eneloop XX 950mAh Typical / 900mAh Minimum High Capacity 4 Pack AAA Ni-MH Pre-Charged Rechargeable Batteries
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The 4HR-4UWX AAA rechargeable batteries utilize eneloop XX technology, delivering 950mAh of long lasting performance for high power applications. XX batteries are the perfect choice for powering high
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I tested four of those cells, using my old La Crosse BC-900 Battery Charger.
- Right out of the package, their average remaining charge is 1568mAh, or nearly 80% of the rated capacity of 2000mAh. The spread is also very small, from 1558 to 1577mAh. This proves that they are indeed low-self-discharge type. (Date code on my cells says "11-01", or Jan 2011)
- After one recharge/discharge cycle, their average capacity improved to 2115mAh
- After two more recharge/discharge cycles, their average capacity leveled off at 2133mAh, or more than 6% higher than the rated capacity.
The above results are very consistent with what I have previously observed, while testing second-gen eneloop cells in the Costco package. Therefore I'm convinced that those are indeed genuine second-gen Sanyo eneloop cells. (See the scans I uploaded to Customer Images section, if you need to distinguish between old and new eneloop cells)
On the other hand, currently the prices of those new eneloop cells are about 25-50% higher than that of the original eneloop cells. So one may question: do the new eneloop cells offer sufficient improvement over the old, to justify the price different? Let's compare the following factors:
- Cycle Life: The 2nd-gen eneloop claims to "recharge up to 1500 cycles", while the original only claims 1000 cycles. This 50% improvement looks great on paper, but note that if you recharge your eneloop cells twice every week, it will take 10 years to reach 1000 cycles. So in real life, most average users will never notice the difference.
- Self-Discharge Rate: The new eneloop cells claim to "maintain 75% charge after 3 years", while the original only claims "80% after 2 years". Again, in real life most people will never notice the difference.
- Capacity: First-gen eneloop AA cells have "Typ 2000mAh, Min 1900mAh" printed on them, while 2nd-gen eneloop AA cells only say "Min 1900mAh". But in fact they have the same capacity rating of 2000mAh (typical) according to official Sanyo web site. My measured capacity numbers are actually around 2100mAh for both versions.
Both the new and old eneloop cells are excellent products. You can safely mix and match them in any application, and probably nobody can tell the difference in the next 10 years. But in case you can't decide which version is a better value... Just flip a coin and pick one - you can't lose either way!
[Update on July 31, 2011]
Long term self-discharge data: I have tested a pair of new eneloop AA cells after 104 days sitting on the shelf (the batteries, not me). The average remaining charge is 88.7%. This charge-retention rate is slightly better than that of the original eneloop, but the difference is within margin of error for my experiment.
[Update on May 8, 2012]
Nowadays the 2nd-gen eneloop cells are generally priced lower than the original. So you should definitely get the newer version.
[Update on Apr 7, 2013]
Long-term self-discharge rate update: I just tested a set of 2nd-gen eneloop AA cells after two years in storage. They retained 1685mAh, or 84% of rated capacity. This is no difference from the claimed charge retention rate of 3rd-gen enellop (which says 85% after two years). See my following review on 3rd-gen eneloop:
[Q1] My Sanyo eneloop AA batteries say '1900mAh' on them. Are they counterfeits?
[A] All eneloop AA cells (both original and second-gen versions) are rated for "Typ 2000mAh, Min 1900mAh" according to Sanyo. The confusing part is that 2nd-gen eneloop AA cell only has "Min 1900mAh" printed on it, even though the actual measured capacity is close to 2100mAh.
Simialrily, eneloop AAA cells are rated for "Typ 800mAh, Min 750mAh".
[Q2] Date code on my new eneloop cells says '10 01' (Jan 2010). Should I exchange them for newer batteries?
[A] Relax! Unlike ordinary NiMH cells, Sanyo eneloop are still perfectly good even after 5 years in storage. Once you recharge them, they will return to 100% capacity again.
[Q3] 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. Rayovac used 'Hybrid', and so on.
[Q4] 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, eneloop cells are only charge up to ~75% when they left factory. 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.
[Q5] 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.
[Q6] 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
[Q7] 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.
[Q8] Should I stick to the Sanyo MQN06 charger packaged with most Sanyo 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. Better choices include Sony Cycle Energy BCG34HLD and iGo 4-Position Charger.
[ Note: Charge time (hour) = Capacity (mAh) / Current (mA) ]
[Q9] What is the best charging speed for Sanyo eneloop?
[A] Choose a charger that gives you charge time between 2-5 hours. That means charging current of 500-1000mA for AA, 200-500mA for AAA.
[Q10] Isn't it true the best charging speed for NiMH and LSD-NiMH battery is the slowest?
[A] That is 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.
[Q11] I always keep a set of ordinary NiMH batteries in the charger to keep them freshly charged. So why do I need LSD cells?
[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.
[Q12] Why should I buy those 2000mAh Sanyo eneloop instead of ordinary NiMH batteries that are rated 2500mAh or higher?
[A] All rechargeable NiMH AA cells rated 2500mAh or higher are susceptible to Rapid-self-discharge problem. Beware of off-brand batteries that claim '2900mAh' or higher. Most of them can't even deliver 2000mAh.
[Q13] Can I use eneloop in places with extremely hot 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.
[Q14] 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 hardly worth the trouble, because they can be stored for years at room temperature.
[Q15] 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.
[Q16] 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.
[Q17] 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, or (b) severely over-discharged, or (c) exposed to extreme heat.
[Q18] 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: SANYO Eneloop Spacer Packs with 2 AA with 2 D-Size Spacers
[Q19] 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.
[Q20] I read on Wikipedia that there is an Eneloop 3rd generation battery (HR-4UTGB.) Are they worth getting over second generation?
[A] Panasonic (who bought Sanyo in 2009) claims that lifespan of 3rd-gen eneloop cells has been upgraded from 1500 to 1800 cycles. But keep in mind that even if you recharge your cells twice every week, it will take you nearly 15 years to use up 1500 cycles from your 2nd-gen eneloop cells.
[Q21] Are the new AmazonBasics Pre-Charged Rechargeable Batteries just rebranded 1st-gen eneloop cells?
[A] Not exactly. According to their mechanical features, they are most likely SECOND-gen eneloop cells. See my review for details: http://www.amazon.com/review/RLX50IR99K7PL/
[Q22] How do the new Duracell pre-charged Batteries ('2400mAh', 'Long Life Ion Core') compare to Sanyo eneloop or XX cells?
[A] Based on my testing, I believe the Duracell 'ion core' AA cells are actually rebranded Sanyo XX AA cells, while the Duracell AAA cells are rebranded 2nd-gen eneloop AAA.
[Q23] Amazon product page now says "There is a newer model of this item" and points to Panasonic BK-3MCCA8BA eneloop AA 2100 Cycle Batteries. Should I get that one instead?
[A] The 4th-gen eneloop (now marketed under Panasonic brand name) is identical to 3rd-gen except for the advertised cycle lifespan. However, the new Panasonic BQ-CC17 charger is better than the old Sanyo MQN06, because it charges each cell individually. See my review on it for details:
I would have rated the product a whopping 5-stars except for having to exert that necessary force to complete the mission of inserting a too large thing into a little-too-small opening. Though I have had decades of practice with that operation this particular evolution in this exact circumstance is new to me.
And I am grooving on having a portable radio with a built-in battery charger that automatically charges the batteries when I plug it into 120-volt current. The radio plays while charging and the charging mode ends automatically when the batteries are topped off. This radio is smarter than I am.