as good as new. I cannot imagine going back to buying those huge packs of batteries at Costco!
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