Review: Duracell 2650mAh AA NiMH

[itsme000]

Update 12/05/06:

I've had these 2650mAh AA batteries for perhaps six months and they've been through perhaps several tens of cycles. One set of four for evaluation, another set of four for my camera. The evaluation set have had tens of full charge/discharges cycles through them, but the camera set have not received many.

Most of charging is performed on Duracell brand 15 min or 30 min charger and testing on a LaCrosse BC-900.

My Eval set have developed high self-discharge and permanent loss of capacity. Two out of four are down to 2.2Ah and it loses more than half the capacity in a few weeks. They all tested around 2.67Ah when they were new. My testing shows these degrade significantly before you reach nowhere near the ~500 cycles that is typically claimed for NiMH batteries.


I purchased four Duracell 2650mAh AA rechargeable batteries. Available at Wal-Mart for $10.

In order to test these as accurately as possible with limited test equipments, I tried to simulate the test procedure used by the battery industry. (0.1C x 16 hrs, one hour rest, followed by 0.2C to 0.9 to 1v end voltage)


Charge method: 0.36A x 9 hours on a dumb, timer controlled charger.
They were allowed to sit around for an hour or two, then discharged. The 0.36A rate wasn't chosen for any particular reason. That is what the dumb charger I have available happens to provide.

Batteries were allowed to rest a few hours, then discharged.

Discharge method: 0.5A(should be 0.54, but my discharger can't do more than 0.5A), end voltage 1.0v (it should be 0.9v, but stupid BC-900 reads 0.1v lower than actual)

Test result:

2.68Ah, 2.78Ah, 2.78Ah, 2.63Ah. This is what I got the VERY FIRST cycle. Amazing!

Average: 2.72Ah. Notice that every cell's capacity is +/- 4% from the average value. This is very good.

The package says "Made in Japan" and charging instruction says "270mA x 16 hours" which leads me to believe these could be Sanyo 2700mAh. The cells lack the "-HR-" symbol on the bottom, which is consistent with the Sanyo's 2700mAh.

These are very good batteries, however I'm not implying that "Duracell" rechargeables are very good per se. The OEM source they used(most likely Sanyo) is very good.

I have some Duracell 2100mAh Made in China batteries and they're very poor quality.

Update: ok, since you don't use just one cell at a time, I tested the performance in a four cell series config. The Wh figure is for all four cells combined.

Test result
3.17watt-hour (per cell )
2670mAh
1.06oz each. Probably the heaviest battery ever.

[nimh]

Hi, Itsme000. Thanks for your post. My experience is somehow like you. Differenct OEMs have very differen qualities.

I found the Energizer's OEM in China makes very high quality 2500mAh AA battery. However the OEM in Japan makes extremely bad cells.

Here is my experience

I want to share my experience with you guys about the Energizer 2500 AA battery. I bought 4-pack Energizer 2500NiMH AA batteries from Fry's. I test them immediately using the "test mode" in La Crosse charger. They are 2560, 2590, 2650, 2600 respectively. I was very happy with them and wanted to buy more.

A week later, I found Sam's club had 8AA(2500)+4AAA(850) Energizer batteries package for only 18.99. I bought one. After I tested 4 AA cells, I cannot believe my eyes: 1650, 1745, 2100, 1682 for each. I wonder if I bought some fake Energizer (Sam's club told me those were real Energizer, I just bought defective one).

Before I return them, I compared the new bad cells with the previous 4 good cells. I found there are several diffences: the good one has black cover paper in positive, while the bad one has green cover paper; the good one has smaller positive node, while the bad one has bigger one; the good one is made in China, the bad one is mad in Japan.

I think the Energizer has two souces of OEM: one is from China, the other is from Japan. I am very satisfied with the former one from China. I will rate them as 2600mAh or even 2700mAh. For those cells from Japan, I will rate them as 1700mAh, and throw into trash bin.

That is my experience. I hope it will be helpful. I strongly recommend you the Energizer 2500 with black cover paper in positive, which is from China. NEVER EVER buy those Energizer from Japan.

[itsme000]

nimh wrote:

Hi, Itsme000. Thanks for your post. My experience is somehow like you. Differenct OEMs have very differen qualities.

I found the Energizer's OEM in China makes very high quality 2500mAh AA battery. However the OEM in Japan makes extremely bad cells.

Here is my experience

I want to share my experience with you guys about the Energizer 2500 AA battery. I bought 4-pack Energizer 2500NiMH AA batteries from Fry's. I test them immediately using the "test mode" in La Crosse charger. They are 2560, 2590, 2650, 2600 respectively. I was very happy with them and wanted to buy more.

A week later, I found Sam's club had 8AA(2500)+4AAA(850) Energizer batteries package for only 18.99. I bought one. After I tested 4 AA cells, I cannot believe my eyes: 1650, 1745, 2100, 1682 for each. I wonder if I bought some fake Energizer (Sam's club told me those were real Energizer, I just bought defective one).

Before I return them, I compared the new bad cells with the previous 4 good cells. I found there are several diffences: the good one has black cover paper in positive, while the bad one has green cover paper; the good one has smaller positive node, while the bad one has bigger one; the good one is made in China, the bad one is mad in Japan.

I think the Energizer has two souces of OEM: one is from China, the other is from Japan. I am very satisfied with the former one from China. I will rate them as 2600mAh or even 2700mAh. For those cells from Japan, I will rate them as 1700mAh, and throw into trash bin.

That is my experience. I hope it will be helpful. I strongly recommend you the Energizer 2500 with black cover paper in positive, which is from China. NEVER EVER buy those Energizer from Japan.

The LaCrosse BC-900 is not a very reliable "charger". It is well known that it can prematurely stop charging or fail to stop charging until thermal monitoring shuts it off for overheating.

I have had good experience with Energizer 2500 Made in Japan. I believe the error is in your testing. You need to let them charge in a timer controller charger or at least try charging it again in the LaCrosse charger in 200mA setting for 16 hours.

Once done charging, take them all out. Put them all back in, and put the BC-900 in "Discharge/refresh" mode and let it start discharging at 500mA. In this mode, discharging takes place first and it will remember the discharge capacity from the first discharge as long as you check on it before the second cycle is complete.

[SilverFoxCPF]

Hello Itsme,

It sounds like you are having problems with your BC-900 charger, or with your cells. While there have been several reports of thermal melt down with this charger, I should also point out that there are a lot of people that are using them without problems.

We still haven't received a good explanation of why the BC-900 thermal shut down sometimes does not work, so we have issued a series of theories in an attempt to understand this behavior. I have been using my BC-900 for about a year and a half now and have had no problems at all. There are lots of other people with similar experiences.

It does seem that the melting of the plastic in the charger has stopped with the release of version 33, so perhaps the manufacturing problems were also addressed at this time. La Crosse still refuses to acknowledge that there is any problem at all. They point out that they are not aware of any problems, and if you are not satisfied they will warranty your charger.

You have indicated that your batteries are causing the charger to shut down because of high cell temperature. This is caused by high internal resistance of the cells. Heat is generated when you overcome this internal resistance through charging. It sounds like your charger is functioning properly by shutting down the charge when the cells heat up.

The internal resistance of cells increases with cycles, hard use, and extended storage. Sometimes a set of batteries will show high internal resistance even though they were just recently purchased. This could mean that they have been sitting on the shelf for a while. Cycling will sometimes redistribute the electrolyte in a Nickle based cell and reduce the internal resistance caused by starved electrolyte. It can take as much as 50 cycles, but you should see improvement along the way.

I understand that chargers are not perfect, however it is easy to blame the charger for everything while the batteries may be contributing to the problem.

Also, keep in mind that it is recommended to charge NiMh cells at 0.5C to 1C in order to get a strong "end of charge" signal. With 4 cells charging, the BC-900 is limited to 1000 mA charge current. That is less than 0.5C for 2400 mAh cells and those of greater capacity. The alternative to"smart" chargingis to do a "timed" charge at 0.1C for 14 - 16hours. This works great if you completely empty your cells every time, but it becomes more difficult if you only partially empty them.

Tom

[E.T]

nimh wrote:

A week later, I found Sam's club had 8AA(2500)+4AAA(850) Energizer batteries package for only 18.99. I bought one. After I tested 4 AA cells, I cannot believe my eyes: 1650, 1745, 2100, 1682 for each. I wonder if I bought some fake Energizer (Sam's club told me those were real Energizer, I just bought defective one).
Before I return them, I compared the new bad cells with the previous 4 good cells. I found there are several diffences: the good one has black cover paper in positive, while the bad one has green cover paper; the good one has smaller positive node, while the bad one has bigger one; the good one is made in China, the bad one is mad in Japan.

I wonder are they really sure those are from Japan...
It's just ink on paper and in that part of world they make counterfeits from about pretty much everything.
There was even whole fake company copying NEC and making even own product releases.

Also for example I think it was here in this forum that one user had bought "original" digicam battery from eBay shop, for some reason packing of battery claimed it to be from Japan while battery had been posted from Shanghai, China. (also it was different than battery bundled with camera)

If those 2500mAh are one of those "15 min rechargeables" there might be some differences in internal structure. (charging currents required for those times are huge)

But then again those might be again faulty cells...
I had one cell among set of four 1850mAh Sanyos (with Minolta 7i) whose voltage dropped much faster than others.




itsme000 wrote:

end voltage 1.0v (it should be 0.9v, but stupid BC-900 reads 0.1v lower than actual)

How did you get that comparison voltage? If with multimeter's voltage measuring that's lousy way for measuring voltage of battery because it's literally idle voltage what's measured.
Better/more accurate way for measuring voltage would be applying slight load and that might be exactly what BC-900 does. (one multimeter I had included own mode for testing batteries, it measured voltage under 100mA load)

[itsme000]

E.T wrote:

itsme000 wrote:

How did you get that comparison voltage? If with multimeter's voltage measuring that's lousy way for measuring voltage of battery because it's literally idle voltage what's measured.
Better/more accurate way for measuring voltage would be applying slight load and that might be exactly what BC-900 does. (one multimeter I had included own mode for testing batteries, it measured voltage under 100mA load)

It's easy enough to slide a pair of wires into the gap at both ends of a cell so you're measuring the real time voltage while they're being discharged.

LaCrosse reads 75-120mV (varying depending on the actual voltage) lower than the real voltage on 0.5A discharge mode.

When the display reads "0.90V", BC-900 stops discharging. The lowest voltage recorded on my DMM is 1.016v, so in this case, LaCrosse is reading 116mV lower.

[itsme000]

data updated

[Razor06]

itsme000 wrote:

The LaCrosse BC-900 is not a very reliable "charger". It is well known that it can prematurely stop charging or fail to stop charging until thermal monitoring shuts it off for overheating.

I'm going to be buying some Duracell 2650's, and was wondering what are some of the best chargers out there...I noticed the BC-900 wasn't that reliable. Thanks

[itsme000]

Razor06 wrote:

itsme000 wrote:

I'm going to be buying some Duracell 2650's, and was wondering what are some of the best chargers out there...I noticed the BC-900 wasn't that reliable. Thanks

I don't know of a charger that can fully charge 2650mAh besides the Duracell 15 minute charger, unless you count the slow 16-24 hour charger.

The problem with Duracell 15 minute charger is that they don't come with 2650mAh batteries and its only available bunded with 2400 or 2500mAh.

[Razor06]

Hmmm, ok thanks, I'll look around for that charger.