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Robert has read claims that PowerEx 2500 AA NiMH rechargeable batteries are conservatively rated or under-rated with respect to their nominal capacity. These batteries are being advertised as the best in their class. Marketing phrases such as “ultra high performance” and “true capacity plus” are being used by distributors and dealers. On Maha’s website, they state: “PowerEx AA NiMh 2500mAh Rechargeable Ultra High Performance Batteries have 2500mAh true capacity”.

Eastgear in Singapore just received a new shipment of these batteries from Maha in Japan. Being of a curious nature, I decided to put a set of four of them to the test. I used the same procedure and settings that I used to test the Sanyo 2500 and Sanyo 2700 batteries (see my earlier post). With my standard settings (charge/discharge current of 1,000mA/500mA), the PowerEx batteries gave a measured capacity of 2,335mAh +/-3%. Then, I tried changing the charge/discharge current to 500mA/250mA. With these settings, the batteries gave a measured capacity of 2,395mAh +/-1%.

Measured Capacity	%RSD (4 cells)	%Nominal	End Voltage
2,335mAh	3	93.4	1.42V

Have I messed up somewhere? I don’t think so. Results from capacity tests of the PowerEx 2500 batteries have been posted on the CandlePower Forums. In a more extensive study, a frequent contributor by the name of SilverFox found the capacity of the PowerEx 2500 batteries to be 2,316mAh using a discharge current of 500mA. Also, in Dave Etchells’s The Great Battery Shootout, he routinely measured rechargeable battery capacities below their nominal capacities. Any misrepresentation? Of course not – read the small print!

Important: The LaCrosse BC-900 does its discharge measurement in the Refresh Mode immediately after fast-charge termination, which means there’s still a little bit of capacity left that could be filled by extra time spent trickle charging. The capacity could be boosted by an additional 50mAh or more by leaving the battery on tickle charge for an hour or so after the initial charging is finished.

Notes: Batteries were tested using a LaCrosse AlphaPower BC-900 in the “Refresh Mode”. I used a charge current of 1,000mA (0.4C) and a discharge current of 500mA (0.2C). Capacity (C) is measure by discharging the battery to an end voltage of 0.9V under constant load. Batteries were repeatedly discharged and charged until the capacity was stable (normally 2-3 cycles). These parameters should simulate normal use – medium/fast charge and a discharge period of about 5 hours.

The PowerEx 2500 batteries are also available at Amazon.com.

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