Over the years, we periodically test and investigate alkaline D batteries for capacity and series resistance. That’s because they form the heart of many of our renewable No. 6 products. Thus, our products will work better when powered by the best battery technology available. And this translates into longer run time for our customers’ clocks, which are powered by our products.
For the most part, we have found that Duracell have been the best performance alkaline D batteries we have found, and we now recommend them for use with all of our products. But what’s this? A new contender seems to have come on the scene recently which is starting to challenge the supremacy of the Duracell alkaline D performance.
You may recall that at one time we strongly recommended Energizer alkaline batteries. Unfortunately, we’ve had some rather difficult experience with Energizer alkaline D batteries over the last few years and have dropped them off our list of recommended cells. The problem occurred first with the Model 1900W products, where impulse performance was needed (once per minute driving master or secondary clocks). We found some Energizer alkaline D batteries were turning up with over 10x their specified series resistance after a rather short 4A-hr run, which cripples them in virtually any application from powering flashlights to powering our products. Series resistance is critical to battery performance.
Most recently, we have been testing the Evergreen alkaline D battery against the Duracell Copper Top alkaline D battery. So far, here are the results:
- Evergreen shows 70% lower initial series resistance (0.140 ohms for Evergreen vs. 0.238 ohms for Duracell)
- Evergreen has 17% lower series resistance after a 9 hr run with 3 ohm load to Duracell
- Evergreen terminal voltage is 4% higher after a 9 hr run with 3 ohm load vs. Duracell
- Duracell 30 hours at 3 ohm load to 1V open circuit, vs. 21 hours for Evergreen (edge goes to Duracell)
More data is on its way, but at this point it appears we should give serious consideration to the Evergreen cells. The series resistance (again, critical for any application) appears to be better on the Evergreen, although run time longer on Duracell. However, in some applications (like ours) the better series resistance might just result in better run time!
Who is Evergreen? Ten years ago, our testing of Chinese battery technology showed a generally inferior product. However, it is well known that the Chinese have invested and continue to invest heavily in developing battery technology. Chinese LiFePO4 cells have taken a leadership position in the industry. In fact, our Model 1900R3 uses Headway technology (Zhejiang, China) and it continues to prove impressive. Ten years ago this was not the case (this improvement does not apply to all Chinese battery makers). Several Chinese lithium cell suppliers continue to advance as the premium source around the world. Evergreen alkaline D batteries are produced by Chung Pak in China. They are once again well known for investing continually to improve their factories and capability. They are ISO9000:2000 quality certified and strive to provide the best battery technology worldwide.
So, the data shows that the world of batteries is once again changing. Duracell continues to be the leader with a slight edge on run time, but remember that series resistance can accelerate how quickly a battery becomes unusable, making it a very important aspect of battery performance. And Evergreen appears to have a slight edge on series resistance over nearly half of the run time.
This does not represent a comprehensive test of all Chinese alkaline D batteries, so buyer beware of other brands.