Two year Eneloops

[Mr Happy]

I have some unopened Eneloops dated August 2006. Since it's just reached their two year anniversary, I opened the package and tested four of them.

Initial voltage: 1.296/1.296/1.296/1.296 V.

Initial charge on discharge at 500 mA: 1354/1348/1363/1339 mAh (average 1350)

Measured capacity from C9000 break-in cycle: 1956/1938/1954/1938 mAh (average 1947)

It's interesting to compare the charge out of the package with the 2008 Eneloops I tested, which averaged 1730 mAh. This suggests that Eneloops lose about 200 mAh per year in storage when starting out at 85-90% of a full charge. At that rate it would take them 8 or 9 years to become empty.

 

[LED_Thrift]

Will they gain a bit of capacity after a few cycles, and get closer to the 1730 mAh of the 2008 eneloops?

 

[TorchBoy]

Will they gain a bit of capacity after a few cycles, and get closer to the 1730 mAh of the 2008 eneloops?

Wanna try that again?

That 1730 mAh figure implies that 2008 Eneloops are being more than 75% charged.

 

[Mr Happy]

That 1730 mAh figure implies that 2008 Eneloops are being more than 75% charged.

Yes, the average capacity after a break-in cycle of the 2008 Eneloops was 1997 mAh. An out-of-package charge of 1730 mAh is about 87% of that. I'm guessing they were probably charged up to about 90% at the factory since they were nearly four months old when I tested them.

 

[kurni]

It's good to witness Eneloops performing well. Thanks for sharing, Happy

 

[Bones]

After the seemingly endless disappointments with the 'high capacity' NiMH cells, it's gratifying to see the Eneloops continuing to perform better than even the most optimistic expectations.

A further summary of Mr Happy's findings, again noting they are after a full two years in storage, and who knows what trials and tribulations endured in transit:

Voltage variation out of the package: None to three decimal places.

Average capacity out of the package: 1350mAh *

Capacity variation out of the package: .018%

Average capacity after one break-in cycle: 1947mAh **

Capacity variation after one break-in cycle: .009% ***

* This number might have been even higher had the discharge been done at 400mA rather than 500mA. The industry standard discharge to measure capacity is .2C, which is 400mA for the Eneloop.

** Although very good as they stand, there is a good probablility the capacity of these Eneloops will increase. There are credible reports of capacity increases right up to 100 cycles.

*** Albiet trivial to begin with, the percentage of capacity variation actually decreased by 50% after the break-in cycle, and it's based on a significantly higher average capacity.

It's also noteworthy that, after one break-in cycle, the average capacity increased from 1947 for the 2006 vintage to 1997mAh for the 2008. Although most likely attributable to the fact that they are simply fresher cells, it could also be partially attributable to the Japanese propensity to continually introduce incremental improvements in their products. Especially considering the 2008 Eneloop is physically smaller than the 2006. Remember, it was downsized in the latter part of 2006 to provide for a taller positive post.

Wahoo Eneloop...!

 

[JWP_EE]

In August 2007 I bought some Eneloop cells from Amazon. Since an 8 pack was $20 I also got 4 pack to get me over $25 for free shipping.
I opened and used the 8 pack but decided to hold the 4 pack. After reading this post I opened the pack and the date code is 06-08TL. If that means August 2006 then they 2 years old. I have no way of testing their capacity, but the open circuit voltage is 1.295/1.295/1.295/1.296V.
I am amazed they are within 1mv of your readings.

 

[TorchBoy]

Wahoo Eneloop...!

Assuming the LSD side of things hasn't suffered.

 

[Woods Walker]

Good to know Mr. Happy. I changed out my old standard batteries in my PT headlamp for the Bug out bag (ER aka bail out bag) with some LSD batteries as they will not leak. Nice to know if I don't use the headlamp for an extended time there the batteries will still work.