Capacity Test of Powerex IMEDION AA Batteries

By Robert • June 22, 2008

IMEDION AA Batteries Late last year, Maha Energy - the maker of Powerex batteries and chargers, introduced a low self-discharge rechargeable battery called the ‘IMEDION’. The IMEDION batteries are compatible with NiNH battery chargers and are available in 2100mAh capacity for AA size and 800mAh for AAA.

Maha states that IMEDION batteries retain up to 85% of their charge even after one year of storage (at a room temperature of 20 deg C). This claim is similar to that made by Sanyo for their Eneloop batteries (see my post on Eneloop batteries).

Maha goes on to say: “the IMEDION batteries differ from the competition in that they boast a longer lifetime as well as increased power retention under warmer environments. The IMEDION batteries can be recharged for hundreds of times and perform extraordinarily well at elevated temperatures. In addition, the IMEDIONS feature a low-impedance design and can deliver a high burst of current”.

I purchased a new set of (4) IMEDION AA batteries from EastGear. To measure their discharge capacities, I used a LaCrosse AlphaPower BC-900 Charger (see my post with tips for using this charger here). I found the discharge capacity of the IMEDION batteries out of the package to be 1,784mAh. Unfortunately, I was not able to find a manufacturing date on either the packaging or the batteries themselves. It’s clear, however, that they are usable after purchase without charging.

IMEDION Measured Capacity
Out-of-the-pack	1,784mAh
After charging	2,208mAh

After repeatedly discharging and charging the batteries until the capacity was stable (Refresh Mode), the final average capacity was found to be 2,208mAh with a standard deviation of 0.4%. The measured capacity of the IMEDION AA batteries exceeds the advertised nominal capacity (2,100mAh) by 5% giving them a slight advantage over Eneloops.

I mentioned in an earlier post that I now prefer to use low self-discharge batteries to power my Canon Speedlite flash. With low self-discharge batteries, I don’t have to worry whether or not my primary set or back-up set of batteries were charged the day before a photo shoot. Also, I have experienced performance problems with conventional rechargeable NiMH batteries often less than a year from the purchase date.

For a comparison of IMEDION batteries with other low self-discharge batteries, see information posted by Jeff Servaas.

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