Voltage of NiMH Cells over Time

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AA Cycler
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Voltage of NiMH Cells over Time

The open circuit voltage of some NiMH cells tracked over longer period of time… I thought it was interesting, so here we go…

X axis = days, Y axis = milliVolts

The VARTA cells are weird, aren’t they?

Cheers,
Oskar

Cycle count tests of AA batteries - http://aacycler.com

Edited by: AA Cycler on 09/10/2017 - 07:20
WalkIntoTheLight
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Interesting. I’ll add one informal data point. After charging some new regular Eneloops 3 years ago, I took them out of storage a week ago and they were 1.31v. Uncharged ones the same age (still in package), were closer to 1.30v. IIRC, they were 1.32v when I bought them. I didn’t do any capacity test.

So, I think the regular Eneloops really flatten out at around 1.32v, and lose voltage very slowly after that.

Those Varta cells are probably not LSD, which is why they drop so much quicker.

snakebite
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i just checked a 2008 pack of duraloops.
got them in 2010.
they were 1.34 each.
today 1.31 each.
never opened other than poking the sharp probes of the fluke 73III through the blister.
wish i had thought to do a 1khz impedance test with the dick smith when i got them.
rise in esr=degradation.
methinks the rating of the lsd was VERY conservative.

Tinderbox UK
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Do you have an Tronic LSD AA 2300mah cells from as they are cheap as chips but i dont think they hold their voltage very well, they sell them at Lidl stores.

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ChibiM
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Very interesting! 

How/when did you measure them? every day?

Are they all new,unused cells?

AA Cycler
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ChibiM wrote:

How/when did you measure them? every day?


Are they all new,unused cells?

Yes, all cells are new. I “broke them in” with 3 full discharge-charge cycles (0.5A discharge, 1.0A charge) before I started tracking their voltage. That’s all the use they got.

The 1st week I measured the voltage every day, the 2nd-3rd week every 2-3 days, after that only once a week…

I have plenty of unused “left over” cells from my aacycler.com tests, like IKEA LADDA 2450, Amazon Basics, etc… I think I will start tracking their voltage as well. I will update the graph when I get some meaningful data.

Cheers,
AA Cycler

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AA Cycler
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Tinderbox UK wrote:

Do you have an Tronic LSD AA 2300mah cells from as they are cheap as chips but i dont think they hold their voltage very well, they sell them at Lidl stores.

Yes, I happen to have some unused Tronic eco 2300 cells. I will add them to the mix, starting tracking them this weekend…

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AA Cycler
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Another set of 8 cells

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AA Cycler

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AA Cycler
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It’s been more than a year since I started tracking the 2nd set of cells. Now the 2nd graph is complete.

From self discharge point of view the worst cells are everActive Professional Line 2600 followed by VARTA 2400, Ansmann 2100, VARTA 2100, etc. The best are Eneloop, Fujitsu White, Fujitsu Black, Eneloop Pro, LADDA 2450, etc…

I don’t think I am going to do a 3rd set of 8 cells, it just takes too long Smile I am thinking of a quicker way to asses the rate of self discharge, I will test it first and post the results here…

I hope this was interesting.

Cheers,
AA Cycler

Cycle count tests of AA batteries - http://aacycler.com