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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?

Comments
Member

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.

Member

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.

Member

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

Member

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.

Member

Hi wavechange, when we test batteries for charge retention we do charge them up and run them down a couple of times first (and calculate each individual battery’s average capacity) before fully charging them up and then leaving them for 25 and 50 days. We can then calculate how much of their capacity they have lost during these periods. In our latest tests the worst batteries had lost 28% of their capacity after 50 days, and last year the worst had lost 56% within the same period. Agree it would be frustrating to have charged up all you batteries then find they’ve lost half their charge when you go to use them!

Member

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.

Member
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.

Member

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.

Member
William says:
26 April 2015

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