important considerations when AA rechargeable batteries

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There are several considerations when shopping for AA rechargeable batteries.

1. Battery Capacity
When shopping for rechargeable AA batteries, buyers should be aware that there is no policing of claimed battery capacities, and some less than reputable brands claim higher capacities than actual capacity. With the development and release of a consumer level battery analyser (the Powerex MH-C9000 analyser) many users have tested their battery capacities, and found the true capacity of AA rechargeable batteries is much less than was claimed.

As of January 2010, the highest measured capacity of AA rechargeable batteries is around 2700mAh.

Several independent AA battery capacity tests have shown this to be the case, see
http://www.rechargeable-battery-review.com/consumer-batteries/aa-battery-tests/aa-nimh-battery-performance.html
and http://photography-on-the.net/forum/showthread.php?t=677074

There are a wide range of batteries on the market. Many cheap batteries do not meet 70% of their claimed capacity when brand new, and the purchaser is unaware as to why their devices are not performing as well as they should. If you find your existing batteries are not performing as well as you expected, consider testing their real capacity using a  Powerex MH-C9000 analyser to determine if the capacity is lower than you expected.

2. Battery Self Discharge Rates
High quality NiMH rechargeable batteries will self discharge at 0.5% to 1% per day. Low quality batteries will discharge at 2% to 5% per day, meaning that if the batteries are not used within a few days, they will be flat when you try to use them. This self discharge characteristic means that NiMH rechargeable batteries are ideally suited to electronic devices with high energy requirements, such as Digital cameras, external camera flashes, remote control cars, and LED torches.

3. New Low Self Discharge battery technologies
in 2006 a new type of rechargeable battery was brought to market. Using a different internal structure, Low Self Discharge batteries have about a 20% a lower initial capacity, but have a self discharge rate of only 15% per year, meaning they do not go flat before you use your device, and are always ready to use. For photographers who are taking less than 300 photos per month, low self discharge AA batteries will provide the user with more photos per set of battereis. For enthusiast and pro photographers, high capacity batteries will provide more shots per battery charge.

Real world self discharge results have shown that not all brands have the same capacity, nor do they all discharge at the same rates. See http://forums.dpreview.com/forums/read.asp?forum=1023&message=27782625 for real world capacity measurements of AA and AAA Low Self Discharge batteries at 1 hour, 1 week, 1 month, and 3 months.

4. Battery Quality
3. Cycle life
After a number of charge-discharge cycles, batteries lose some of their charge capacity. The self discharge rates also increase as the number of charge discharge cycles increase. r. How soon they lose their capacity and their charge retention depends on the quality of the construction of the battery and the quality of the materials used in the construction. We have seen 6 month old batteries which completely self discharge within 2 days. High quality batteries will still have 90% of their capacity after 100 charge-discharge cycles. Conversely, a poor quality cell can completely self discharge in a week, after just 10 charge-discharge cycles.

The country of manufacture is a good indication of the quality of batteries. In our extensive battery capacity and battery discharge rate testing, and having read other independent capacity tests and self discharge tests, we have found Japanese made batteries are currently the highest capacity AA batteries in the world. Taiwanese made batteries can also be very good, with Chinese made batteries having a wide range of capacity, self discharge, and expected recharge cycles.

When choosing batteries to power your devices, consider the warranty the company offers on their batteries as an indication of the lefe expectancy. Many battery companies will offer no warranty, or 3 months warranty, with the best offering 1 year (such as  IMEDION 2100mAh Low Self Discharge AA batteries ) and up to 5 year warranty (on  Powerex 2700mAh AA batteries ).

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