Eneloop Panasonic BK-4MCCA4BA AAA 2100 Cycle Ni-MH Pre-Charged Rechargeable Batteries, 4-Battery Pack

Eneloops have been my go to for a while now. Out of all of the brands that I have used over the last 30 years these have lasted the longest. I prefer the standard eneloop because while the pros charge faster they also wear out faster as well. With the standards they last considerably longer but they take an hour longer to charge. Well worth the extra life I think. I use these for everything and they constantly deliver. They last so long that I have some that are over a decade old with 93% of their total life left. You can't go wrong.

As non lithium rechargeable batteries go, these are just the best. I've been using them for maybe 10 years, charged in countless cycles and i haven't really noticed any degradation yet. Sometimes the voltage isn't quite as stable as an Alkaline (or lithium) battery, but they do a terrific job relative to the Ni-Cd batteries i'm used to thinking of when i think of rechargeable batteries. Frankly, so many budget Alkaline batteries are terrible out of the box, anybody used to buying cheap AAA or AAs would do so much better with these. If you're not comparing them to the modern Energizer Max batteries, you won't notice a voltage sag. I expect I'll be using these same batteries for quite some time.

[this review is for the AAA 8 pack, although much of the information applies to other Eneloops.]The batteries arrived packaged on a card as shown in the photo on this page. I confirmed these are the latest 4th generation Eneloop batteries as advertised. The date of manufacture is imprinted on every battery, and although difficult to see, I found this set was made 5 months prior to receipt.With any low self discharge battery (LSD NiMH), one should perform an initial and periodic "conditioning" comprised of charging and discharging the cell 3-5 times in a charger that has this function (sometimes called "refresh") in order for the cells reach their maximum energy storage capacity. After conditioning the AAA batteries, all 8 exceeded 750mAh capacity (the advertised minimum), with values ranging from 762mAh to 778mAh. The very narrow range is an indicator of high quality and consistency in the manufacturing process.What follows are general recommendations to get the most from Eneloop and other LSD NiMH rechargeables....Get a good quality charger if you use Eneloops or other LSD NiMH batteries. Cheap chargers will significantly shorten the life of these high quality and somewhat expensive rechargeable batteries. The charger must be a microprocessor controlled "smart" charger that chargers each battery individually, not in pairs. I use a Titanium "smart fast" charger when bulk charging many batteries, and a Opus BT-C2000 when trying to get accurate measurements on capacity and internal resistance. These are there several others good quality chargers out there so be sure to read reviews from people who understand and discuss the technical aspects of battery chargers. That 15 year old old battery charger you have that came packaged along with some long since thrown away rechargeable batteries should not be used.Not all devices are designed to work with rechargeable batteries. The nominal voltage of rechargable NiMH batteries, 1.2 volts, is less than the alkaline equivalent at 1.5 volts. Some devices work well with either one and some are only designed for the higher voltage alkaline. This not a problem with the battery, it is a problem with the way the device is designed. Unfortunately it's rare for a device manufacturer to mention how (or if) it works with rechargeable batteries so you will have to test it or read the experiences of others.Devices that display the amount of power left in a battery will be inaccurate when using rechargeables and tend to indicate the batteries have less power than they really do. A device may show 2 out of 4 bars, when in fact the Eneloop might really be at 85% of charge.Rechargeable batteries like Eneloops (LSD NiMH), store 20-35% less energy than a good quality alkaline of the same size. This is not a "problem" with the rechargeable battery, it is a characteristic of the chemistry and how the energy is stored. That means you can not expect them to last as long between charges as an alkaline before replacement in most applications. LSD NiMH batteries however do hold more energy and last longer than carbon zinc batteries aka "heavy duty" (these are the really cheap batteries you may see at the dollar store or come prepackaged with low end flashlights).Rechargeable batteries should not be *over* discharged as it will damage them. Unfortunately it's hard to tell exactly when the ideal time is to recharge so it's better to stay on the safe side and recharge early when device performance starts degrading and not wait until it's completely dead. The best way to tell for certain is to test with a battery tester that measures voltage under load and recharge when the battery gets to about 1.1 volts Even some cheap battery testers can do this (look for BT-168D) or for a more expensive one the ZTS mini 9R. If all you have is a voltmeter, recharge when the open circuit voltage at rest is about 1.22v.Rechargeable batteries should not be charged too quickly as the internal heat build up will damage them. For AAA NiMH, it should take 2-5 hours to charge fully depleted batteries. If your charger goes from empty to full in 30 minutes, it is either damaging or under charging the batteries.Devices that automatically charge the batteries, such as cordless phones or cheap solar lights, are not a good candidate for Eneloops. These devices use "dumb" charging circuits and will likely overcharge the batteries shortening their life. For these types of batteries you are better off with cheap NiMH batteries that are not marketed as low self discharge (LSD).Devices that use a very small amount of constant power, such as a battery powered clock, might be better off with an alkaline. An alkaline may only need to be replaced every 3 years in such applications, where as the rechargeable may need charging in less than a year due to higher self discharge rate and lower nominal voltage. You will need to test it to be sure and decide what makes the most sense.Infrequently used low power devices such as a TV remote in a spare bedroom are usually better off with alkalines. A high quality alkaline may last 5 or more years, and the cost/benefit of an LSD NiMH just isn't there. Be cautious of low quality batteries this these sorts of applications as the battery may leak after a couple of years.Eneloops (and LSD NiMH in general) are better than alkalines in high current applications. An Eneloop can move energy faster to the device than an alkaline. Examples where LSD NiMh out perform alkalines are modern photographic flashes, remote controlled cars/planes, certain high output flashlights.Marking your batteries is a good idea, especially with you have many purchased at different times that all look the same. I mark mine by putting the year/month I purchased them, followed by a unique letter. When I first get them, I test their capacity and log it for future comparison. Even if you don't have the equipment to perform extensive testing, just knowing when you purchased each battery can be helpful down the road.Properly managed, high quality LSD NiMH batteries like Eneloops will give a long life. Abused, they will not do any better than cheap NiMH batteries. Most of the complaints and bad reviews are from people who do not understand the limitations, use them in the wrong application, or who do not properly charge them. Correctly using rechargeable batteries takes some work and isn't for everyone, but if you can deal with their idiosyncrasies, they can save a lot of money in the long run.

I bought these 5 years ago in 2020 and they still work well in 2025.I don't think I need to recharge them any more often than I used to buy new batteries and recharging is way easier so they've been a good purchase.

good stuff. I 've recharged probably 3 or 4 times so fa so they've pretty much paid for themselves. IF I get say 20 recharges, a bargain.

If you already have the charger, this is the way to go. You will save both the planet and Money. these hold a charge for years in storage and work as long as the name brands when in use. They charge failry fast. Great buy!

When I buy a new battery operated product, I throw away the batteries than come in the box, and replace them with these, because these don't leak and ruin the product.

I absolutely love the Eneloop Panasonic AAA rechargeable batteries! They have truly transformed how I power my devices - delivering reliability, longevity, and sustainability. With a remarkable 2100 cycle lifespan, these batteries not only save me money but also reduce waste. I highly recommend them to anyone seeking an eco-conscious power solution.