Robert’s Photography Blog

Photographers have learned that rechargeable NiMH batteries are the best choice to power an external flash. Charging the primary set of batteries prior to a ’shoot’ is not a problem. However, there is rarely enough time to charge the back-up sets which can sit in a camera bag for weeks or months. This can be quite a problem because of the well-documented self-discharging of conventional NiMH batteries.

SANYO Electric Co., Ltd. has developed a new NiMH battery technology that reduces self-discharge and operating voltage loss so that the batteries keep at least 85% charge even after one year. The new battery called ‘Eneloop’ was released in Japan in December 2005 in AA size. The AAA size was added to the line in late January 2006. In a break with convention, the batteries are labeled only as ‘Eneloop’ without Sanyo in the name and without a nominal capacity (at least in large font). The small print on the Eneloop AA size battery says: [2,000mAh typ/1,900mAh min]. The Eneloops are rated to withstand about 1,000 discharge/recharge cycles.

Sanyo has yet to release the batteries worldwide. There were limited quantities available at an IT trade show in Singapore in March. As the official launch in Singapore is not scheduled until June, I sourced a set of four Eneloop AA batteries (date code: 12/2005) from Yodobashi Camera in Osaka, Japan.

I used a LaCrosse AlphaPower BC-900 Charger to measure capacities (see my post with tips for using this charger here). I found the discharge capacity of the Eneloop batteries out of the package to be 1,857mAh. After repeatedly discharging and charging the batteries until the capacity was stable, the final capacity was found to be 2,105mAh with a standard deviation of 0.4%. Quite amazing! After 4-5 months, the batteries had retained 93% of their nominal capacity and 88% of their true capacity.

It is clear that Sanyo’s modifications to their conventional NiMH battery chemistry to reduce self-discharge has also reduced the battery’s maximum capacity. The Eneloop AA batteries hold about 25% less capacity than Sanyo’s newly released 2700 batteries. Perhaps the slightly lower capacity is worth the trade-off (certain applications) for such a low self-charge rate and to use them the first time without charging. Next is to see how they perform as a primary set of batteries in my Canon Speedlite 580EX.

Sanyo offers a new compact USB charger that will charge Eneloops or any AA/AAA NiMH batteries in any PC via the USB port. However, this charger is not necessary to charge Eneloop batteries. You can use any NiMH battery charger.

Any negatives? I only wish the capacity was a bit higher.

Resources:
More product photos are here.
Buy the Eneloop AA 4 Pack at Amazon.com.
Buy the Eneloop AA 4 Pack at Amazon.co.uk.
Buy the Eneloop Charger plus AA 4 Pack at Amazon.com.
Buy the Eneloop Compact Charger plus AA 2 Pack at Amazon.com.
Buy the Eneloop AAA 4 Pack at Amazon.com.
Buy Eneloops batteries on eBay.

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