Customer Reviews: Panasonic BK-4HCCA8BA Eneloop Pro AAA New High Capacity 950mAh Typical Ni-MH Pre-Charged Rechargeable Batteries, Pack of 8
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[Note: The following is an updated version for my original “Sanyo eneloop FAQ”, first published in May 2012]

I have been using eneloop low-self-discharge NiMH batteries since beginning of 2007, and I'm completely satisfied with them. One thing I noticed is that newcomers to the rechargeable battery arena often have similar questions/confusions about eneloop. So here is my list of eneloop Frequently Asked Questions. This list is work in progress.

[Q1] Why are there so many eneloop batteries with different capacity ratings and cycle-life numbers?
[A] There are actually three families of eneloop batteries:
- Standard version: The original Sanyo eneloop (circa 2006) was rated for capacity of 2000mAh typical for AA (800mAh for AAA) and 1000-cycle lifespan. Subsequent generations advertise longer lifespan (1500/1800/2100-cycles) at the same capacity. The charge retention rates have steadily extended from "85% after 1 year" to "90% after 1 year; 70% after 5 years"
(Refer to my uploaded photo on how to identify different generations of eneloop cells)
- High-Capacity version: The original Sanyo XX (circa 2010) was rated for 2500mAh but only 500 cycles. The charge-retention rate is slightly poorer at "75% after 1 year". Newer Panasonic eneloop PRO bumped the capacity to 2550mAh and charge-retention rate to "85% after 1 year".
- LITE version: Those have half the capacity of standard eneloop but twice the cycle life. They are not marketed in the US.

[Q2] Do I get better performance from the latest generation Panasonic eneloop cells verses earlier generation Sanyo eneloop cells?
[A] On paper, newer generation offers longer cycle life and lower self-discharge rate. In practice, however, you’ll see no difference since they all have the same capacity. The difference in charge retention rate and cycle life may become noticeable after ~10 year, if at all.

[Q3] Is there any physical difference between PRO and standard version of eneloop cells?
[A] The PRO cells are slightly thicker, with diameter of ~14.4mm (verses ~14.1mm). So they may not fit if your appliance’s battery compartment is too tight-fitting.

[Q4] What is the difference between 'Pre-Charged', 'Hybrid', 'Stay-Charged', 'Active Charged', 'Ready to Use' and 'Ready to Go'?
[A] Those are all marketing terms for Low-Self-Discharge (LSD) NiMH batteries. Sanyo first used the term 'Pre-Charged' for Sanyo eneloop back in 2006. The latest Panasonic eneloop says “Ready to use” on each cell.

[Q5] I see a lot of other brands of rechargeable batteries advertised as Pre-Charged. Are they just as good Panasonic eneloop?
[A] In general, NO. Sanyo/Panasonic eneloop is still the best in terms of charge retention rate and cycle life. Many lesser-known brand also claim to have low self discharge rate and high cycle life just like eneloop. But based on my testing, none actually delivers.

[Q6] What about the AmazonBasics Pre-Charged Rechargeable Batteries?
[A] To clarify, there are three different versions of AmazonBasic rechargeable NiMH batteries:
- The original AmazonBasics AA NiMH Pre-Charged Rechargeable Batteries came in black wrappers. They are made in China and have the capacity rating of 2000mAh. They are NOT as good as Sanyo eneloop batteries.
- The second version of AmazonBasics Pre-Charged Rechargeable Batteries came in white wrappers. They are made in Japan and also have the capacity rating of 2000mAh. They appear to be rebranded 2nd-gen eneloop.
- The third version is also black but called AmazonBasics High-Capacity Pre-Charged Rechargeable Batteries. They appear to be rebranded eneloop PRO. They are rated 2400mAh, but actual capacity is around 2550mAh.

[Q7] How do the Duracell Ion Core pre-charged Batteries compare to eneloop or AmazonBasics cells?
[A] The Duracell 'ion core' AA cells appear to be rebranded eneloop PRO AA cells, while the Duracell AAA cells are most likely rebranded 2nd-gen eneloop AAA.

[Q8] My Panasonic eneloop AA batteries say '1900mAh' on them. Are they counterfeits?
[A] All standard eneloop AA cells (from original to 4th gen) are rated "Typical 2000mAh, Minimum 1900mAh". The confusing part is that 2nd-to 4th-gen eneloop AA cell have "min.1900 mAh" printed on it, even though the actual measured capacity is typically over 2000mAh.
For AAA cells: Standard eneloop are rated "Typ 800mAh, Min 750mAh".

[Q9] How do I find out the manufacture date of my new eneloop cells?
[A] Each eneloop cell has a date code embossed on it. Shine a strong flashlight from the side and slowly rotate the cell to find it. Date codes are in the form of YY-MM. For example, if it says '12-08' that means Aug 2012.

[Q10] Date codes on my new eneloop cells indicate they are made in 2012. Should I return then for newer batteries?
[A] Relax! Unlike ordinary NiMH cells, Sanyo eneloop are still perfectly good even after 10 years in storage. Once you recharge them, they will return to 100% capacity again.

[Q11] I just received some new eneloop batteries. Do I need to recharge them before use?
[A] You can use them right out of the package. However, standard eneloop cells are only charge up to ~75% when they left factory (High-capacity version usually just ~50%), So you can use a Smart charger to 'top-off' their charges. Do NOT do this with a Dumb charger because it will badly over-charge them.

[Q12] I thought I have to drain my batteries completely before recharging them?
[A] This is only necessary if you are using a timer-based dumb charger. With a smart charger, you can top-off your batteries anytime.

[Q13] Can I use other brands of chargers to recharge Sanyo eneloop batteries?
[A] Sanyo eneloop batteries can be recharged using any good-quality Smart charger designed for NiMH cells. But for longer battery lifespan, avoid ultra-fast (15- or 30-minute) chargers and Dumb (overnight) slow chargers

[Q14] What is the difference between 'Smart' and 'Dumb' chargers?
[A] A Smart charger monitors the voltage profile of each cell individually during charging, and stops when a charge-termination signal (negative delta-Voltage) is detected. This is the only way to avoid over-charging. A Dumb charge relies on safety timer to stop charging, or has no termination mechanism at all. This usually results in over-charging which is bad for battery lifespan.

[Q15] How good is the Sanyo MQN06 charger bundled with most older eneloop packages?
[A] The MQN06 is semi-smart but has two issues: it charges in pairs (monitors the combined voltage of two cells), and the charging current is only 300mA. That means it take about 7 hour to recharge a pair of eneloop AA cells. A better choice is the Panasonic BQ-CC17 which charges each cell individually (but still at the same 300mA current)
[Note: Charge time (hour) = Capacity (mAh) / Current (mA) ]

[Q16] What is the best charging speed for eneloop cells?
[A] Choose a charger that gives you charge time between 2-5 hours. That means charging current of 400-1000mA for AA, 200-500mA for AAA..

[Q17] Isn't it true the best charging speed for NiMH and LSD-NiMH battery is the slowest?
[A] That’s only true when using a dumb charger which blindly charges for 12-15 hours, so the current has to be below 0.1C (200mA for a 2000mAh cell) to avoid over-heating. For a smart charger, the current needs to be at least 0.2C to ensure proper termination. If the charging current is too low, the negative delta-V detection may not work reliably. (The BQ-CC17 is an exception since it uses pulsed current)

[Q18] I always keep a set of ordinary NiMH batteries in the charger to keep them freshly charged. So why do I need low-self-discharge batteries?
[A] You don't need to do that with LSD cells. Just charge up a spare set ahead of time and keep them in your drawer. Swap them in whenever needed, just as how you use disposable cells.

[Q19] Why should I buy those 2000mAh eneloop instead of regular NiMH batteries that are rated 2700mAh or higher?
[A] All rechargeable NiMH AA cells rated 2700mAh or higher are susceptible to rapid-self-discharge problem. Beware of off-brand batteries that claim '3000mAh' or higher. Most of them can't even deliver 2000mAh.

[Q20] Can I use eneloop in places with extremely hot or cold weather?
[A] As a rule of thumb, every 10 degree C rise in temperature causes the battery's self-discharge rate to double. So although your eneloop cells can still function correctly, their shelf life will be reduced at high ambient temperature.
For cold weather it is not a problem, since eneloop cells are rated down to -20 degree C.

[Q21] Should I store unused eneloop batteries in the refrigerator to extend their shelf life?
[A] For ordinary NiMH cells, storing them in lower temperature greatly reduces their self-discharge rate so you can get longer shelf life. For eneloop cells it is not worth the trouble, because they can be stored for years at room temperature.

[Q22] Can I use eneloop batteries in cordless phones?
[A] Yes - as long as your phones (such as Panasonic DECT 6.0 cordless phones) are using individual AAA cells, instead of battery packs with special connectors.

[Q23] Do rechargeable batteries only go bad after they meet the number of charging cycles, or their lifespan is limited by time also?
[A] Capacity of a NiMH cell gradually deteriorates with number of discharge cycles. The 'lifespan' claimed by manufacturer is the number of deep-discharge cycles before capacity drops to 50%. This is done under tightly controlled test conditions, so in real life your result may vary.

[Q24] When rechargeable batteries go bad, do they also spill chemicals (like alkaline cells) or just won't hold a charge?
[A] Good-quality NiMH cells do not spill electrolyte as they gradually deteriorate. The only chance this can happen is when they are (a) severely over-charged at a high current, (b) severely over-discharged, or (c) exposed to extreme heat.

[Q25] My baby swing calls for 4 D sized batteries. Do eneloop D spacers work well?
[A] You can use those in a pinch, but expect to replace/recharge your AA cells a lot more frequently than before. This is because the energy stored in an alkaline D cell is about 7-10 times greater than that in eneloop AA cell. See my following review for other options: Panasonic BQ-BS1E4SA Eneloop D Size Spaces

[Q26] My La Crosse BC-700 Battery Charger reports some eneloop batteries as 'null'. Are they defective?
[A] If a battery is over-discharged and its voltage drops below 0.5V, the La Crosse charger cannot detect it and so the display says 'null'. Charge your 'null' battery in a dumb charger for a few minutes, then the La Crosse charger will recognize it.

[Q27] Is the La Crosse BC-700 better than the Panasonic BQ-CC17?
[A] Each has its advantages. The BQ-CC17 is inexpensive, simple to use, and works great for daily charging.
The BC-700 is an Advanced charger. It allows you to determine the true capacity (mAh) of all your batteries, and to revive those under-performing cells. Then you can group cells with similar capacities together for best result. See my "BC-700 FAQ" for details:
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TOP 100 REVIEWERon April 18, 2015
The eneloop Pro follows the long-standing eneloop tradition of NiMH batteries that run circles around most of the competition. This eneloop Pro battery is NOT designed for general usage, but rather high-drain applications. When paired with these high-drain applications, the Pro excels in a fashion that few other batteries can, giving you performance that other NiMH rechargeable and disposable alkaline AA batteries cannot provide.

Eneloop is considered by many to be the tour-de-force of rechargeable NiMH cells (much like Panasonic is with lithium ion cells.) Gone are the days where NiMH cells did not give performance that came even close to alkaline. Things like memory, low service lives, rapidly fading capacity, etc. are over. Today we have NiMH cells that can dramatically outperform the finest of disposable alkaline batteries and can be charged thousands of times. Over a 10+ year period, you can save thousands of dollars with a good NiMH setup.

The eneloop Pro is eneloop’s (formally Sanyo and now Panasonic) follow-up to their highly successful eneloop XX series. Like the XX, the eneloop Pro is a SPECIALTY battery. It is NOT intended for usage with lower drain applications, and performs poorly when used for this purpose. However, when used in high-drain applications that tend to be brutal on the battery, the eneloop Pro gives unparalleled runtime that no alkaline can come even close to.

THE STANDARD ENELOOP 2100 VS THE ENELOOP PRO: Which is right for you?
Eneloop’s newest innovation is 4th generation NiMH cells. Like previous generations, eneloop is offering a standard-use and a high-drain model. These eneloop Pros use 4th gen technology, as do the standard eneloop “2100”. This fourth gen technology gives both batteries a very wide operating temp range, improved stability in output, slower self-discharge, and increases in durability.

Eneloop Pro SPECS:
-Capacity: 2550 mAh
-Service Life: up to 500 recharge cycles
-Rate of self-discharge: about 85% capacity remaining at 1 year of storage

Eneloop 2100 SPECS:
-Capacity: 2000 mAh
-Service Life: up to 2100 recharge cycles
-Rate of self-discharge: Over 70% capacity remaining at 5 years of storage
-A substantial performance improvement with high-drain devices vs. the third gen

THE 2100 --- The standard eneloop 2100 is designed to be a high-capacity battery that is capable of handling all but the worst of high drain devices. This battery makes substantial improvements over the third generation when it comes to handling higher-drain devices. It is ultra-low discharge (literally now it discharges SLOWER than many disposable batteries!) and high capacity at about 2000 mAh. This battery works great in both low drain and high drain apps. Additionally, with a cycle life of 2,100, this battery has serious longevity (literally the service life is four times that of the XX or Pro.) Because of this, most household devices should use this standard eneloop 2100. While it has a lower capacity than the eneloop Pro, the slower self-discharge and the ability to work better with low-drain devices will give better performance than the Pro with most devices. So if you are not using a device in which you constantly have to switch batteries out, the 2100 is what you want. The picture I uploaded shows a basic remote and Logitech wireless mouse; those devices get the best performance from the 2100s because they are not high-drain devices and so I use them exclusively in those devices.

THE PRO --- However, there are some devices that are just plain brutal on batteries. These will benefit greatly from the Pro (or XX) design. For example, in my picture you can see a Fenix LED flashlight and a wireless gaming mouse. These devices put a world of hurt on batteries and run times are measured in hours. The eneloop Pro makes substantial improvements over the already outstanding 2100 in this sort of application. Cameras, audio players, high-output flashlights, medical devices, lasers, etc. will benefit here.

So which battery you need completely depends on your application. I own 4 XXs and 4 Pros to go along with about 20+ 2100s. I use my 2100s for standard applications, and the XX or Pro for high-drain devices.

Like eneloops of the past, one thing that makes the brand unique is their advertising. Many battery makers advertise their batteries as having a MUCH higher capacity than they actually do. For example, I purchased 2500 mAh Tenergy batteries and brand new they only had a capacity of about 1700 mAh, and then rapidly shrank from there. I have had similar experiences with both Duracell and Energizer rechargeable cells. Eneloop guarantees each and every battery will meet their minimum mAh rating, and as a general rule all batteries exceed these ratings by a substantial margin. With these Pros, I purchased a 2550 mAh battery and I got a 2550 mAh battery. Additionally, eneloops do not rapidly shrink in capacity like other brands. Fives years or ten years down the line, these batteries will still work great if cared for. This longevity makes eneloop a much better value than inferior NiMH cells: spend a few extra bucks on eneloop today and enjoy their superior performance for years to come while simultaneously saving money.

Eneloop also sends their batteries pre-charged (and they were charged by solar energy.) With the low self-discharge of the Pro, and the extremely low self-discharge of the 2100, you can use these batteries immediately after purchasing them.

While the third generation batteries did a great job with colder temperatures, these 4th generation 2100s and Pros are outstanding. If you want to keep a flashlight in your car, these batteries are hard to beat given they work well in both hot-hot and cold-cold, and temperature extremes will not wreck your service life.

Ultimately, there are two things I like about this battery the most. One, I save a ton of money over disposable batteries. I am talking thousands of dollars while simultaneously supporting environmentally friendly technology. Two, I get better performance from these eneloops and can use my devices longer. As of mid-2015, this is really THE battery to have for your high-drain devices (and the eneloop 2100 is really THE battery to have for your general-use devices.) So I highly recommend the eneloop Pro, as do I recommend the eneloop 2100 and eneloop as a company.

If you are looking for a battery that gives you optimal performance with your high-drain devices, but would prefer an alternative to expensive lithium disposables, the eneloop Pro is the balanced choice of outstanding performance, outstanding value, and outstanding longevity. There really is no substitute.
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on February 26, 2015
Note: This review is based on the AA variant of the eneloop pro

I made a comment in my review of the regular eneloops that it was a hair thicker than regular alkalines. Devices with extremely tight-fitting battery compartments may face an issue using the regular eneloops. The eneloop pros perform even worse in this regard; they are yet another hair thicker than the regular eneloops.

Devices with formerly little or no issue with the eneloops now face a variety of situations with the eneloop pros. Removal of the batteries from the battery compartment of the Xbox 360 wireless controller, for instance, became next to impossible without some ingenuity. Cursor movements with the Microsoft Wireless Mouse 5000 became sluggish due to the ever-so-slight protrusion of the battery cover, creating extra friction with the table surface.

Panasonic should have put a discretionary label informing users of the additional thickness between the eneloop and the eneloop pro. Unless you're certain of the battery slot tolerances of your appliances, save yourself the frustration and get the regular eneloops instead.
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on December 26, 2014
I purchased 8 of these batteries to use on my Nikon SB-600 Flash. Previously I had been using both Duracell and Energizer brand rechargeable Ni-MH batteries. The differences are night and day. The envelop pro batteries allow me to shoot 3 fps with my flash for 2-3 seconds before they can't keep up. In the past, I was lucky to get my flash to cycle in time to go off for every other shot.

I also use the current generation of standard eneloop rechargeable batteries on various gadgets and toys around my house. I would not recommend the :envelop pro" batteries for everyday use, not because they would not work, but because there is no need for a battery of this caliber for most things.

I will never go back to using any other type of rechargeable battery.

I use a La Crosse Technology BC-700 to charge the batteries and have never had an issue with heat dissipation.
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on May 26, 2014
This review is only for the AA "Eneloop Pro" batteries, as I did not purchase the charger combo. For starters, these batteries are rated 2450-2550mAh. I charged them up at 800mA (and I do not recommend this charge rate as it heated up the batteries too much, possibly due to peak detection problem), let them cool, popped them into my flash, and used it for one day. Their remaining capacity was about ~1400mAh, after a discharge to ~.89V per cell. I then discharged them again to the same ~.89V at a 400mA discharge rate, as I didn't monitor the first discharge and wanted to make sure the task was completed. I then charged them at a 400mA rate for 6:50-7:02 (hours:minutes) in an individual cell charger. Their capacities were a remarkable 2818, 2719, 2762, 2770 mAh. There seems to be a bit of variance, but the capacity is rather high. I will try to include a picture.

Updated: 2015-02-03 Discharge capacity was determined while using the discharge feature. Actual capacity after 8 months of usage ranged between 2380-2429mAh. A picture will be added.
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on June 10, 2014
I now have 28 of the Eneloop XX AA batteries. I use them in every thing from remote controls to a digital camera. I use them in a Nitecore EA8 900 lumen searchlight, a game camera and other flashlights and cameras. I have never had a single complaint or problem with them. Some I have had for 3 years and are still holding 2600 mAh and some as high as 2700 mAh. Panasonic now owns Sanyo and the newest AA batteries look a little different, but have more capacity (it says). The package states they're minimum capacity is 2450mAh and the old ones 2400mAh, however I have never had one with a capacity below 2600mAh.
I bought a La Crosse BC-500 to use in a car with solar cells as it is the only La Crosse that can be used this way, with a 12 v plug included. This one tells me the capacity of each battery. I recently bought a Titanium Innovations MD-1600L charger that can also has a car 12v plug and has 2 usb plugs so I can charge phones, tablets, iPods and such at he same time I'm charging 1 to 16 batteries.
If your going to be using rechargeable batteries, get a smart charger so they will last a very long time. Chargers that use a timer, such as those that come in a package with the batteries, will eventually damage them and/or the batteries will not last very long at all. Heat is what kills these batteries.
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on January 30, 2015
Right off the bat these batteries excelled in reaching their capacity in one shot, here are the stats for the cells (tested them in both the La Crosse and Maha C9000)

Discharge 300mAh: Maha C9000
Batt 5 - 872mAh / 3:12
Batt 6 - 875mAh / 3:14
Batt 7 - 875mAh / 3:13
Batt 8 - 865mAh / 3:10

Discharge - 250mAh: La Crosse BC-1000
Batt 1 - 896mAh / 3:36
Batt 2 - 904mAh / 3:38
Batt 3 - 913mAh / 3:40
Batt 4 - 907mAh / 3:39

Both sets seem to do well, though the Maha seemed to be pushing the cells in the 1.1 volt range instead of the 1.2 range. I have yet to determine whether 300mA discharge was too much or they were not completely charged, though they should have been charged (see my review on the Maha charger for more details). I often hear people are not getting fully charged (or drained cells) and i wanted to clarify a few reasons why that might be. EIther you are using it in a device that does not work well with NiMH rechargeables or the cells are over a year old and may need a refresh before using.

Which brings me to my next point, these cells were manufactured in January of 2014 and (well you can see when i wrote this) it's now 2015. So naturally i am guessing the reason the extra 50mA current pushed the cells voltage further down with the Maha charger (since the La Crosse was fixed at 250mA discharge from choosing 500mA as the charging rate on both chargers). So while these cells are precharged, they are generally only charged to about 70% and after being a year or so in storage they start to lose their vibrancy and often times a simple charge, discharge and recharge is in order. Certainly you can use these cells out of the package and they should work fine, however the older the cells are the less charge they will have in them during obtaining them.

I am also glad to see that the package these cells came in was in good condition. There's been a few folks out there (including me) who has got Eneloops that has escaped out of the package either during shipping or they were shipped in that condition. It's not good for cells to be out of the package and can cause the batteries to short circuit depleting their life. There are other factors that could reduce the charge levels by environmental factors during the production to when they get to your home and with a few folks that have done tests, these batteries can be low as 40%. My particular cells seemed to be around 65% capacity. So even though these cells have been labeled as precharged, the capacity is not generally at 100% capacity and functioning 100% right from the package. These batteries do hold their charge for a long time and i wouldn't expect them to die at 3 years in storage. They may not have as much capacity as those HSD cells but often times you are sacrificing cycles for extra capacity.

These cells (both AA/AAA's) offer the best of both worlds. I use these for emergencies when my regular Eneloops are discharged and i got no alkalines available. One thing i will note if you use these cells 3x out of the week (that's discharging and recharging) you can probably get 4-5 years out of them. You can get more cycles out of them if you recharge them at 1.26 volts instead of 1.20 volts. So if you use these in regular applications you may want to think about recharging them on a regular basis (depending on how much you use them) and for low drain devices, regular Eneloops would be a far better idea. I use my older cells for low drain devices so my newer regular Eneloops gets used in the high drain devices. But if you are light with these you should get 5+ years out of them. As i stated earlier, i prefer using regular Eneloops for daily usage as those cells will outlast these, but for high drain critical applications these cells (both the AA/AAA) are excellent.

Also if you see rechargeable AA Duracells with the mAh capacity of 2400, those are similar (or the same) as the AA Eneloop Pros.
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I have tested a set of those new Sanyo Eneloop 2500 XX Batteries, because they claim to be pre-charged like the original Sanyo eneloop, but have a much higher capacity of 2500mAh (compared to just 2000mAh). Here are my findings using the La Crosse BC-900 battery charger/analyzer:

- Right out of the package, the average remaining charge was 1004mAh, or just 40% of the rated capacity. The spread is very tight (990-1019mAh), which means they are indeed LSD type. Note that just like the original eneloop, those XX cells were not fully charged when they left factory,

- After just one Charge/Discharge cycle, the average capacity jumped to 2602mAh! Next cycle improved this number slightly to 2607mAH. Again the spread is very small (2570-2650mAh), indicating a good quality control.

Just for comparison, here are some of my test results for other LSD cells:
SANYO New (1500-cycle) eneloop AA: Rated 2000mAh, tested ~2100mAh
GP Recyko NiMH AA: Rated 2100mAh, tested ~2230mAh
IMEDION AA: Rated 2400mAh, tested ~2450mAh

Some additional technical details printed on the Sanyo XX package:
- "Typ. 2500mAh, Min. 2400mAh" (The original eneloop claims "Typ. 2000mAh, Min. 1900mAh")
- "Recharge up to 500 times" (The original eneloop claims 1000 cycles, second-gen eneloop claims 1500 cycles)
- "Retains 75% of the capacity after 1 year of storage at 20 degree C" (The original eneloop claims 85%)
- "Suitable for temperature as low as -20 degree C" (The original eneloop calims -10, second-gen claims -20)

One important note: the Sanyo XX cell is _slightly_ thicker than the original eneloop cell. This may prevent you from using the XX in appliances with very tight battery compartments.

About the 'Free' battery holder: It can hold either 4xAA cells, or 4xAAA cells + 1xAA cell. It is handy to have but nothing to get too excited about. I consider it worth paying one dollar for.

Bottom Line:
The new Sanyo XX cells really do offer the highest capacity among all LSD cells I have tested. Its capacity is comparable to that of ordinary 'high-capacity' NiMH cells, so you get the best of both worlds. On the down-side, it is currently priced about 2x higher than the lower-capacity Sanyo eneloop. So you should only use them for mission-critical applications, where both low self-discharge and high capacity are required.

For most less-demanding applications, you may consider getting TWO sets of Sanyo eneloop for the price of one set of those XX cells. Keep the extra set as spare, and swap it in as the first set goes to the charger. That way, you'll never be caught without fresh batteries.
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on January 29, 2015
I purchased the previous generation of the Eneloop rechargeable batteries, in 2013, after doing much research into the best rechargeable batteries. I have not been disappointed. Since I needed more batteries, I did some additional research, and found out they had a newer version, which is supposed to be even better. So far, so good.
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on December 8, 2011
The measurably higher capacity and shelf life of these batteries is well documented, and commented about, elsewhere, so I will simply confirm that they are great performers. The main thing I would like to mention here is their size. I first tried the white AA Eneloops, and found (as did many other reviewers) that the diameter was slightly larger than standard AA batteries, to the point where they were actually unusable in one device I have. These black XX Eneloops seem to have come back within the AA size spec., and fit nicely into the device where the white ones would not.

Addendum/clarification: While I haven't taken a set of calipers to these batteries, I can tell you this ... I own a device (a wireless guitar transmitter made by "Line 6") where the battery compartment is simply two holes bored straight into billet aluminum. A brand new set of AA alkaline Duracells will slide into those holes easily, as will any of the four black XX Eneloops purchased here, but with no room to spare. I have 8 of the white Eneloops, that I purchased at Fry's electronics, and I believe to be genuine based on comparison checks of features provided by other reviewers. Not one of the those 8 white AA Eneloops will slide into the hole where the black XXs and standard alkaline AAs will. Also, dozens of reviewers of the white Eneloops complain of the same problem, "the white AA Eneloops are thicker than standard AAs" ... these black XXs are not.
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