Customer Reviews

Sanyo Eneloop 2-AA NiMH Pre-Charged Rechargeable Batteries with USB Charger

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[Updated Oct 24, 2008]
My original review on the Sanyo eneloop NiMH cells was written nearly two years ago. Since then, I have learned a lot more about the characteristics about eneloop and other low-self-discharge cells. So it is time to clear up some inaccurate information I wrote about eneloop's self-discharge rate.

1. I was told that the Sanyo eneloop cells were not 100% fully charged when they leave factory. This makes sense because new cells are fast-charged in the factory to save time. In order to avoid problem with heat and gas built-up, they cannot be charged to 100%. I have tested some eneloop cells that were manufactured 20 months ago, and they still maintained about 70% charge. On the other hand, cells manufactured 6 months ago contain about 75% charge. This confirmed that the discharge rate is much lower than I previously estimated.

2. The self-discharge rate of eneloop (and other LSD cells) is not linear! My own testing showed that a fully charged eneloop may lose 10% of its initial charge during the first month of storage, but in the second months it may lose just 2-3%. The rate becomes even slower after three months. In fact, my 5-month self-discharge test using various brands of LSD cells gave nearly identical results as my previous 3-month test.

3. When an eneloop cell is freshly charged, its capacity actually measures at about 5% higher than its rated capacity (2100mAh vs. 2000mAh). In my previous tests, I used measured capacity as base to calculate the percentage loss. This results in apparently higher percentage loss. Had I used the rated capacity as base value, the self-discharge rate would be about 5% lower.

Based on the above revelation, I believe Sanyo's claim about eneloop (maintain 85% charge after one year, 80% after two year) to be accurate. Therefore the title of my previous review ("The News of LSD Has Been Slightly Exaggerated") has to be replaced.

Over the past two years, I have tested several different brands of LSD cells available from Amazon.com, including Rayovac Hybrid, Kodak Pre-Charged, and Duracell Pre Charged. They have all performed very well - practically no difference from the Sanyo eneloop. So the bottom line is: just pick which ever brand of LSD cell is on sale, and you can't go wrong.


[Update on April 21, 2011]
- After testing and using various brands of LSD cells over the past four years, Sanyo eneloop cells have proven to be the most reliable and consistent of them all. I now have to recommend Sanyo eneloop over all others brands.

- Recently Amazon started to offer the SANYO NEW 1500 eneloop cells, at around 25% higher price. In my testing, the improvement of the new eneloop over the original is hardly noticeable. So you'll have to decide whether it is worthwhile to pay the extra cost.

[IMPORTANT NOTE]
My original review below was written back in 2007, when the Sanyo eneloop first became available
through Amazon.com. Part of my initial estimation about eneloop's self-discharge rate turns out to be inaccurate. Please see my other Amazon spotlight review for updated information.

[Original Review follows]

According to Sanyo, the new eneloop LSD (low self-discharge) NiMH batteries can maintain 85% of its original charge after 1 year of storage. This claim is slightly misleading, because it is based on simulation test at 20 degree C. At higher temperature, the self-discharge rate is likely to be much higher.

I have tested five of those AA cells (details are given in my review for the eneloop 4-pack). The average energy loss is about 26% after less than 6 months of storage, based on manufacturer date codes. This self-discharge rate is about 3 times higher than what Sanyo claimed. However, it is still 6 times lower than that of ordinary NiMH batteries. Therefore I'm in the process of replacing most of my existing rechargeable cells to the Sanyo eneloop.

Thanks to lower self-discharge rate, you'll discover a lot more applications for eneloop cells in your house, such as in clocks and remote controls. Do NOT use those cell in smoke detectors, since their discharge voltage profile is very different from that of alkaline cells. Also, don't use them as emergency flash lights batteries in your car, because the higher temperature during summer time will probably nullify the advantage of LSD.

[Update on Jan 13, 2007]
I have tested six new eneloop AAA cells, dated "2006-06'. The average residue charge is 589mAh, and the freshly charged capacity is 827mAh. This implies a self-discharge rate of 29% in 7 months, which is consistent with the rate for AA cells (26% loss in 6 months).

[Update on Jan 29, 2007]
The Rayovac "Hybrid" rechargeable NiMH batteries are now available at Walmart, priced at only $[...] for 4-pack of AA or AAA cells. It is also advertised to have low self-discharge rate, but not as low as that for eneloop. The eneloop is supposed to retain 85% charge in 12 months (when stored at 20 degree C), whereas Hybrid is supposed to retain 80% charge in 6 months (no mention of temperature).

[Update on June 3, 2007]
In my 2-month self-discharge test using four different brands of NiMH cells. Hybrid and eneloop came up neck-and-neck!

Room temperature: 60-62 degree F (16-17 degree C). All capacities measured are average of 2-cells.

- Sanyo eneloop 2000, purchased Jan 2007.
Initial capacity measured: 2070mAh
Capacity after 62 days: 1796mAh (-13.2%)
(Note: my previous result for eneloop showed -18%, but I repeated the test and it did better this time)

- Rayovac Hybrid 2100, purchased Jan 2007.
Initial capacity measured: 2155mAh
Capacity after 62 days: 1859mAh (-13.8%)

- LaCrosse 2000, purchased Jan 2006.
Initial capacity measured: 1902mAh
Capacity after 62 days: 1417mAh (-26%)

- SONY 2300, purchased Sep 2004.
Initial capacity measured: 2210mAh
Capacity after 62 days: 1309mAh (-41%)

So neither eneloop nor Hybrid did as well as advertised, but they are still significantly better than previous generation of NiMH cells. So you can't go wrong with either brand.

I received several sets of Eneloops in February and label told they were produced in April - so they sat at warehouse for nine month. I put them into camera and they worked just fine. Kudos Sanyo!
I should also mention that Sanyo includes reusable battery holders with each set of four. These holders do not look very sturdy, but they perfectly usable.

Technically, Sanyo solved the main problem with NiMh technology - frightening self-discharge rate (up to 40% a month for standard cells). By doing this Sanyo reduced cell capacity down to 2000 mAh from today's top line of 2700 mAh.

Simple calculation shows that due to self-discharge a good 2700 mAh battery holds only around 2000 mAh after a month and a half.
So the answer to the question "which battery is better - Eneloop or standard NiMh" - lies in the usage pattern.

If you always keep batteries in your camera in top-notch charged condition, then standard 2700 mAh set is a winner. For occasional shooters who always forget to charge batteries (like me), Eneloop makes lot of sense because in three month I get around 1900 mAh out of Eneloop and only 1400 mAh from the standard cell. So Eneloop is a winner for everyone who keep batteries inside the camera or any other device for more than 6 weeks.

And, well, if paragraph above looks too technical with too many details and numbers - then Eneloop is a clear winner too, because it just behaves the way battery should behave - without forcing users to know how it works.

This observation made me buy additional sets of AAA Eneloops to use in my wireless mouse, keyboard, voice recorder and LCD flashlight. It should be taken into account that Eneloops are four times more expensive than Alkaline cells, so it is reasonable to use them for devices that require fresh batteries at least twice a year.

This package, eneloop Compact Charger (includes 2 AA), contains the Sanyo 2-cell charger 'MDR02'. I use one in my office to recharge batteries for my MP3 players, headphones, wireless mouse, etc. It has served me well for the past 2.5 years with absolutely no problems.

The MDR02 works very well as a travel charger for my trips, too. It is tiny (measures only 3"x3"x1"), very light (weights about the same as two AA cells), and accepts universal input voltage of 100-240V AC. It is also a "smart" charger in the sense that it charges each cell individually, and stops whenever each cell is full.

The charging current of MDR02 is 550mA for AA, 380mA for AAA. That means it takes about four hours to charge up either 1 or 2 eneloop AA cells (2000mAh). This may seem slow, but it is actually a lot faster than the Sanyo 4-cell charger 'MQN06' included in Eneloop 4 Pack AA w/ Charger. The MQN06 charges at only 300mA, so it takes up to 7 hours for a pair of eneloop AA cells. It also forces you to charge in pairs, which is very inconvenient if your appliance requires odd number of cells.

If you need a faster, more advanced 4-cell charger for home use, I highly recommend either the La Crosse BC-9009 or BC-700. As a reminder: the eneloop cells do NOT require special chargers. Any good quality "smart" NiMH charger will do the job. The reverse is also true - You can use this eneloop charger for other brands of AA or AAA NiMH cells as well.

This compact charger, MDR02, is best suited for traveling, because it is tiny (measures only 3"x3"x1"), very light (weights about the same as two AA cells), and accept universal input voltage (100-240V AC). It is also a "smart" charger in the sense that it charges each cell individually, and stops whenever each cell is full.

The main drawback of this charger is that it is rather slow. The charging current is 550mA for AA , and 380mA for AAA. That means it takes about four hours to charge up a pair of 2000mAh eneloop cells. What if you need to charge up a set of four 2700mAh cells? That will take close to 12 hours! So you really should keep another faster charger for home use. Just remember that the eneloop cells do NOT require special chargers. Any good quality "smart" NiMH charger will do the job.

The reverse is also true - You can use this eneloop charger to charge other brands' AA or AAA NiMH cells. I keep one in my office just to charge up batteries for my MP3 players, headphones, wireless mouse, etc. And since I always keep a spare set of fully charged batteries, the longer charge time does not bother me.

I was initially skeptical when I bought these but figured it couldn't hurt. I needed a set for my Nikon SB-600 flash. The 2700 mAh Energizers I had performed just fine until they sat in the flash for a month, at which point I had to carry a spare set "just in case". I charged the Eneloops, placed them in the flash and had my first call a month later. They worked wonderfully. I went the whole evening without needed spares. I used them again two months later and got a solid hour or two before they were exhausted. They easily lasted 2-3x as long as the Energizers and where in the flash for 2x as long. All-in-all, they've performaed very well. They may not maintain 85% of their charge after one year at room temp (as one reviewer suggested) but they certainly "sit in the bag" far better than my others. I am slowly phasing out all my non-Eneloops as a result...

I bought these batteries for use with my Canon S2 digital camera. I was having trouble with typical nimh batteries because I would charge a spare pair of batteries for use when the main pair died. But I was finding that the ones I charged a few weeks ago would be almost fully discharged by the time I would swap them. This was really annoying and pretty much defeated the purpose of having rechargeables... I had to use alkalines instead. But this new so called 'hybrid'/low discharge technology finally solves this problem. Of course it does not solve it completely because these batteries still discharge over time... just a lot slower, but at least now I know I have a pair of batteries that are at least 80 percent or so charged when I swap them. This technology was actually developed by an small independent company and licensed for use with all the major battery companies now. For instance, Sony is also utilizing it in their new batteries now. To me, this demonstrates how well it works.

So how does it hold up in real life? Pretty darn well, actually. I noticed that these particular batteries last really long in my Canon S2. I haven't had the problem of charged batteries being totally discharged by the time I swap them anymore. So if you're having similar problems with your older Nimh batteries, I would recommend giving these batteries a try. But don't feel limited to this brand, there are many other brands utilizing this technology and I've used other brands with the same great results.

Tip: If you live near a Fry's Electronics, they have a nice selection of battery choices that utilize this technology.

Funny, everyone seems so thrilled about how they come charged out of the box. While this is nice and convenient, the bigger picture is *why* they can come charged out of the box: they discharge at a much slower rate than normal (NiMH) rechargeable batteries. If you use your battery-needing product often, you may not notice this, but for things you use sporadically, this is a godsend. No more coming home from vacation to find your TV remote control is dead. No more grabbing your digital camera after three weeks of not using it only to find it won't start up.

These batteries are, indeed, the best of both worlds: they have the power and reuse advantages of a good NiMH battery, but the slow steady discharge of an Alkaline disposable. Look no further -- this is the rechargeable you've been waiting for.

And if you had to guess, I'm happy with my first set and about to order more... :)

11/2006:
I was going to buy the LaCrosse or Maha MH-504FS after reading tons of reviews. I'm glad that I didn't and bought this instead. First, this charger (not sure about the 2 batteries version) is a smart charger which monitors and charges batteries individually just like the LaCrosse. It is not a dumb timer charger you get for $10 or less. You don't need to worry about quick/slow charges (like 504FS) because it uses pulse charge to charge at a speed that's not too fast to hurt your batteries. Second, this charger costs so much less compared to Maha and LaCrosse. Third, I used these eneloop batteries fresh from the package without charging and took over 200 pictures (about 50 with flash and a few movie chip) with my Cannon A540. I believe it can take more pics because NIMH batteries take few cycles of discharge/recharge to reach full capacity. Last but not least, these eneloop battaries are able to hold the charge when sitting idle for months. Unless you charge the normal nimh batteries the night before, they are no good even if they are 2600 high power ones. By the time you use them, they are only partially charged.

I would recommand you to buy a LaCrosse if you still decide to use the ordinary NiMH batteries because you will need to use the refresh function to get rid of memory issue and the LED to tell you how much charge is left after letting the batteries sit for days. (Oh, I forgot to mention that eneloop claims that it can recharge 1000 times without memory issue.) However, if you decide to use the eneloop, forget about paying extra for Maha or LaCrosse and the normal Nimh batteries and just use this amazing charger and awesome batteries instead.

6/2007 update:
I bought a new set of Rayovac Hybrid Batteries to see how these compare to Eneloop because they are cheaper. I put the fresh new Rayovac in my digital camera, it works. But when I put it in a LED flashlight, the LED has no light output at all. Later, I put my used Eneloop (after 200 pictures) in it. Guess what? The LED works! Well, you get what you pay.

These 2100 mAh rechargeables are better than 2700 ones - Why - because the regular but higher capacity ones lose charge so quickly, within 10 days they have less charge left in them than the "eneloop" type.
I had some doubts how they would perform in the real world - in particular, their peak current capability (which will determine how well they actually work in a digital camera). Turns out - they do better than the regular ones. While my 1600 mAh panasonics gave approx 40 - 50 shots consistently, the same digital camera now gives me approx 100 shots with these eneloops. Suddenly my mom's camera which "ate up battery very quickly" - has become a "great camera" from the battery change. If she's happy, so am I. Incidentally - the amazon price is also very good - you can also try getting the ones with a charger - this eneloop charger charges batteries INDIVIDUALLY. This is critical - no matter which charger you buy - get ones that charge batteries individually and not in pairs. Also remember to always mark your batteries, so you don't mix up charged and discharged batteries when charging them. I've found this to be a common problem with many users.