EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: edavid on November 20, 2015, 05:16:12 pm
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Is it possible to judge CR2032 cell capacity based on open circuit voltage?
The datasheets I've looked at are extremely vague, listing open circuit voltage ranges like 3.0-3.5V. However, this contradicts my experience, where new fresh cells always measure 3.30-3.35V, and old used cells are down around 3.0V.
Is it really possible to have a full capacity cell with an open circuit voltage of 3.0V?
What's a good acceptance test for CR2032s?
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What's a good acceptance test for CR2032s?
I'm going to guess reputable brand and fresh package date?
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I test cheal CR2032s with a blue LED. Below 2.8V under load is usually bad.
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I remember seeing a paper that described how to determine SoC of various cell types by open circuit voltage.
It involved giving the cell a few days of rest, measuring with a high impedance meter and doing some very chemistry-dependent math.
So i guess it's possible, but it's not anything straightforward.
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When it's really cold.
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What's a good acceptance test for CR2032s?
I'm going to guess reputable brand and fresh package date?
No, that's no substitute for a test. Anyway, bulk cells from a distributor don't have a date.
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I remember seeing a paper that described how to determine SoC of various cell types by open circuit voltage.
It involved giving the cell a few days of rest, measuring with a high impedance meter and doing some very chemistry-dependent math.
So i guess it's possible, but it's not anything straightforward.
I think that must of have been a paper about rechargeable cells. None of those issues are relevant to a simple acceptance test on a primary cell.
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No, that's no substitute for a test. Anyway, bulk cells from a distributor don't have a date.
Then I think you have to make your own definition of what is acceptable. For instance, specify the source and part number of the cells you will be buying, obtain some samples, test them, record the results of the tests. To test: measure the open circuit voltage on receipt, run a controlled discharge test to verify the capacity and freshness of each cell thus measured, eliminate bad cells from the data, determine mean and variance of good cells' voltage over a suitable sample size.
Having done this, use the expected voltage to test purchased cells. If the source of the cells ever changes, reestablish the metrics by repeating the sample analysis. Bear in mind that cells from different sources can have variations in cell chemistry that will change the measured voltage. They may all be "lithium/manganese dioxide", but there are many details that may be varied within that scheme.