Capacity Test of PowerEx 2700 NiMH Batteries

By Robert • July 7, 2006

In the quest for the perfect power source for my Canon Speedlite 580EX, I purchased a new set of Maha PowerEx 2700 NiMH rechargeable batteries from EastGear here in Singapore. Then, I measured their discharge capacity using a LaCrosse AlphaPower BC-900 charger. (See my earlier post for tips on using this excellent charger/tester effectively.)

The batteries were found to have a discharge capacity of 2,698mAh +/-2% with an end voltage of 1.45V. Maha does claim the batteries have a nominal capacity of 2,700mAh; however, they also give a minimum capacity of 2,500mAh. A previous study of lower capacity rechargeable AA NiMH batteries yielded capacities often well below their nominal capacities. Some credit goes to using the charger/tester in the refresh mode. I noticed that the batteries did not reach maximum capacity until they had been through several discharge/charge cycles.

Measured Capacity	%RSD (4 cells)	%Nominal	End Voltage
2,689mAh	2	99.6	1.45V

Looks like Maha has a winner on their hands. These batteries are bang on! They could have rated them higher and gotten away with it. Kudos to them for honesty.

Anything Robert doesn’t like about the PowerEx 2700 batteries? My only issue although somewhat picky is the labeling. The PowerEx 2500 and PowerEx 2700 batteries look exactly the same except for the small print. If you have sets of both batteries, it will be easy mix them by mistake. The handy little plastic box that comes with the batteries helps keep them together; still Maha should consider redesigning the label.

Important: The LaCrosse BC-900 charger performs [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.

PowerEx 2700 NiMH rechargeable batteries are also available from Amazon.com and Amazon.co.uk.

More batteries will be tested and added to the Battery Round-up page.

Notes: Batteries were tested using the LaCrosse BC-900 in the ‘Refresh Mode’. I used a charge current of 1,000mA (about 0.4C) and a discharge current of 500mA (about 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. The discharge current is similar to that used by the manufacturers to spec their batteries. Sometimes, manufacturers use a lower charge current over a longer time period. IMHO, not practical for routine use. And, the results are not indicative of the real world.

Robert’s Rating: