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575 of 593 people found the following review helpful.
Shockingly high self-discharge rate!
By NLee the Engineer
All rechargeable battery makers love to brag when it comes to their product’s current capacity (mAh). But there is a dirty little mystery that they don’t want you to hear: self-discharge rate. Simply put: a completely charged NiCd or NiMH cell will gradually lose it is stored energy over time. Technical papers I have researched distinctively put the self-discharge rate at 10-20% per month for NiCd cells, and 20-30% per month for NiMH cells. This kind of self-discharge rate is normally satisfactory in apps such as digital cameras.
I purchased 8 of those Energizer 2500mAh rechargeable NiMH batteries over one year ago. At first, I was very happy in regards to the huge current capacity offered by those batteries. But within a few months, I started to observe that they die very speedily in my digital camera. In fact, a set of Sony 2300mAh NiMH batteries I purchased one year earlier seems to last much longer when employed in the same camera.
I not long back did some controlled experiments (using the LaCrosse BC-900 AlphaPower Battery Charger) and found out what’s wrong: The Energizer NiMH batteries have very high self-discharge rate. After completely charging all 8 cells and left them on the shelf for one week, five of them lost over 30% of their charge, and the other three lost in regards to 20%. In comparison, the set of older Sony batteries only lost around 10% over the same one-week period.
So what this genuinely means is: if I charge up those Energizer 2500mAh batteries and leave them in my camera for three weeks, they will become altogether exhausted. I found this kind of self-discharge rate wholly unacceptable, hence I strongly advise versus buying those batteries.
[Update on April 9, 2007]
I have hardly used those Energizer 2500mAh cells in the last few month. Now they have deteriorated even further. Five of them can’t even hold their charges for more then a day.
Instead of the Energizer 2500mAh cells, I commend buying the Rayovac “Hybrid” 2100mAh cells. They have very low self-discharge rate (see my review on “RAYO 4PK AA”) and are for less than the better-known Sanyo eneloop 2000mAh cells. Kodak likewise sells a “Pre-Charged” NiMH cell with incisively the same spec as the Rayovac Hybrid.
The bottom line: Low-Self-Discharge NiMH cells are your best choices. There is utterly no point in taking probabilities with older generation 2500-2700mAh NiMH cells now.
[Update on Oct 20, 2010]
The product effigy of Energizer Rechargeable AA has changed. It no longer advertises ’2500mAh’. I went to my local W*mart to check out the actual batteries. All Energizer rechargable AA cells are now 2300mAh. Evidentially, Energizer has ‘rollled back’ battery technology to 2004. This is in truth a good move because the lower capacity cells do not suffer from hideous self-discharge rate. Contrary to ordinary belief, a 2300mAh cell is not any less competent in delivering high power than a 2500mAh cell. Just that the run time will be regarding 8% shorter.
36 of 37 humans found the following review helpful.
Unreliable Energizer 2500 mAH AA experience
By W. Munn
I’ve been using NIMH batteries from SANYO, NEXCELL, POWEREX and AccuPower for over 6 years. Use them for everything from high current drain digital cameras and high-end digital audio recorders to CD players, bathroom scales and flashlights.
I rely on two of the splendid MAHA MH-C401FSB smart 2-rate chargers. These charge and monitor each battery independently, not in pairs. Energizer 2500 mAH units were fine for regarding three months. Then I noticed that gimmicks would be calling for new batteries with little to no use. This has never happened with other AAs NIMH, including those with less than half the advertised capacity. The MAHA charger also started reporting that a lot of of the Energizer AAs were not taking a charge at all.
Kept finding that specifically one out of four were the problem. Many of the 32 AA Energizers I purchased have had problems. Repeatedly have had one battery run out of charge while others still test very strong. Felt pen dots put on discharged batteries showed it was the same batteries time and time again. Have reverted in a lot of cases to 1600 mAH SANYO OEM batteries put in service in Feb 2001 and those provide longer and more authenti performance!
In my substantial experience with these 2500 mAH AA Energizers they have been a very big disappointment and, irrespective of warranty, can not be relied upon.
148 of 171 people found the following review helpful.
Shockingly good performance
By Sean Kelly
I purchased a bunch of Energizer’s AA ACCU NiMH rechargeable batteries to power a halogen bicycle light and LEGO Mindstorms robots. Their performance has exceeded my expectations.
The bicycle light seems as bright as it ever was with alkaline batteries, affording good visibility for the duration of night time cycling. And stopping play—er, experimentation—with the LEGO robots for recharging has yet to be a problem.
However, I do have to issue this warning: these batteries are somewhat fatter than popular AA batteries. I tried using them in a Mini Mag Light. After I got one battery in the light’s barrel, I realized—too late—that I’d never get the batteries back out. I ended up destructing the Mini Mag Light in order to retrieve the batteries.
If your application is cramped for space, beware! If they do fit, suppose good energy for a good long time.
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