Customer Reviews

Energizer Rechargeable AA NiMH Batteries, 8-Count

5 star:		(30)
4 star:		(12)
3 star:		(3)
2 star:		(12)
1 star:		(33)

 

 

All rechargeable battery manufacturers love to boast about their product's current capacity (mAh). But there is a dirty little secret that they don't want you to hear: self-discharge rate. Simply put: a fully charged NiCd or NiMH cell will gradually lose its stored energy over time. Technical papers I have researched typically 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 usually acceptable in applications such as digital cameras.

I bought 8 of those Energizer 2500mAh rechargeable NiMH batteries over one year ago. At first, I was very happy about the large current capacity offered by those batteries. But within a few months, I started to notice that they die very quickly in my digital camera. In fact, a set of Sony 2300mAh NiMH batteries I bought one year earlier seems to last much longer when used in the same camera.

I recently 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 fully 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 about 20%. In comparison, the set of older Sony batteries only lost around 10% over the same one-week period.

So what this really means is: if I charge up those Energizer 2500mAh batteries and leave them in my camera for three weeks, they will become totally exhausted. I found this kind of self-discharge rate completely unacceptable, therefore I strongly advise against 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 recommend buying the Rayovac "Hybrid" 2100mAh cells. They have very low self-discharge rate (see my review on "RAYO 4PK AA") and are cheaper than the better-known Sanyo eneloop 2000mAh cells.

[Update on Oct 20, 2010]
The product image 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 actually a good move because the lower capacity cells do not suffer from hideous self-discharge rate. Contrary to popular belief, a 2300mAh cell is not any less capable in delivering high power than a 2500mAh cell. Just that the run time will be about 8% shorter.

I gave these cells lowest possible rating because sharp decline in performance after only a few months of usage in a digital camera is not acceptable (especially considering claims on the package that these cells are GREAT for... digital cameras!). But also because much better alternatives have come on the market (e.g. Sanyo's Eneloop cells) and there simply is no reason any more to buy the Energizer 2500mAh as they have become obsolete.

I have experience using these cells for the past 2 years in 3 distinct and very different usage patterns:

1. My sister used 2 pairs in a digital camera
2. My mother used 3 pairs in a wireless mouse and keyboard
3. I used 6 pairs in various baby toys (non-motorized baby toys that play sounds and flash lights) as well as in Bluetooth keyboard/mouse and back-light IR remote control.

Because each set was never mixed with other batteries (they 'lived' in different households) - I can draw some conclusions on how these batteries hold up under varied usage conditions (by which I mean - various discharge profiles from the most intense - in digital camera - to the least intense - in IR remote controls and baby toys). Also - it's worth noting that all 3 sets of batteries were charged with identical chargers - the Maha MH-C401FS and they were ALWAYS charged on 'slow' or 'gentle' setting (around 5 hours per charge; I made sure my sister and mother understood very well to never EVER use the 'fast' 100 minute setting as it's detrimental to battery life). By the way: none of the sets got anywhere near the 1000 re-charge cycle touted on the packaging.

So what are the results of the 3 tests?

My sister, who put the most strain on her batteries in a high-drain digital camera, essentially killed her 2 sets. She still uses them - but they hardly hold charge any more.

My mother's cells still work - but they only hold sufficient charge to power her keyboard/mouse combo for about a week before they have to be recharged. Wireless keyboard / mouse is a rather low drain device though they do not have a 'sleep' function (pls see below for how this compares to a Bluetooth version).

My batteries - under the least strenuous usage of all 3 sets - held up the best. They still hold charge long enough to power any of my devices for 30 days or better. IR remote only actually drains batteries when you push buttons. Baby toys I use these cells in don't have any motors - and just like the remote control - only drain the cells when the kid presses buttons. Drain is fairly low (most of the toys simply play sounds; some also flash LED lights; none have moving parts). The Bluetooh keyboard and mouse are also low drain and unlike their 'standard' cordless brethren - they go into 'power save' or 'sleep' mode when not used for a number of minutes. This saves tremendously on power usage.

Given my experiences - the bottom line seems to be that these are OK as long as you don't plan on using them in a... digital camera. Just like other reviewers have noted - these cells are excellent in any kind of device when brand new. But after a few months of running them through their paces - they seem to kick the self discharge rate into overdrive. I hardly experienced this self discharge acceleration (though all of my cells did lose about 300mAh of capacity under my usage over the past 2 years; as tested by my newly acquired LaCrosse BC-900 charger). But both my sister and my mother definitely noticed a sharp deterioration.

However, all of this discussion is of little more than historical value at this point. 2 years ago - there were not that many other options for high capacity Ni-MH cells and these Energizer 2500mAh batteries seemed like a good idea. These days - Eneloop cells are available from Sanyo and other 'low self discharge' Ni-MH batteries are also available (often advertised as 'pre-charged' batteries; Wal Mart sells a product called Rayovac Hybrid for less than these Energizer cells; even RadioShack has a house brand; though at ridiculously high price and made in China). So I no longer see a reason to buy the Energizer 2500mAh cells - especially given that Japan-made Eneloop cells from Sanyo are only slightly more expensive. I'm in the process of replacing all of our batteries with Eneloops. Stay tuned for Eneloop review in... 2 years ;-)

I have three cordless Uniden phones that all have serious battery charge problems wit the original 1500 Mah batteries. I bought these (2300) and charged overnight. They work great and are the best battery out there for AA nimh required devices. Don't buy no-name garbage to save 10%, not worth damaging your electronics over it.

I bought these AA batteries a while back and it is still working well. I bought some cheap ones before to save a buck or two, but didn't last that long. It was a waste of money. I use these batteries mostly for my Nikon coolpix camera. Just charge over night and it'll be ready the next morning.

I have bought two sets of Energizer NIMH AA batteries and had them for

about 1 year. As others have reported they seem to work fine for

about 2 to 3 months and then they self discharge rate makes the

batteries almost unusable. After fully charging the batteries

and trying to use them one week later my digital camera will

tell me to change the battery pack without even using them.

I bought 20 of these on the recommendation of others. THey worked great for about 4 months, and then they stopped holding a charge. I can charge them up and leave them in my camera for a few days and it will tell me they are dead.

Energizer NiMH are no good; go with Sanyos instead, you won't be disappointed.

I use these batteries with the Energizer Quick (15-min) charger. It's important to note that these are the 2500 mAH batteries. Energizer also makes 2100 and 2200 versions that are sometimes erroneously listed as 2500 on others' websites. These are the real deal.

They charge within 15 minutes in the charger and keep their charge as indicated. I keep extras with me when I am photographing, as my flash is power hungry. I often get more flashes out than the manufacturer claims is possible with its own proprietary battery.

I have charged, discharged, and recharged them many times with no noticeable loss. They do get very hot in the charger and need to cool before using. Also--and this is probably obvious--they do not work once wet, even if allowed to dry. (I had an unfortunate experience with a canoe and a lake.)

These batteries are do a great job of providing long life in high curent drain applicaions. I recently bought my wife an iGolf GPS unit that measures the distance to the middle of the green using GPS technology. The unit works great but only lasts ~ 10 hours on a set of alkaline AA batteries. After looking into some alternatives I found that these Energizer AA NiMH batteries have the highest capacity (mAh) of the brand name batteries available. The result is that after a full charge she can get upwards of 12-14 hours of iGolf usage before the batteries run out. You can access the technical specification sheets on the enegizer web site and detemine if they would work well in your particular application. I suspect that some of the other reviewers which are having problems may be using them in devices where 1.2V (NiMH chemistry) do not work well and require a conventional battery (zinc carbon or alkaline) that delivers a full 1.5V. If your application can use the slightly lower voltages that these deliver then they are a great buy and should save you some money in the long run.

Recharge 1000 times? We have recharged these batteries 50 times at most and then they start to fall of real fast. I was surprised because I really believed they were the best way to go.

Great in digital camera. Took 400 photos on trip to Mexico.

Way out-last conventional for short intense power needs.

They do lose power just setting around over a month's time. Make sure they are freshly charged before extended use.