Update (11/7 6:00pm): Amazon is also offering a 4-pack of AAA eneloop Ni-MH Pre-Charged Rechargeable Batteries for a very low $9.99 Prime shipped.
Update (11/6 11:25am): Newegg has an 8-pack of POWEREX MH-8AAI-BH 2400mAh AA Rechargeable Batteries for $19.99. Coupon code EMCWWPF77 drops it down to $16.99 shipped.
Amazon offers a 4-pack of eneloop XX 2500mAh Rechargeable AA Batteries with 4 Position Charger for $20.99. It’ll ship free for Prime members (free trial), but all other buyers will need to spend another $14 (order two?) to get free shipping. As a pricing comparison, this set originally sold for $35 and today’s deal is the best price we’ve ever seen by $5. The new, Panasonic-branded set is currently selling for $30.
Eneloop XX rechargeable batteries come pre-charged and ready to use. Even after a year of going unused, eneloop batteries will maintain 75% of their charge. Expect to keep these batteries around for a long time since they can be recharged up to 500 times. Nearly 7,000 Amazon reviewers rate this set a spectacular 4.6 out of 5 stars.
I have done extensive testing on the original eneloop rechargeable batteries since early 2007, shortly after they were introduced in the US. I have also tested the blue second-generation eneloop cells from the Costco eneloop package back in 2010. But this is the first time I have seen second-gen eneloop in white wrappings being sold in the US. With so much talk about counterfeit eneloop going around, I was understandably cautious when I purchased those SANYO NEW 1500 eneloop 8 Pack AA Ni-MH Pre-Charged Rechargeable Batteries.
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.
BOTTOM LINE: 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: