23 February 2008

nimh batteries with reduced self-discharge

I used to be a big user of rechargeable NiMH batteries in my radios. My Eton E5 has more recently been living on alkaline batteries, and they seem to provide a much longer lifespan than the Energizer rechargeables I was using. Also, when traveling, I always packed a spare set of alkaline batteries instead of my battery charger.

Experiencing the poor lifespan of NiMH batteries in my radios led me to take action. First, I obtained a battery charger that was capable of fully charging the 2500 mAh Energizer NiMH batteries that I was using. Second, I researched the self-discharge property of NiMH batteries with the help of reader comments and some Internet searches.

While researching batteries, I learned about a new type of rechargeable NiMH battery that greatly reduced the self-discharge effect. Sanyo's eneloop batteries are one example of this new battery type, and in September 2006, I obtained a 4-pack of 2000 mAh NiMH eneloop batteries for $11.99 plus shipping.

When the batteries arrived, I immediately took them out of the packaging to measure their voltage levels with my volt meter. All of the batteries reported 1.31 volts. What happened next was not intended, but it happened. The batteries wandered around my apartment, unused, for 17 months. Well, they surfaced again, and the alkalines in my E5 just ran out. So I measured the eneloop batteries again (they all reported 1.30 volts today), then put them into my E5. So my Eton E5 is back on rechargeables, and these eneloop batteries only lost 0.01 volts after 17 months.


Jesse said...

A volt meter with no load is a lousy way to measure the remaining charge in a battery. NiMH batteries in particular have a very flat voltage/discharge curve.

Sanyo claims that Eneloops will retain about 85% of their charge after 1 year. Using faulty extrapolation, you probably had 80% of the full capacity left.

Anonymous said...

Costco sells a good charger+battery combo for the Eneloops.

Anonymous said...

Dear Cobalt Pet,

Today, 2-29-08, the Eton Sound 100 is selling for $39.99 on Amazon.



weatherall said...

Anonymous: thanks for adding your comment. I haven't looked around at eneloop prices or battery+charger combos recently.

Herculodge: I appreciate the tip! I misread your comment the first time around, thinking that you wrote the E100 was $39.99. So I searched Amazon for the E100 and didn't find it at that price (obviously).

weatherall said...

Jesse: thanks for explaining that.