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Rechargeable AA batteries actually tested! How do they compare?

These AA batteries are used in thousands of modern consumer gadgets. How do they stack up against each other?

Which ones are best for which jobs, and do they actually have the capacity stated on the label? Detailed Menu of Everything else HERE!

AA batteries - Larger | AA batteries - much larger!

To begin with I will explain two of the big failings of rechargeable AA batteries.

a) They "self discharge" even sat on the shelf, rapidly! After a week or so they are often 10 to 20 percent discharged depending on manufacturer and temperatures etc. After a month sat in your camera they may be half dead even if you never turn it on.

Some do this much more than others. But ALL normal Nickel Metal Hydride AA batteries do it to an annoying degree. If its in a heavily used device that is recharged often it doesn't matter and you never really notice. There are newer versions available that can sit on the shelf for up to a year and these are very useful for things that you don't use often. Like a torch, or can be used in clocks, TV remotes etc. Things that usually make batteries last a long time. These are sold as ready to use or pre charged rechargeable batteries.

A "Normal" rechargeable cannot sensibly be used like this as it will go dead before it should. Like a few weeks only before the TV remote fails to work properly... Or the clock stops. These newer batteries sold as "ready to use" don't suffer this problem. A common well known make is the "Enerloop battery". See photo above. Or Duracell Active Charge sold as ready to use.  These types of rechargeable battery are typically 20 percent smaller in storage capacity. But probably still have more actually left in them when you decide to use your gadget!

b) Rechargeable batteries seldom actually contain the "capacity" (or size of fuel tank) written on the side. Its all marketing. Even well known brands lie!  Or at least measure a selected cell under ideal conditions by discharging it very slowly and round it up to the nearest digit! This is the only way to get the "maximum" capacity out. Our gadgets don't do this though! So I test at a rate of 1 amp (about half C rating) as it is typical of real world usage.

A 2700mAh battery for e.g. may not really last as long as a cheaper 2200mAh one. That's why I measure and graph them carefully during a controlled discharge with a special "charger" and a PC designed to accurately measure this and other data.

This page will get longer as I acquire more cells to test. If you are a supplier or manufacturer and have any cells to submit email me for details and send me four cells... They must be AA's and in manufacturers packaging and new. Any size or type and any capacity.


I intend to do the same with NON rechargeable AA batteries on a different page. And test their recharge capabilities at the same time.

You may be surprised!  I have been testing and cycling a number of Alkaline AA batteries with reasonably good success even though it says it will explode and kill you and burn the house down if you try. But you do have to be careful.


Battery Tested = manufacturer and any other detail

Capacity claimed = Amp hours as written on the battery. E.G. 2200 mAh

Capacity Measured = Amp hours (down to 0.6v at roughly 0.5C or around 1 amp) Note, this is a fast discharge rate that will better reflect the use of digital cameras etc. It will show the difference between good and bad batteries much more clearly. But means that the claimed figure will never likely be achieved. The difference is caused by Internal resistance (next!)

Internal resistance = average during full discharge cycle. Less (lower) is ALWAYS better here. Especially for devices that consume lots of power fast!  I take at LEAST as much notice of this as I do capacity.

There is MUCH more to batteries than capacity (or claimed capacity).

Battery Tested

After 3 full cycles and charged by peak detect method and charge termination
verified visually by graph.



m-Amp hours
Figure on the side of the battery!

Capacity Measured
m-Amp hours
Terminated at 0.6v per cell and at 1000ma discharge rate

Internal. Resistance
Average over complete discharge cycle

Uniross 2700 AA

 Use for high capacity and medium / low current draw and quick use/recharge.




Uniross 2300 AA  

 Use for medium / high capacity and high or low current draw and quick use/recharge.



1736 95

Enerloop 2000 AA

 (very low self discharge long charged shelf life)
Graph here
(Pack of four tested in series)

Use for medium capacity and high current draw AND long term items.



Good for high current devices like cameras and flash guns

Vapextech 2200 AA

 Use for medium capacity and low current draw or short term often recharged items.


Not brilliant!
(several tested)


Extreme 2200 AA
 (very low self discharge long charged shelf life)

 (commonly found on eBay etc) Sold as ready to use and long stand by and slow discharge. I had 2 out of 8 cells faulty however. As long as all of yours are OK they are fine but not quite the claimed capacity. Compare to branded batteries like Enerloop or Duracell Active.




Good for high current devices like cameras and flash guns etc.

Duracell (Active Charge) Rechargeable
 (very low self discharge long charged shelf life)


Tested as a series pack of 4 cells.

Sold as charged & ready to use. Each cell measured 1.328v on opening the pack so very well balanced and closer to fully charged than the rest here (so far!) which were in some cases nearly half discharged as they were purchased.  Best battery tested so far. If only just! The Enerloop's are almost identical!


1848 77
Best yet, ideal for cameras, motors and things that are power hungry.

MUCH MORE TO FOLLOW  Testing takes about a day per battery!


Summary so far...

Non of the batteries get close to their rated amp hour (in mAh as written on the side).  The ones that get closest are the ones that a) don't make wild claims and more importantly b) the ones that are of low internal resistance. Since we are discharging them at 1000ma which is in under 2 hours.  Would buy the "name brand" ready charged slow self discharge 2000mah batteries here (Enerloop, Duracell Active) over the 2700 or bigger capacity batteries since they perform better in high drain devices, while at the same time keeping their charge for months to a year without naturally discharging themselves. But that was what I expected anyway... Nice to see that in the real results though!

Below just some pics of how I do this.

Hyperion EOS0720I NET3 CHARGER

Charger/Battery tester and analyser above was connected to my Computer and used to graph the batteries on the to give the data in the table.

Bigger  This is the graph from the 4 Duracell Active rechargeable cells. In a series pack. These were 2000mAh and long life (low self discharge) batteries. They are very good batteries for fast discharge stuff like cameras too. Recommended along with the very similar Enerloop batteries.

How we know they are charged!  A constant current is applied and the charger watches the voltage slowly rise over time. It charges for 50 seconds and then stops for ten repeatedly. It cuts off the charge when it sees the voltage is no longer rising, and actually begins to fall.  Bigger

When it stops for ten seconds the true battery voltage is read. the difference between the on charge voltage and the off charge voltage allows the resistance of the battery to be calculated by the charger too.. 




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