Sanyo eneloops, Extra Long Life In Use or On The Shelf
Written: Jan 22 '07 (Updated Feb 13 '07)
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Product Rating:
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Pros: Higher discharge voltage, keeps 85% of charge up to a year, competitively priced.
Cons: MAh capacity currently lower than standard NiMH batteries.
The Bottom Line: Not only do Sanyo eneloops hold their charge much longer than standard NiMH AA rechargeables, they run longer in most high power equipment.
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| vivona's Full Review: Sanyo eneloop AA 4-Pack Ready-to-Use Rechargable B... |
Regular NiMH AA rechargeable batteries were only giving me 10 shots in my new digital camera. A lot of testing and research led me to Sanyo eneloops. Now I get over 400 shots on a charge! The added bonus is great shelf life. Read on for the full story.
THE PROBLEM
I had bought a new Canon A540 digital camera and began testing it with a set of regular AA alkaline batteries to see how long they would last. I got the 90 mostly flash pictures claimed by Canon. So far, so good. However, when I tried a slightly used set of NiMH AA rechargeable batteries, they only ran for 10 flash pictures and the low battery indicator began to flash. I tried another set of my NiMH batteries and the same thing happened. A tried the batteries in my wife’s new A540 and got the same results.
So, I began researching this problem. I found a website that had conducted tests on AA NiMH batteries of 2000mAh or greater capacity. The test was conducted by placing 10 ohms across a 4-cell pack of 14 different brands or models of NiMH batteries. This test simulated the typical current draw of a digital camera. The voltage of the 4-cell pack was charted on a graph and the number of minutes were listed at the point where the voltage dropped to 3.6 volts which is 0.9 volts per cell and the voltage at which a NiMH battery is considered to be fully discharged. The website recommended the batteries that ran the longest before reaching the 0.9 volt cutoff voltage. The range of performance ran from a low of 137 to a high of 322 minutes.
Okay, this test would be valid if my camera considered a battery to be fully discharged at 0.9 volts per cell. But did it? I connected my camera to an external power supply and found that the low battery indicator came on at 1.1 volt per cell and that the camera would shut down at 1.0 volt per cell. I checked my wife’s camera and got the same results. So, even though the battery manufacturers consider their NiMH batteries as fully discharged at 0.9 volts, your device may have a higher cutoff voltage like my camera. That probably explains why people in reviews and user forums report such large variations in rechargeable battery performance.
Then I went back to the battery test and studied the voltage graphs. I divided the graph voltages by four to get the per-cell voltage. I saw that about half the tested batteries would drop below 1.1 volt per cell very early in their discharge cycle and stay at or below that level for the remaining time of their discharge. Those batteries would quickly cause my camera to show its low battery warning. Three of the batteries dropped to 1.0 volt or less per cell early in their discharge cycle, including the Sanyo 2500mAh (not eneloops, but regular NiMH batteries) that was rated as best according to minutes of runtime. So, if I had merely relied on that battery test and bought the highest rated battery, I would have found them to only last about 20 minutes which is the point where they dropped to 1.0 volt per cell.
THE SOLUTION
When I saw that the Sanyo eneloops kept their voltage at 1.2 volts per cell for most of their discharge time, I knew that they would work the best for my camera. I bought a set and tried them. Sure enough, I got an amazing 438 pictures on a single charge, even exceeding Canon’s claim of 360.
BUT WAIT, THERE’S MORE!
This is where we get to the more common reason you would buy eneloops. They have a great shelf life. A regular fully charged NiMH battery will lose about 1% of its charge per day just sitting on the shelf. So, if you charge regular NiMH batteries and put your camera (or other device) away for three months and then have a reason to use it, you find that the batteries have gone dead by themselves. Not so with the eneloops. They have been specially designed to keep 85% of their charge after a full year of sitting on the shelf. For the casual digital camera user that may wait months between pictures, this is a major improvement in rechargeable batteries.
Sanyo eneloops come pre-charged and ready for use. My eneloops were dated as being six months old when I opened the package. I put them in the camera without charging them and they worked fine. I took about 30 pictures to see if they would quit early and they didn’t. I then charged them with an Energizer compact charger, the little square one that has a drawer for the batteries. As I mentioned above, the fully charged set ran my camera for 438 pictures. These were mostly flash and all with the LCD on and over a period of 10 days. That means I could charge up the eneloops and take an entire vacation’s worth of pictures without having to recharge.
How do they do it? Sanyo claims that the longer shelf life is due to a high-performance negative electrode “superlattice alloy” and the make-up of battery material and battery plates. Their tests were conducted at 20 degrees Celsius and they claim the eneloops retain 90% of their power after 6 months and 85% after one year. 20 degrees Celsius equals 68 degrees Fahrenheit which is a bit below what one would consider average room temperature. Since battery life goes down with increased temperature, I would expect the actual shelf life of eneloops to be a bit less than claimed. But, since the comparison test was made with regular NiMH batteries at the same temperature, the eneloops should still have a substantially better shelf life than regular NiMH batteries.
Now, what about the fact that AA eneloops are rated at 2000mAh and most regular NiMH AA batteries are rated at 2500mAh and above? While waiting for my eneloops to arrive in the mail, I had bought a new set of Energizer 2500mAh batteries, charged them and tested them in my camera. I got 300 mostly flash pictures. So, despite the higher mAh rating, the Energizer batteries didn’t run as long as the eneloops because their voltage dropped to the camera cutoff point sooner. Only if your device has a cutoff voltage of around 0.9 volts per cell would you benefit from higher capacity regular NiMH batteries, but then you wouldn’t get the long shelf life. I also notice that the higher capacity NiMH batteries are rated at 500 charge/discharge cycles, but the eneloops are rated at 1,000 cycles, so they should last longer before needing replacement.
For more information on the battery tests, see http://www.users.on.net/~mhains/Reviews.html (I can’t guarantee how long this link will work).
For more information on the Canon A540 experience with batteries, see http://www.epinions.com/content_309290569348
Recommended:
Yes
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Epinions.com ID:
vivona
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Reviews written: 20
Trusted by: 4 members
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