Sanyo Eneloop

Dec 19 2006 (Updated Mar 10 2007)



Over the years I've accumulated a dozen Nimh rechargeable batteries to power-up the plethora of electronics I have. And I trusted no other company than Energizer to get the job done. Recently, several of the cells I have won't hold their charge any longer even after repeated charging. Time to buy a new set I thought. What bothers me is that I've only charged them less than fifty cycles, far from the 1000 cycle life claimed by Energizer. Other cells, while still able to take charge simply can't power up my digicam. I can still use them in less power-hungry devices but just not my camera.

I use my digicam on occasion. I take a couple of shots a month when I sell something on ebay and then the camera goes back in the closet. Often I find the batteries low on power just when I need them and end up waiting a couple of hours as they charge. I think I've charged my batteries more often than I've gotten any use out of them. Most of the time they just sit in the device self-discharging. This is one reason I wished there was a rechargeable lithium-ion AA batteries since they are known for their low self-discharge rate.

A year ago I read about the Sanyo Eneloop batteries where it was already available in Europe and Asia. It's a Nimh rechargeable battery, but Sanyo re-engineered the composition a bit to make it more efficient. I won't go into technical details what they did but what had me interested was its slow self-discharge characteristic. Sanyo claims the eneloop can retain 85% of its charge for up to a year. Wow, I said to myself. My Energizers can’t even do that in two weeks.

The Eneloop will come precharged out of the package so consumers can use them immediately without charging. They are rated at 2000 mah which may be a let down for some people considering higher capacities are available. I read that due to the unique composition of the Eneloop they can only be manufactured up to this capacity for now. I’m not concerned as long as the improvement in shelf-life is true.

I finally had the chance to purchase the Eneloop here in the US. I decided to get the kit with four AA cells and a charger for $18. Four AA cells alone are only $10.

The first thing I did was take a multimeter and measured the voltage of each cells. They were at 1.306 volts out of the package. I continued to pop them in my digicam and was happy to see it turn on.

Update (3/10/07):

The batteries have been in my digicam for ~2.5 months. Every couple of weeks I test if the camera still powers-up and so far it has. The batteries have not been recharged and still running on their factory charge.