Capacity Test of Powerex 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.
Robert’s Rating: 
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Hi,
Thanks for your review of these batteries. In addition to the Servaas ‘Low Self Discharge rechargeable AA battery test results’, you might be interested in the results of a more extensive three month comparison test of AA NiMH Low Self Discharge Batteries here –
AA and AAA NiMH low self-discharge tests–Round 2
The PowerEx IMEDION AA batteries top the ratings with the highest mAh capacity and levels at three months. Kodak Pre-Charged batteries were second (and may be cheaper and easily obtained for many), with GP ReCyko in third and Duracell Precharged AA batteries in fourth. Sanyo Eneloop is in eighth place.
There is quite a bit of activity regarding ‘Low Self Discharge Batteries’ on Candlepowerforums.com, but this link shows the AA NiMH Low Self-Discharge Test graph.
I recently purchased some PowerEx IMEDIONs and Kodak Pre-Charged AA and AAA batteries due to this test.
I found that Sanyo Eneloop performs better than Imedion, not in capacity, but in speedlight refresh rate stress test. I full charge both set of the battery, insert into Nikon Speedlight SB-800, stress test the refresh rate.
Eneloop completed at 1564 shoots and Imedion completed at 1660, approximately 100 shots more than Eneloop, which is pretty much expected as it is a 2100mAh vs 2000mAh, with approximately 5% extra power. For a fair comparison, the first 1500 shots are only taken into account, which is already beyond what average number of photos a person can take on a whole day event (with speedlight)
On cycle performance point of view, Eneloop out performed Imedion from 4rpm to 14rpm with an amazing everage of 6rpm on a consistant performance.
In this experiment, it is concluded that the Sanyo Eneloop is a better performer than PowerEx Imedion, at least on a speedlight point of view.
Full result review is published in my blog at: http://www.calvinstudio.net/?p=472
what the hell is “speedlight refresh rate stress test” ? is the word speedlight refer to Nikon Speedlight ???
thanx