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Do ‘ultra-high’ capacity batteries really exist?

The higher a rechargeable battery’s capacity, the longer it should last per charge. But are ‘ultra-high’ capacity batteries really worth hunting down? And do you bother looking at the capacity anyway?

Before I got involved in battery testing at Which? I had no idea what to look out for when choosing rechargeable batteries. I’d probably have chosen the cheapest I could find from a brand I’d heard of.

Now, having just written my third battery article for the magazine, I am a little wiser in the world of batteries, and know that if you don’t have our Best Buy battery information to hand, then looking at the stated capacity (‘mAh’ number) on rechargeable batteries is your best bet for predicting how long they’ll last per charge.

But I also know from our lab test results that you don’t always get quite what you’re expecting…

‘Ultra-high’ capacity batteries

In our latest batch of rechargeable batteries, we tested the highest capacity AA rechargeable batteries I’ve seen – the Ansmann Digital 2850mAh. Our test lab suggested them and we had high hopes that these batteries could smash battery lifetime records.

But it wasn’t to be. While these batteries certainly didn’t do badly overall (see our full rechargeable battery test results for details) we didn’t achieve anywhere near the 2850mAh we were hoping for.

When we charged them up in our generic smart charger – representing everyday use – they only achieved 2225mAh on average. This is just 78% of their claimed capacity and is lower than some of the other batteries on test.

Do you look at battery capacity?

Ansmann told us that its batteries achieved 2,723mAh when they tested them according to the EU Directive and claims that under its ‘normal’ conditions they have achieved over 2800mAh.

But this got me thinking – are these ultra-high capacities achievable in real-life situations? Plus, how many people look at claimed capacities when choosing rechargeable batteries anyway?

We recently noticed that Asda, Sainsbury’s and Waitrose weren’t displaying the capacity information when selling batteries online – and have asked them to sort this out. But even when they do, is this the type of info you’ll look out for when battery shopping?


I use disposable batteries mainly for low consumption items such as clocks, remote controls and infrequently used torches, where batteries will last a year or more. Capacity is not very important to me and I tend to buy known brands that are on offer at discount prices. I do check expiry dates, but these are now so long in the future it is less of an issue than it used to be.

I have always been impressed by the capacity of Duracell batteries but have had many leak over the years, usually when they are nearly exhausted. As I write, I’m looking at a couple of used Duracell Plus batteries dated Mar 2014. Both have leaked at both ends and could have caused damage if they had been in an appliance. I don’t recall Which? testing batteries for leakage.

I use rechargeable batteries or equipment with rechargeable batteries for most purposes and have few problems.

Use LED lights for illumination purposes that cost virtually nothing to run
…. use super/alkaline batteries bought from 99p shop for other functions
that can have life extended on a recharge using battery charger OR by
heat treatment (other method demonstrated on YouTube I’m
not keen on).

Dearer rechargeables are not that very good and I no longer use
them in particular as to both AAs and AAAs.

To clarify things a little, YT demo was a third option.

Now that cameras and other portable appliances come with rechargeable batteries I make far less use of rechargeables than I did a few years ago.

Ultra-high capacity is not important for me at present, but may be relevant in the future. What I value is rechargeables that retain their charge for an extended period and I would be interested to know if those that keep their charge well continue to do so when they have been recharged a few times. It is maddening to have sets of recharged batteries ready for use, only to find that they have lost their charge.

Thanks Hazel. I might invest in some new rechargeables. I have plenty that work fine but probably nothing less than five years old. I’ll go back to the report and check the recommendations for ones that hold their charge best.

David Lowe says:
18 April 2012

I have tried many rechargeable batteries over the years to avoid the high cost of one-shot batteries.
This really became important when used with my cameras that used 4 AA batteries. But your review does NOT mention what I consider to be a MAJOR point is that rechargeable s are only 1.2V whereas regular dry cells are 1.5V : Many devices perceive these 1.2V rechargeable s to be partially depleted and therefore the batteries have a very short useful function. With my Fugi camera I had to carry around 8 spare rech. batteries to ensure a full days use of the camera.

Using rechargeables will mean that the battery capacity indicator is not accurate because it is designed for the higher voltage of disposable batteries. The rechargeables may last longer but the battery indicator will not be much help in warning when they run out.

Well designed equipment will otherwise work just as well with rechargeables as with disposable batteries, but some equipment is poorly designed.

William says:
26 April 2015

Why can’t they make them 1.5V instead of 1.2V?

It’s a limitation of the chemical process. NiMH are 1.2V, Alkaline are 1.5V and Lithium are 3.7V, PER CELL. Cell meaning in this case, the lowest divisible component. These voltages are the natural output of the battery, using the chemical processes that they use to generate power. Recently, we’re starting to see innovations such as Lithium-ion batteries produced that include electronic circuitry which reduces the Voltage, so that they output the common 1.5V standard of Alkaline battery output. These are obviously more costly and also have the disadvantage that the space used by the added circuitry is lost for the chemical components, that store the charge. The pros and cons of the different cell chemistries are discussed elsewhere.

You can buy aa 1250 mah znter 1.5 rechargeable batteries on e bay for £15 for 4 batteries.
Charge by usb cable only

anon the mouse says:
18 April 2012

The tech geek returns 🙂

Extended phone batteries are definitely worth the money. Okay so a 2800mah might only give you 2400 or even 2200, but when the battery that comes with your phone is only a 1400, it makes a world of difference. Okay the phone gets a bit bulkier, but it’s definitely a decent trade off.

My Optimus 3D went from being able to see the battery level dropping (2 hours heavy usage max) to being able to get through 2 days of that same heavy usage. My brothers Galaxy S2 now gets 3 days use rather than almost 1.

If phones are doing more and more, why are the batteries getting smaller and smaller capacities?

If you’d like to see the difference in batteris goto Amazon and type in “your phone” extended battery

Hazel’s Conversation is about standard rechargeables such as the common AA size, and not the specialist lithium rechargeables which come in many sizes and are used in phones and most cameras. I completely agree about the inadequate capacity of phone batteries.

Steve Price says:
20 April 2012

Like wavechange I agree about the capacity of phone batteries. The trouble is that manufacturers seem to count the thinness of their phones as paramount. Howsabout we start a campaign for phones to be 1mm thicker with higher-capacity batteries? Maybe there should be a standard for how long phone batteries should last.

A Nother says:
9 October 2012

High capacity battery’s!!!
Please take a look at this link’s feedback and others for high capacity battery’s,

Amazon seems to be unaware of their sellers possible misselling as the battery’s don’t seem to last any longer thsn the low capacity 1300mAh as they are nearly twice the capacity.
They are the same size and charge up in the same time too, how’s that more than the low capacity.
Whats the chance of you taking a look into this please.

I don’t think Amazon tests the batteries they sell and I would doubt that any retailer does. If you are not happy with a product then ask for a refund/replacement. With Amazon and some other online retailers you can leave feedback to warn future purchasers. Unpopular products are likely to be replaced, though that does not guarantee that the replacement products will be any better.

This discussion is intended to be about standard rechargeable batteries (e.g. AA size) rather than ones specific for a product such as a phone or camera.

photocruiser says:
27 December 2013

To get good rechargeable batteries you need to go to a specialist radio store which are few and far between. he best way to find out where they are is to go to a large Newsagents in a town centre and ask for the specialist radio magazine section. Then read the adverts in the magazine to find out where you specialist shops are. You can do the same thing on line and you can also order from the majority of these stores on line. The third and best way is to find out where there will be what they call a Radio Rally in your area, baring in mind that this could be 50 miles or more away. Like Computer Fairs they are often held on a Sunday. The last one I went to was held at a very very well known Race Course on a Sunday in the South East.. I went to the stand of a well known specialist Radio, TV and HIFI who operate in Essex. From them I was able to buy a charger and a set of batteries. I can’t tell you the name as I do not have the charger with me at this time. The results I have had have been excellent using the AA batteries they sold me. The other thing about buying at a Radio Rally is that the price I paid was very much cheaper than their shop price. My experience of Ansmann chargers is in a nutshell that they are IN MY OPINION useless. I was sold one by one of my specialist Camera stores and after a while the charger died on me. The batteries weren’t much good either. A replacement charger also died on me. The most important point however is that it depends on which PRODUCT you are using. Now I turned on one of my specialist portable radios after about 30 MONTHS and it powered up instantly! Hello! Please read again whet I have just written in the previous sentence. This product comes with an excellent Ni- MAH battery which is yes you guessed it RE-CHARGEABLE! To close, in my opinion the UK phone companies are in league with the Utility Companies and put RUBBISH batteries in phones so that one uses more electricity to keep our phones up to a suitable charge level.

William says:
26 April 2015

I also used to see these batteries at computer fairs, but the fairs stop running for the most part. They say on-line auctions and computer piracy are the reasons but I think otherwise – you are spot on about the prices. It used to be great to get goods at much better prices than the rip-off high street, and that’s the reason they closed in my opinion.. so that people are forced to buy over-priced rubbish from large retail stores or sit and wait for stuff to come off eBay etc, not knowing its real origin. p.s. One of the best AA batteries I ever seen was an industrial one I checked inside a multi-meter, I think it was a marine battery or something. I thought since the meter had been in storage for 10 years the battery might be in a state but to my surprise it was pristine.. and still had a great deal of charge left. I couldn’t believe it. The battery was all black with green lettering. I will update this when I find the unit and take it apart again so I can state the make 🙂

Johnny Bravo says:
19 November 2015

Have seen rechargeable AA batteries with a 8150mah capacity which is really good these days

Was the first digit not a deformed 3? I don’t think 8150mAh is really possible. Even 3150mAh claim would be really pushing it .

Ken G says:
2 June 2021

I think with the mass production of these batteries the manufacturer will never reach the laboratory designed capacity. For an AA sized battery currently the capacity is around 3000mAH (3300mAH is common).
Why are batteries not clearly marked with the capacity? You buy a litre of petrol or diesel from a gas station, or indeed a pint or a litre of milk from a supermarket. Why not have the capacity clearly marked on the battery’s packaging, secondary and primary batteries? Since you are buying a container which has a quantity of electrical power for your consumption. Then you can make a decision as to what specific battery you need for your application.
I would not expect to buy a litre bottle of milk with 780ml and pay for the 1000ml.