Maha Powerex failure

[etc]

Maha Powerex AA cells, 2700 Mah

Had them for about 1.75 years.

Had an 8 pack charged a few months ago (2-3). Tried it in a Canon digicam that takes 4xAA. Worked in it before, but not this time! Tried the 2nd set of 4AA, the same thing. The camera again says "Change the batteries".

I know they don't discharge that quickly. Tested the voltage, all around 1.31V.

Tried a set of Eneloops, the camera fires right up.

What's up with that?

Are the Maha cells old?

 

[Hitthespot]

Maha Powerex AA cells, 2700 Mah

Had them for about 1.75 years.

Had an 8 pack charged a few months ago (2-3). Tried it in a Canon digicam that takes 4xAA. Worked in it before, but not this time! Tried the 2nd set of 4AA, the same thing. The camera again says "Change the batteries".

I know they don't discharge that quickly. Tested the voltage, all around 1.31V.

Tried a set of Eneloops, the camera fires right up.

What's up with that?

Are the Maha cells old?

I am not sure I'm reading your post correctly but it sounds like you charged 8 batteries as long as three months ago. Are now trying to use them in your camera. Three months ( in my experience) is long enough for non-LSD batteries to lose their charge. Eneloops will hold 85% of there charge for a year.

Bill

 

[coppertrail]

I've found the Powerex 2700, in terms of self discharge rate, to be between standard NiMH cells and the LSD cells. I charged up a set of Powerex 2700s on Sept. 19th (day before my sister's wedding) and took a decent number of shots with them at the wedding.

I pulled the cam out yesterday and my camera was showing 70% left, which is pretty darn good for non-LSD NiMH cells sitting unused for almost 4 mo.

But, at 1.31V, those cells have juice left in them, they're not dead. This is what confuses me. That's actually about where they should be after 3 mo. storage, based on my experiences.

Also, you've had these cells for 2.5 years. Have you run them through any kind of conditioning/refresh/break-in mode since you've owned them? I would definitely start there if you've not done so.

Have you tested them in any other devices? Could it be an issue with your camera not liking these cells?

Based solely on what you've posted, the cells themselves seem fine. What kind of charger are you using?

 

[45/70]

This sounds like voltage depression, in my experience. I would do a few refresh cycles on them. If that doesn't work, do a forming charge and a slow discharge, and see if that helps. Voltage depressed cells are hard to revitalize. It may very well be they are just EOL. They will still work in lower drain applications though.

Dave

 

[Black Rose]

Tested the voltage, all around 1.31V.

Is that 1.31V under load or open circuit?

 

[Marduke]

Maha Powerex AA cells, 2700 Mah

Had them for about 1.75 years.

Had an 8 pack charged a few months ago (2-3). Tried it in a Canon digicam that takes 4xAA. Worked in it before, but not this time! Tried the 2nd set of 4AA, the same thing. The camera again says "Change the batteries".

I know they don't discharge that quickly. Tested the voltage, all around 1.31V.

Tried a set of Eneloops, the camera fires right up.

What's up with that?

Are the Maha cells old?

non-LSD NiMH cells discharge approximately 30% per month. Combine that with your 2-3 month storage, and I think the probable issue is somewhat apparent. They need charged...

 

[etc]

Is that 1.31V under load or open circuit?

OC, just tested with a voltmeter.

 

[etc]

This sounds like voltage depression, in my experience. I would do a few refresh cycles on them. If that doesn't work, do a forming charge and a slow discharge, and see if that helps. Voltage depressed cells are hard to revitalize. It may very well be they are just EOL. They will still work in lower drain applications though.

Dave

My Vanson speedy charger can do that, I think. I will try it.

 

[SilverFox]

Hello Marduke,

You are only partially correct in your figures...

The average self discharge rate is around 1% per day. I have noticed that most of the cells that I use are a little less than that at 0.7% a day.

Using 1% a day for ease of use in an example, you have to remember that you loose 1% of the remaining capacity. Your numbers would be close if you lost 1% of the initial capacity, but that is not the way it works.

You start off at 100%,
at the end of 30 days you have about 74% left.
at the end of 60 days you have about 55% left.
and at the end of 90 days you have about 40% left.

I agree that at the end of 3 months they probably need to be charged, but with 40% of their initial capacity left they should still be able to work in the camera.

I should also point out that my figures are based on short term testing, then extrapolated out to longer terms. Actual long term testing suggests that my figures are a little pessimistic.

NiMh cells in storage should be given a charge/discharge cycle every 30 days to keep them vibrant. If you don't do this, you end up having to run a few charge/discharge cycles on the cells to bring them back up to good operating condition.

Tom

 

[etc]

They were charged about 8-10 weeks ago, max.

I am reconditioning them with VAnson speedy charger. I already see something is wrong: It's taking forever. Put them in last night and were still charging this morning, when I unplugged them, afraid to leave them alone in the charger.

In my experience, they should

They did not get very hot...