New Sanyo 2700 AA - Only 2450mAh - Bad Cells?

[Ziemas]

I just picked up four Sanyo 2700mAh AA cells, and after a Break In charge on my C9000 they are showing up as around 2450mAh for all the cells. The package states that they have a minimum of 2500mAh.

After cycling the cells a few times I tried a Refresh and Analyze cycle at 1000mA charge and 500mA discharge and got even lower numbers.

Are these bad cells or do they need to be cycled some more to reach full capacity?

Thanks.

Z.

 

[SilverFox]

Hello Ziemas,

Welcome to CPF.

I think they are pretty normal, however you may want to run another Break-In cycle to see if you can make it up to 2500.

You can also present a good case saying that the cells are below their minimum, and see how some other cells work out.

Your choice...

Tom

 

[Mr Happy]

This is going to sound like a really odd question, but what is the temperature of the room where you are doing the testing?

The reason I ask is that I have some Eneloops that I have previously tested in the 1950-2000 mAh range on the C-9000, but when I recently tried to get the same numbers, the best result I could get was somewhere in the 1850-1900 mAh range. I tried others and they all gave the same lower readings.

Puzzled as to what might have caused the difference, it occurred to me that previously I was testing in the summer when the room was warm, and now in winter the room is much cooler. NiMH cells are temperature sensitive, and I wonder if this could explain it?

It is known that when NiMH cells are warm they are able to maintain higher terminal voltages and deliver more energy. Indeed some of the high performing cells used in RC applications only deliver their best when used literally hot off the charger.

I have not managed to find a warm test environment for my Eneloops (suggest 20 to 25 C, 70 to 80 F), but if you can find one that might be an experiment to try?

 

[Ziemas]

This is going to sound like a really odd question, but what is the temperature of the room where you are doing the testing?

The reason I ask is that I have some Eneloops that I have previously tested in the 1950-2000 mAh range on the C-9000, but when I recently tried to get the same numbers, the best result I could get was somewhere in the 1850-1900 mAh range. I tried others and they all gave the same lower readings.

Puzzled as to what might have caused the difference, it occurred to me that previously I was testing in the summer when the room was warm, and now in winter the room is much cooler. NiMH cells are temperature sensitive, and I wonder if this could explain it?

It is known that when NiMH cells are warm they are able to maintain higher terminal voltages and deliver more energy. Indeed some of the high performing cells used in RC applications only deliver their best when used literally hot off the charger.

I have not managed to find a warm test environment for my Eneloops (suggest 20 to 25 C, 70 to 80 F), but if you can find one that might be an experiment to try?

Thanks for the replies Silver Fox and Mr Happy.

The temperature in the room is about 22c. I returned this batch of cells today for four new ones. All the other Sanyo 2700 cells I have test above 2500mAh, so I guess it was just a bad batch. It just came to mind that out of the package the cells were less than 1 volt, so that my have something to do with it.

 

[SilverFox]

Hello Ziemas,

THAT was a very important piece of information that you left out...

You should have returned them as soon as you discovered that they were less than 1 volt. It would have saved you a lot of time...

Sometimes you can recover cells like that by several Break-In cycles. However, they usually never work as well as when you start with good cells.

Tom

 

[yellow]

they re pretty normal (better say good!)
those high numbers can only be achieved with very low discharge rates