What are Eneloop Batteries?

Frequently asked questions about Eneloop Batteries

(If you have questions about charging, check out our Eneloop Charging FAQ page)

Eneloop Versions and editions

What are Eneloop batteries?

Eneloop batteries are rechargeable NiMH batteries. They are famous for their extremely Low Self Discharge characteristics. This means that they can keep a charge longer than any other NiMH or NiCD rechargeable battery in the world. Besides this, they can also produce a lot of power, more than their competitors can do.

What’s the difference between Sanyo Eneloop and Panasonic Eneloop batteries?

Sanyo started as the manufacturer of Eneloop batteries in 2005. Panasonic bought Sanyo 5 years later, and in 2013 Panasonic decided to change Sanyo Eneloop to Panasonic Eneloop.

Eneloop Vs Eneloop PRO Vs Lite, What model do I need?

Standard:
These are the most popular.
Because the standard white model can be used in almost any kind of application. They are robust enough to handle a very high discharge current for example in powerful flashlights and RC cars. In combination with their life cycle rating of 2100, you can’t go wrong with the standard models in almost all cases. They power 1900mAh minimum capacity for their AA and 750mAh for their AAA batteries.
They are good for Flashlights, RC Toys, Cameras, Camera Flash, Radios, MP3 players and much more. See more details on the Eneloop tests page.

Lite:
These cells are rated for 3000 cycles (for the Japanese model) or 5000 cycles (for the Chinese model) but have a much lower capacity at 950 mAh for the AA and 550 for the AAA. Besides using them in low drain devices such as clocks, alarms, remote controls, and such, these are the only batteries really recommended for DECT phones. (even though the standard Eneloops are sometimes recommended as well, Lite cells make much more sense). Standard and Pro batteries are not recommended for this. Because the phones usually stand in a charging cradle with a continuous trickle charge. LSD batteries do generally not like that, but the Lites are the only ones to consider for that kind of use.

Pro:
It’s called the High-End battery in their line-up. Featuring the highest capacity with an LSD rating of 85% in 1 year. Being a high capacity cell, they are only rated for 500 cycles.
If you need the extra power and the extra capacity these are the ones to get. Especially in multiple cell configurations. If you have 4 batteries parallel you gain the capacity of 1 extra std cell in comparison with 4 std cells parallel.
These are highly recommended for Flashlights, Camera strobes, and other powerful devices.
These are NOT recommended for DECT phones or other devices with a continuous charge current.
Another thing you have to consider when buying these Pro batteries is the fact that they are just a tiny bit wider than the standard ones which may result in not fitting. This is such a tiny bit of difference that most people do not notice it. Sanyo noted that they do not fit the AA to D size spacers (NCS-TG-D). They may have changed this with their latest Panasonic upgrade (BQ-BS1E). Be careful, these battery jackets are easier to damage! Read more on the dedicated Eneloop PRO page.

Are there any Eneloop C or D cells?

Yes, there are. But they are only available in Japan. You can however buy AA to D and AA to C spacers that will allow you to use AA batteries in D-sized applications. The disadvantage is less capacity.
Additional:
The current C and D size Eneloops have sets AAA and AA batteries internally.
In the international non-rechargeable battery market, AAs and AAAs have about 95% of the overall volume and 5% for C or D sized cells. In the NiMH market, AA and AAA’s share about 98% of sold batteries. So there isn’t enough of a benefit from making an investment into new machinery for such a minor part of the market. *1

70% capacity left after 10 years. What does that mean?

Please take a look at the picture:
As you can see some packages say 70% charge left after 10 years, and some packages say 70% capacity left after 10 years. This can be confusing. They basically try to say the same thing.
Comparing this with a bucket of water:
An AA standard Eneloop battery has a capacity of 1900mAh. (Let’s compare this with a 10-liter bucket of water).
After 10 years the Eneloop battery slowly loses its charge. (The water evaporates from the bucket).
There is still 70% charge left inside the battery after 10 years, which is 70% of 1900= 1330mAh. (after 10 years there is still 7 liters of water inside the bucket because 30% has evaporated).
You can still use 1330mAh from this battery. (You can still use the 7 liters of water).
When you charge the battery fully again it is back at 1900mAh. (When you fill the bucket of water it can hold 10 liters again)
Misconception:
10 years after you fully charged the battery and left it untouched, the battery life degraded to 70% of its full potential. So even if you charge the battery, you can only charge it till 70% of its full capacity. This is not true. If you charge the battery again, it can come back to full capacity. So in the case of a standard AA Eneloop that means 1900mAh.
Note: The battery probably needs a refresh/break-in to revive the battery to its full capacity because of its internal resistance etc. Also, this is only related to Eneloop batteries. Other batteries don’t have this quality structure and are very likely to have degraded capacity.

What’s the difference between the 1900 mAh and the 2000 mAh Eneloop batteries?

Since 2022, there is a nuance.
Originally, Sanyo and Pansonic mentioned 2 capacity numbers, 1,900mAh as its Minimum capacity, and 2,000mAh typical capacity.
In Japan and Europe, Panasonic stopped showing its Typical capacity on their packages since, approximately, 2013. I believe the Typical capacity is still shown on some packages in the US.

But since 2022, there is actually a new standard Eneloop battery, the 5th generation. It increased the capacity from 1,900mAh to 2,000mAh. The new product code is BK-3MCDE (the letter D refers to a new, 5th generation, the last letter E refers to a region, Europe. Read more about codings here: https://eneloop101.com/batteries/how-to-read-the-code-and-manufacturing-date/

What’s the difference between the Chinese and Japanese Eneloop?

Original Question from the interview with the Eneloop engineer: What’s the difference between the ones that are made in China against the ones that are
made in Japan? Why doesn’t Panasonic produce the same quality in China as they do in
Japan?
The quality of the Chinese manufactured Eneloops has improved significantly since 2016. The main difference between them are the production machines. The machines used in Japan were the result of a very high investment to get the best possible machines. *1

Does Panasonic make 9V Eneloop rechargeable batteries?

Neither Sanyo nor Panasonic made or makes 9V Eneloop batteries. There is a 9V eneloop music booster though.

Are the blue Costco Eneloops the same as white Eneloops?

Yes, they are the same! Costco used to have its own color so to say, dark blue etc. Since 2018 they also have the normal white Eneloops. Their packages are also custom made for them, they are that big of a store!

I received Blue Eneloops from Amazon, are they real?

Yes, they are real and the same! From around March 2018, Amazon has been kind of flooded with blue Eneloops, usually

I found some orange, green, silver, grey and red colored Eneloops, are they real?

In certain stores and at Amazon.com, you can buy colored Eneloops. Like these green, orange, gray, silver, or red Eneloops. They are the same as the white standard models, 1900mAh for AA and 750mAh for AAA.
They are NOT a special edition as some sellers say they are. They are just designed for a specific store/seller/market.

*1= answer given by Eneloop Technicians during an interview when I visited the Panasonic office in Brussels

Eneloop Storage, Safety and Handling

Where should I store my batteries? And at what temperature? When used frequently

Your best bet would be storing them in a cool, dry place. Not in a humid, very hot, or wet environment. Sanyo recommended to store them around 24 degrees Celsius and not in a fridge/freezer. Panasonic says the same: do not store them in a refrigerator.

What is the best way to store your batteries for extremely long shelf-life (when not used in devices)

For absolute best shelf life, they are best kept in a cool environment, around 5-15 degrees Celsius. And at about 20-30% charge. The best is to first charge to 50% and then little discharge. Don’t charge up to 40% and stop, because somehow, the little discharge helps the battery to keep their charge for much longer. This is a well-known behavior, but even the experts don’t exactly know why this happens. *1

Is it safe to store Eneloop batteries for extended periods of time in a device?

If you want to store them for emergencies you could store them in flashlights and other emergency devices as long as the device won’t discharge the batteries by itself. A common problem with flashlights that have an electronic switch is their parasitic drain. In that case, I recommend to lock-out the flashlight so it won’t discharge the batteries.

How prone are Eneloops to internal cell damage because of physical shock and vibration?

For example, dropping them on a concrete floor from a defined height.
They aren’t easily damaged, so a drop from a meter wouldn’t be too troublesome. Added info through e-mail: The 1-meter drop test is also part of internal testing and should not be a problem in real-life conditions as long as the canister is not damaged. *1

Why you shouldn’t use Eneloops in airtight devices?

Original question: “Don’t use Eneloops in airtight devices?” some manuals say, what is the worst scenario that can happen related to this warning?
Answered by Belgium Panasonic employee: If they are severely discharged, they will vent a bit of gas due to the chemical reaction, and in the case of an airtight device, this could build up pressure.

Can I mix Eneloop batteries with the rest of the Alkaline batteries I have laying around?

No!
Don’t mix and match rechargeable batteries and Alkaline batteries, period. The most important thing to remember is to only use matching batteries in devices that use multiple batteries.
These batteries should have the same capacity, of the same brand, of the same model, with the same usage.

*1= answer given by Eneloop Technicians during an interview when I visited the Panasonic office in Brussels

Technical Eneloop questions

What’s the difference between an Alkaline or Zinc battery and Eneloop?

About Alkaline batteries:
pros:
They have a higher Voltage than Eneloops, being 1.5V. Sometimes this helps to power some devices that show Low-battery-warning with rechargeable NiMH batteries.
They have more energy at a very low current, <0.01A For example in clocks and remote controls
They are widely available almost everywhere in the world
You don’t need to buy a charger ;).
Cheap
cons:
They can leak. Especially when stored in devices for a longer period of time. Sometimes they leak even inside the original package.
They produce much more waste. Besides them ending in the normal garbage, many batteries can be found on the street and … adding to the environmental damage.
More expensive in comparison to recharging an Eneloop even just 20 times!
About Eneloop batteries:
pros:
Better in every other aspect.
They are rechargeable.
They can be used in colder weather.
They are much more powerful than Alkalines. Because of that, they are better for applications in which batteries need to provide more power.
Eneloops don’t leak as Alkalines do.
They have much nicer battery jackets.
They are collectible.
They are cheaper in the long run.
They reduce the amount of waste compared to Alkaline throw-away-batteries.
cons:
Price is higher.
Not widely available.

How do I read the manufacturing date on a Eneloop battery?

Please take a look at the explanation on our Eneloop codes and numbers.

Do Eneloops suffer from memory effect?

No, they don’t. They do not have a memory effect. But they do have a reduction in capacity over time. I think it’s called Lazy effect.. or something similar. It means that they will not have full capacity after many charges. With a “refresh” cycle you will be putting them back to their maximum capacity again. The maximum capacity depends on the amount of use, and age.

Technical difference between Eneloop and Eneloop PRO?

What are the technical/design/construction differences between regular Eneloops and Eneloop Pros, that allow the regular Eneloops to retain charge for longer and have more recharge cycles and the Pros to have a higher capacity?
More usable volume equates to more capacity. The Pro cells have thinner canisters and separators, allowing for more active material and electrolyte. The reason for a difference in cycle life is related to the ratio of positive and negative electrode material: the higher the ratio, the better the cycle life. With Eneloop Lite being on the opposite end of the Eneloop Pro, you can see the relation: https://main.panasonic-eneloop.eu/en/eneloop-self-discharge *1

How is the capacity of an Eneloop measured

That’s according the IEC61951-2 (2017) standards:

The rated capacity of a is the quantity of electricity (mAh) declared by the manufacturer which can deliver during a 5 h period when charging, storing and discharging under the conditions specified

Prior to charging, the cell shall be discharged in an ambient temperature of 20 °C ± 5 °C, at a constant current of 0,2 It A (0.2C) , down to a final voltage of 1,0 V.

The charging procedure for test purposes shall be carried out in an ambient temperature of 20 °C ± 5 °C, a relative humidity of 65 % ± 20 %, at a constant current of 0,1 It A (0.1C), for 16 h.
The tests shall be performed within 2 months of the manufacture date. Manufacture date is determined by the manufacturer.

The cell shall then be discharged in an ambient temperature of 20 °C ± 5 °C at at a constant current of 0,2 It (0.2C) in order to verify the declared rated capacity of the cell.
Minimum discharge duration will be 5 h.

Five cycles are permitted per cell for this test, and shall be terminated at the end of the first cycle of each cell which meets the requirement.
When conducting discharge performance testing all samples cells shall be tested to meet the requirements.

Why do PRO decrease in quality more quickly?

Original question: Why do Eneloop Pros decrease in quality so quickly? In real life, this can be seen with only 100 cycles of discharges or 2-3 years of use. Is it heightened internal resistance or another factor?
Yes, they do build up internal resistance over hundreds of cycles. And therefore can’t provide enough power output. The size of the positive electrode and negative electrode has to do with this. Positive has to do with Capacity, and the Negative has to do with Cycle life. The closer these numbers match, the shorter the lifespan. *1
Additional
Added info by Panasonic employee Brussels in an email: As mentioned before, the ratio between positive and negative electrode material will define the capacity. As an example, the Eneloop Lite has an equal ratio between both electrodes; in an Eneloop Pro, the ratio is skewed. That is due to the higher amount of positive electrode needed, which allows for higher energy density, but much more negative electrode material needs to be put to actually get more energy out of the cell. However, that lowered ratio leads to worse cycle life, and perhaps, heightened internal resistance.
Let’s just say the Eneloop Lite would be 1(capacity):1(capacity degradation); the Eneloop
Pro would be 2:4. These are not real numbers. Just examples.

What’s the relation between deep discharge vs cycle life and internal resistance

Original Question: What is the relation between deep discharging ( 0.9 Volt) versus cycle life and internal resistance? How deep of a discharge can occur before internal resistance rises? Can 1 very deep discharge permanently affect the cell? Reduced cycle life by X %? If Eneloop PRO is discharged below 0.6 of 0.9V would cycle life be reduced by 100 cycles?
The difference between discharging to 0.8V and 0.9V will only be a minimal difference in cycle life. And yes, the deeper the discharge, the higher the internal resistance rises over time. There is no real testing data to prove this point of how much % cycle life at a certain voltage is lost etc. but a deep discharge will reduce the cycle life, this can be by 1%, but
can be more as well. The most important factors are how long it stays fully discharged, and how deep that discharge is. *1

Is there a way to lower the internal resistance of an Eneloop when they age?

No, that is not physically possible. *1

Eneloops, and shorts, how do you know if it’s damaged?

Original question: Once a battery is inserted in a device the wrong way around, and shorts, and gets really hot, how do you know if it’s damaged?
With an alkaline cell, it is easy to see it leaking when damaged. With an Eneloop, it will also be a bad sign when the battery starts leaking, however, it is likely that it could still work. So the best way is to discharge it and see how much capacity is still available.*1
Additional info:
When you notice that the plastic battery wrapper shriveled up so it left the bare metal of the battery exposed, you have a shorted Eneloop. It is damaged beyond repair. You can toss it.

Could you apply the Eneloop technology to NiZn batteries? (nickle zinc)

No, they use totally different ingredients and are very unstable.*1

*1= answer given by Eneloop Technicians during an interview when I visited the Panasonic office in Brussels

Eneloop Fun Facts

Are Eneloop batteries the best?

Quite frankly, in almost every battery comparison test Eneloops are at the top. Not always #1, because some other high capacity cells like the Panasonic 2700 do a very good job as well in high drain devices. But have a look at the many tests in the Eneloop Test section on this website.

The only place they don’t excel is in extreme low drain devices, like clocks. But that is for NiMH batteries normal, and Alkaleaks (Alkaline) have always an advantage here.
Also keep in mind, that rechargeable batteries are usually used more than once, and therefore it is important to look at the lifespan of the batteries as well. Many reviews on the internet forget about that. Like the wirecutter reviews as a prime example.

What does Eneloop mean?

Sanyo decided in 2005 to name their new batteries eneloop. ene = energy, loop= cycle. Meaning that energy can be recycled. Or to put it in their own words “rechargeable energy”.

Why did Eneloop use the crown symbol on the first Eneloops?

It was one the designer’s idea, but it came from the idea that the Eneloop is the king of batteries. *1

What does the orange symbol mean on a Japanese Panasonic battery?

Japan uses 4 different symbols for its battery recycling system. NiMH has an orange recycle symbol. Take a look at the following list. You might have seen the blue Li-Ion recycle symbol on your laptop battery for example. Japan has a very good organized recycle system with lots of variations.

What are the rarest Eneloops?

That must be the Eneloop Plus. They were only available in 2 or 4 packs, and in charger sets.
Besides these cells, the older Sanyo Limited Editions are becoming more difficult to get, at a normal price. They tend to go for $50+ for a set of 8 batteries. D and C cells are also only available in Japan.

Why are new Eneloop models in Japan usually introduced in the month of November?

This is my understanding of how much I understand it : -)
Reason 1:
Because Eneloop was first announced in November 2005, so November would be an anniversary month. But I think it has to do with the 2nd reason as well.
Reason 2:
November is called the battery month in Japan. This “battery month” was first established in 1997. It has to do with how you write the number 11 in Japanese. It is written as 十一　and you can guess what those symbols stand for. And that might be the reason why Eneloop was first announced in November anyhow.
So how about April then?
April is the first month of the financial year as well as the academic year in Japan. That might be the reason that they sometimes introduced new batteries in April?

What does LSD stand for (regarding batteries)?

LSD stands for Low Self Discharge.
Every battery that is stored away (or not being used in a device without a parasitic drain) loses its charge. This is referred to as Self Discharge. Eneloop batteries use high-quality materials and an improved manufacturing design that will decrease this rate of discharge to a minimum. The result is that they lose their charge much slower than a traditional NiMH battery.

What will the New Eneloop look like?

Original question: What new research is being done on making better batteries? What will the next generation be like? Will the new AA standard (same quality) ever be more than 1900mAh?
There isn’t anything new on the horizon, but they are currently trying to find a way to minimize the drop from 100% to 90%. The fastest discharge happens between a fully charged battery and about 90%. They would like to figure out to get rid of this quick drop, and have even better LSD capabilities.*1

What are the best rechargeable batteries?

Eneloops! Not kidding. You can’t go wrong with Eneloops in any category. Be it low-drain, high drain. Eneloop batteries are always at the top of every test. Especially considering long-term use! Also, check out all the tests to see why they are the best rechargeable batteries.

*1= answer given by Eneloop Technicians during interview

How to charge eneloop batteries

Charging batteries can be as simple as inserting the batteries into a battery charger. But there is more to it. Read all details in our Eneloop Charging guide

Eneloop Charge guide

Where can I buy authentic Japanese Eneloops?

I decided to dedicate 1 page to places you can buy Eneloops. I highly recommend that you verify that the source is legitimate. Since 2017, there are many fake eneloop PRO batteries on the market, and especially on eBay.
It depends on where you live. But, if you are in the EU or US there are tons of places to get authentic Eneloops. Amazon, Bestbuy, Conrad. If you are from Asia, South America, Africa, New Zealand or Australia it is more difficult, because you mainly have Chinese Eneloops in your stores. You would need to buy them overseas.