Rayovc NiMH battery discharge tests

[ralphd]

While popular batteries like the eneloops have been widely tested, tests of Rayovac NiMH batteries are hard to find.  I tested 3 different Rayovac AAs and found their capacity ranged from ~1100 to 1350mAH.
I also tested a ~7yr old 1st-generation eneloop and a new Amazon Basics (OEM eneloop) for comparison.  Discharge plot attached.
More details on my blog.  http://nerdralph.blogspot.ca/2015/12/nimh-battery-discharge-tests.html

[saturation]

Your simple test also shows one thing that is kept quiet in the industry, that NiMH can have long calendar lives, I think its total life is driven mostly by charge-discharge cycling and an optimal charge curve.  At 1900mAH your 7+ yr old eneloop is still rated like new.  I have mine from 2007, its just about to start its 9th year in service and still like new too.

[eugenenine]

I tested some a few years ago and the expensive Radio Shack tested as bad as RayoVac.  It got to where I had to quit going into Radio Shack stores because I'd have to bit my tongue when the salesdroids were telling customers how much better their batteries were than others to justify their high prices.

I have some Sanyo 1650mAh NiMH that I bought in 1998 or 1999 and replaced with eneloops in 2006.  I tested the Sanyos then and they all still had over 80% of their capacity.  I started using those old batteries for kids toys and as the kids outgrew the old toys my son now uses them for electronic projects.

[ralphd]

Your simple test also shows one thing that is kept quiet in the industry, that NiMH can have long calendar lives, I think its total life is driven mostly by charge-discharge cycling and an optimal charge curve.  At 1900mAH your 7+ yr old eneloop is still rated like new.  I have mine from 2007, its just about to start its 9th year in service and still like new too.

I've noticed the selection of NiMH batteries at most Walmart is very limited now.  I suspect demand is quite low due to the long life of the batteries.

[saturation]

There are only a few online tests of charge retention of different brands of NiMH cells.  However, I worry about counterfeit of any brand moreso eneloops, and so-so quality of other legitimate brands.

 I have a 20+ stock of Tenergy LSD AA that are 1/2/cell the price of eneloop, but after several years of using them, I can clearly say they do not hold their charge over time as well as eneloop first generation.  They advertise 85%+ 1 year which I can confirm in real year-time, a spec given for 1st generation eneloop, but in side by side tests eneloop 1st generation is far over 95% charge retention. The more recent generation eneloops claim ~ loss 0%/ 2 years.

Panasonic lists its actual spec fairly conservatively:

https://en.wikipedia.org/wiki/Eneloop#Comparison

Over time I replace batteries because I lose or damage them [ e.g. falls into salt water and shorts itself to death].

I also find eneloop tolerates cold better than most other cells, easily 0C or less.

That said, I think a better bet for buying NiMH is online purchase of eneloop from reliable authorize sources or its rebadged as Amazon Basic.

[ralphd]

The eneloop 3rd generation specs say they are good down to -20C.  Its hard to find rechargeable batteries with better low-temperature specs than that.

[Ian.M]

For the benefit of anyone wanting to replicate your work with other battery brands, what was the resistance of the 3.7R load, measured at the battery holder terminals to at least 2 decimal places?