NiMh AA batteries

AA batteries are a familar tool to most photographers. On-camera flashes use them (either 4 or 5 at a time). Some compact cameras (and the Fuji S2 & S3 Pro DSLRs) use them. The Canon CP-E3 external flash power pack uses 8 of them. In my own kit my GPS also uses them, along with our 2-way radios (which use 3 each).
With all these batteries, rechargeables are great and the NiMH (Nickel Metal-Hydride) ones have become the defacto standard. They can supply relatively high currents (especially compared to the alkaline cells) and are less susceptible to charging issues than NiCd cells are. Mind you, they’re not perfect for all applications. They self-discharge: their stored charge dissipates when they’re not being used (typically 2-10% per day, depending on temperature). So putting NiMH batteries in a torch that spends most of its time on a shelf or in a camera bag waiting to be used, would not be a good idea. It would probably be flat when you needed it! The Li-Ion (Lithium Ion) batteries common in most digital cameras (and mobile phones) today do not suffer from self-discharge, but they’re not available in AA size.

With all these devices using AA batteries, photographers often build up fairly large collections of batteries. How much power each battery holds is the basic feature that’s important (note that as the batteries get older their capacity will reduce: eventually justifying replacing them, or at least only using them in less-demanding devices).

Chargers
The way you recharge the batteries can have a large effect on their capacity and longevity. Obviously undercharging a battery will limit the amount of power available, but overcharging will do the same on a more-permanent basis. Charging a battery too fast can also damage it. For this reason most chargers have basic overcharge protection built-in, and limit the charge current. However many chargers do this very poorly, and it’s important to choose a good charger. Probably the most important feature to look for is to have individual charge circuits for each battery (typically with separate indicators: e.g. LEDs).
Cheap chargers offer the ability to charge only 2 or 4 batteries at a time. Unfortunately this assumes that all the batteries in the set are behaving identically. This is never true (especially as the batteries age) and the result is at least one battery ends up being overcharged, and the others are often under-charged. When one battery fails, the whole set fails (and can in fact be damaged by the charger). I recommend that you do NOT use a charger like this!
At the moment I have two favourite chargers:

La Crosse BC-900
I use this charger myself (bought from Thomas Distributing in the U.S.). It can charge up to 4 batteries at a time, and has an amazing list of features. Not only can you set the recharge rate for each battery, it measures and displays how much power was put into each battery (which makes it obvious when one of your batteries starts failing) and has a test mode where it measures how much power each battery holds.
The BC-900 runs off a 3V, 4A (!) supply from a universal AC adaptor, which means that if you want to use this charger in a car or boat you will have to use an inverter to provide AC power. I have not yet found a convenient power supply to provide 4 amps @ 3V from a 12V supply.

Maha PowerEx MH-C401FS
This simple little charger will charge up to 4 batteries. It doesn’t have all the smarts of the BC-900, but lets you select between 500mA and 1A charge currents. It runs off a 12V supply, and a car (cigarette-lighter) adaptor and AC adaptor are supplied.
It’s conveniently compact, and in my testing (on a borrowed unit) has been very reliable.

There are many other chargers out there that will meet my basic feature recommendations, but these two are ones I personally like. They both handle AAA as well as AA batteries, although the only place I currently use AAA NiMH batteries is in the cordless phones in my house (they charge their own batteries) so this hasn’t been important to me.
Some chargers will handle up to 8 batteries at once, and these may be useful if you have lots of batteries to recharge. However even when travelling with all my gear, I have been able to recharge all my batteries using just the BC-900. Having a larger charger might have been useful, but it will take up more space in your luggage, which can be very important (especially if travelling by air).

Choosing batteries
There are good batteries, and there are terrible ones. There are expensive batteries, and cheap ones. How can you distinguish them?
It’s not easy, as the only pieces of information published about each battery type are the brand and the “capacity” (measured in milliamps/hour: mAh). In fact some manufacturers specify the average capacity, some the minimum or maximum, and some just give the batteries names that imply a capacity.
I have built up a small collection of batteries over the years, and using my La Crosse BC-900 charger in mid-late 2006 I have been able to measure the capacity of all of them. I have also gathered the results of the same testing from a friend in Sydney. You may be interested in the results:
Battery Published rating (mAh) Results
Number of cells tested
Min/Max/Average
Comments
“eBay cleanskin” 2600 4 cells
594/637/597 mAh
(23% of rated!)
These are not a good choice!
GP Rechargeable 1500 4 cells
1303/1493/1391 mAh
(93% of rated)
These old cells (from 1999) are surviving very well. Even so, they have about half the capacity of the latest models.
PowerTech 1700 1650 8 cells
1356/1465/1409 mAh
(85% of rated)

These batteries are Chinese imports (bought through Jaycar in Melbourne). As can be seen their quality is a bit variable, but given their price they’ve been fairly good.

However these particular batteries are a few years old, and haven’t always been charged in good chargers. They have probably suffered as a result.

PowerTech 2000 2000 4 cells
1687/1813/1746 mAh
(87% of rated)
PowerTech 2300 2300 4 cells
1667/1763/1710 mAh
(74% of rated)
PowerTech 2400 2400 8 cells
2370/2460/2416 mAh
(101% of rated)
I use these batteries as one set of cells for my CP-E3 flash power pack, and they perform very well!
m-Energy 2300 8 cells
1668/2020/1904 mAh
(83% of rated)
JKL 2100 ? 4 cells
1853/2050/1988 mAh
(95% of rated)
LaCrosse 2000 2000 4 cells
1640/2030/1908 mAh
(95% of rated)
The average here has been dragged down by one cell in the group:
a good argument for chargers with per-cell charging circuits!
Grandcell 2100 4 cells
1690/2200/1992 mAh
(95% of rated)
Prolink 2500 8 cells
2030/2240/2120 mAh
(85% of rated)
Energizer 2500 6 cells
2470/2610/2627 mAh
(105% of rated)
PowerEx 2500 min 2300 8 cells
2330/2500/2443 mAh
(106% of rated)
Like the PowerTech 2400 batteries, I use these batteries as one set of cells for my CP-E3 flash power. I’m very happy with them!
PowerEx 2700 min 2500 4 cells
2590/2670/2635 mAh
(105% of rated)
I’ve used these batteries for a month so far, and like the PowerEx 2500s I’ve been very impressed!
The performance of all these batteries will degrade as they age, but this might give you at least a sense of their behaviour. A few brands are atrocious, many are reasonable, and some are excellent. Using good chargers is important in order to maximise the capacity and life of the batteries.
As you might guess, I quite like the PowerEx and PowerTech batteries.

Storing batteries
Carrying spare batteries, it’s important to avoid accidental short-circuits as well as to keep each group of batteries together. When swapping the batteries in a flash unit, being able to pick out the batteries as a group without having to dig around in a bag or pocket is important, as well as having somewhere to put the spent batteries taken out of the unit. Especially as Professor Murphy will do his best to make sure that you’re in a hurry whenever you need to swap the batteries!
I bundle each group of batteries together, and try to have a system where I can keep track of which group is charged and which is flat (by keeping them in separate compartments of my bags). I don’t need to keep them in separate pockets of my photo vest, as I usually only have to carry a single spare group when I’m away from my camera bag.

Some photographers bundle groups of batteries together with elastic bands, but I have found two solutions that work well for me:
  • Snap-lock bags
    These bags offer waterproof storage for groups of batteries, are available at almost any supermarket, and place no restrictions on the number of batteries in a group (useful if you use 5 batteries at a time in a Nikon SB-800 flash). They last quite a while before wearing out.
    The type I use is the GLAD Snaplock “MINI” (15×9 cm) size.
  • Battery carriers
    Available to take 4 or 8 batteries at a time, these hard-plastic cases are compact and convenient. I’ve seen two types: PowerEx-branded ones from Maha, and no-name ones on eBay. I have examples of each, and I must say I prefer the PowerEx ones. They’re only AU$3 each for the 4-cell versions. The 8-cell version is AU$4 (I use one of these to keep the spare batteries for my CP-E3 together).

Places to purchase these products
If you are in Australia and are interested in Maha or PowerEx products, I recommend talking to the Australian distributor: Servaas Products in Vermont (Victoria). If you’re in the USA, I have in the past had good dealings with Thomas Distributing.
Disclaimer
Just in case you’re wondering, while I have on rare occasions received some equipment from companies for review, this has always been on a loan basis and I get nothing out of it other than getting to experiment with the equipment for a while. Apart from equipment on short-term loan, all the equipment I use has been paid for with my own money.
All my recommendations about equipment and suppliers are based on my personal experiences
with these products and companies. I like to think I’m impartial!

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