Sanyo 2500 self-discharge

[Curious_character]

I have four Sanyo AA 2500 mAh NiMH cells of the latest type -- with the colorful labels. I properly formed them when I first got them, and they have only a few cycles of use. They were normally charged at around 1A with a Maha C9000 charger, and I don't believe I've abused them in any way. I just ran a one-week self discharge test of all the non-low self-discharge cells I have, and discovered that these cells self-discharged by about 25% in one week (temp. ~65 - 70 F), while most of the others averaged around 6%. So if they sit for more than about a week at room temperature, or less than a week at higher temperature, their available capacity is less than a 2000 mAh Eneloop.

I know the early high-capacity NiMH cells developed very high self-discharge rates after a while -- I have quite of few of those -- but I figured they'd fixed the problem. But it appears they haven't. I've converted over nearly entirely to low self-discharge cells, but picked up a pack of the Sanyo 2500s for occasions where I'd be using the cells soon after charging and wanted a little extra capacity. But with the extreme self-discharge rate I'm seeing, I don't consider it worthwhile, and won't be using them.

Are other people seeing this very high self discharge rate for the Sanyo 2500s or other modern cells?

c_c

 

[paulr]

Sanyo 2500's are notorious for this. They claimed it was due to some bad manufacturing batches but it seems much more widespread.

 

[SilverFox]

Hello Curious character,

I only have a few of the 2500's left. I just checked and now have 2 more that have developed high self discharge rates.

I may be wrong, but I believe the batteries are produced in large batches. You may have gotten some from the same batch, even though you just recently purchased them. I think they jumped over the 2500 cells and moved on to the 2700 cells.

Tom

 

[GarageBoy]

Are the 2700s any better?

 

[MrAl]

Hello,

This is why i have been telling everyone to give up on the 'big' sounding
batteries and switch to Eneloop or another brand of low self discharge.
You'll be happier in the long run.

I've never seen any product so badly labeled as NiMH cells. We've seen
1500mAh cells, then 1800mAh cells, then 2000mAh cells, etc., etc., but
once the numbers get above 2200 they dont reflect the cells basic ability
to work as well as expected anymore. The higher and higher numbers just
seem to be misleading in the long run.

 

[Curious_character]

Hello Curious character,

I only have a few of the 2500's left. I just checked and now have 2 more that have developed high self discharge rates.

I may be wrong, but I believe the batteries are produced in large batches. You may have gotten some from the same batch, even though you just recently purchased them. I think they jumped over the 2500 cells and moved on to the 2700 cells.

Tom

Tom, thanks for the info. I bought them something like 4 or 5 months ago.

I have some Sanyo 1000 mAh AAAs of about the same vintage, and older 900 mAh AAAs. The 900s didn't do very well, losing 11 - 15% in one week, but the 1000s are about as good as any, 6 - 7%. Maybe they'll deteriorate with time, though. Some old 2500 mAh Sanyos I had lost 60% in a week. That's the problem I thought they'd fixed, but apparently they haven't.

I'd been a fan of Sanyo batteries for a long time, going back to early NiCd days, and love their Eneloops. But after this experience with the 2500s, I'm sure not inclined to buy their 2700s. Or for that matter anyone else's non-low self discharge cells.

c_c

 

[Handlobraesing]

I've got same issues with Duracell 2650 too

 

[Bones]

Tom, thanks for the info. I bought them something like 4 or 5 months ago.
...

If you can find a date code on the cells, it would be interesting to know when they were made.

Sanyo's date code usually consists of 6 characters indented in the label along the side of the cell.

The first two characters, which should be numbers, usually represent the year, and the second two, which should again be numbers, usually represent the month.

 

[bob_ninja]

I got some Powerex 2700 after Sanyo 2500
I found it interesting that just by holding them without measuring weight Powerex cells are significantly heaver. Others found Powerex to have a decent (low) SD.

 

[SilverFox]

Hello Bones,

I was able to find this marking on my cells...

0 5 10 SM

Tom

 

[Curious_character]

My bad ones are marked 06-04. Maybe I've had them longer than I thought!

c_c

 

[Bones]

...
I think they jumped over the 2500 cells and moved on to the 2700 cells.

...
I was able to find this marking on my cells...

0 5 10 SM

...
My bad ones are marked 06-04. Maybe I've had them longer than I thought!

Many thanks for posting these manufacturing dates SilverFox and Curious_character.

If Sanyo codes these cells the same as the Eneloop, then SilverFox's cells were manufactured in October of 2005 and Curious_character's in April of 2006.

Although it never occurred to me until SilverFox stated it earlier in this thread, Sanyo really may have jumped over the 2500mAh cells and moved on the the 2700mAh.

I couldn't find any for sale at ThomasDistributing, and the only ones I could find for sale at Amazon are bundled with a charger ...