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Customer Review

1,786 of 1,822 people found the following review helpful
5.0 out of 5 stars LSD is great.... just keep away from heat!, January 8, 2007
This review is from: Sanyo Eneloop AA NiMH Pre-Charged Rechargeable Batteries - 8 Pack (Discontinued by Manufacturer) (Electronics)
[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.
http://www.amazon.com/review/R3TU586FEKG57A/

[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.
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Showing 1-10 of 111 posts in this discussion
Initial post: Jan 17, 2007 10:10:41 AM PST
If fresh-charged is sub-1000 mAh, then these aren't 2000 mAh cells, are they?

Posted on Jan 17, 2007 10:10:42 AM PST
[Deleted by the author on Jan 17, 2007 10:10:50 AM PST]

In reply to an earlier post on Jan 17, 2007 12:43:56 PM PST
The eneloop triple-A cells are rated 800mAh (actually tested to be 827mAh when freshly charged). The double-A cells are rated 2000mAh and tested exactly that.

Posted on Feb 17, 2007 4:04:25 PM PST
[Deleted by the author on Feb 17, 2007 4:06:51 PM PST]

In reply to an earlier post on Feb 17, 2007 4:06:34 PM PST
M. Shin says:
Thank you for a detailed comment. It was very helpful.

I'm looking for AA NiMH rechargeable batteries & charger for my external flashlight (580EX for Canon Rebel XT). After using this for 3 months, I finally realized that I'd be better off with rechargeable batteries.

I tried to look for unbiased reviews or technical articles to help me buy the "best" rechargeable batteries for my situation, but I've been unsuccesful so far. The only thing that I have learned is that I should look for 2500~2700mAh batteries.

Also, it seems like many ppl have a good experience with LaCrosse BC-900 charger, including yourself.

I was just wondering if you can share what rechargeable batteries you use yourself or point me to any informative websites on this topic. TIA.

P.S. What happens to these NiMH batteries if they are left unused for a long time?
For example, would they still work (well) if I opened them up after leaving them in the drawer for 5 years and then try to charge them and use them? Thx again.

In reply to an earlier post on Feb 19, 2007 8:09:08 PM PST
Last edited by the author on Feb 19, 2007 8:27:44 PM PST
I have the Canon 420EX flash. I'll choose the 2000mAh eneloop cells over ordinary NiMH cells any time, even if the the latter is rated for 2700mAh(*). My flash sometimes sits in camera pack for weeks. With ordinary NiMH cells, since the self discharge rate is around 30% per month, I must remember to recharge the cells before any major photo event. With the eneloop cells, I don't have to worry about it. But of course, I still keep a set of four alkaline cells in my camera pack just in case.
(*) Based on energy stored in a photoflash capacity (assuming 250uF charged to 320V), I estimate a set of four 2000mAh eneloop cells can provide around two thousand full-blast flashes. I don't think it is possible to shoot that many flash photos in any photo event.

The LaCrosse BC-900 is the best NiMH charger I know. The capability to actually test and see the capacity of each cell is worth paying extra for the charger. Sometimes in a set of four batteries, I'll find one that has much lower capacity, and that drags down the capacity of the whole set. With the LaCrosse I can match up cells with similar capacities.

The old NiCd cells usually go dead (develop internal short) if left unused for a few years. I'm not sure if NiMH cells have similar problems. What is the point of buying rechargeable batteries and then leave them unused for 5 years, anyway?

In reply to an earlier post on Feb 20, 2007 11:01:28 AM PST
M. Shin says:
Awesome, thx for the quick reply. I really appreciate it.

The question on not using it for X number of years was just a hypothetical question. Was just curious. Thx again and I'll be ordering those Eneloops.

In reply to an earlier post on Feb 20, 2007 2:37:56 PM PST
Last edited by the author on Feb 20, 2007 2:38:37 PM PST
swingy says:
"
(*) Based on energy stored in a photoflash capacity (assuming 250uF charged to 320V), I estimate a set of four 2000mAh eneloop cells can provide around two thousand full-blast flashes. I don't think it is possible to shoot that many flash photos in any photo event."

I don't know about this - I am a pro photographer and it takes far far less flashes than this for the batteries to run down. So maybe in theory... Also it takes far longer between flashes for the flash to reach full capacity as the batteries are used.

These are great for situations where you will need the batteries long times, like flashlights, clocks, remotes and other uses. They are not as good for situations where you need lots of capacity ready. A 2700mah would be better in those cases with 35% more capacity (for example, a long photoshoot) and where you can come back later and charge them.

In reply to an earlier post on Feb 20, 2007 2:56:29 PM PST
Last edited by the author on Feb 20, 2007 3:19:02 PM PST
Here is how I arrived at the estimate for number of flashes:

Energy stored in a capacitor E = 0.5* C * V * V
Let C=250uF (0.000250F) and V=320, we get E=12.8J
Assume efficiency of photoflash converter to be 70%, input energy required is 12.8/0.7 = 18.3J
Total energy stored in four eneloop cells (2Ah, 1.25V each) is 1.25 *4 * 2 * 3600 = 36000J
Divide 36000 by 18.3 and we get 1967, which is the total number of flashes possible.

In reply to an earlier post on Feb 28, 2007 11:59:24 PM PST
J. L. says:
NLee, you seem pretty knowledgeable, so here is a question.

I also have the eneloops (in both AA and AAA), however, fully charged they are at 1.47v. How come in a couple of days they drop back down to 1.39v? Does that indicate a faulty LSD battery? or is this normal?

Also, let's suppose the eneloops were fully charged a week before. Then I put them in the BC900 to charge them. Does the [mAh accumated before it's fully charged] = the mAh lost in self discharge?
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