Looking for a good way to compare CR2450 batteries

I use enough CR2450 coin cells in equipment in my shop that I think it makes sense to test a few brands against each other to see which is most economical. I don't know enough about how to load different battery chemistries to test the batteries. But I was thinking about just using an LED and a resistor combination so that the battery would drain to some particular voltage in about a month. I can use a battery I just replaced because it won't power the welding hood anymore and use it for the low voltage reference. Maybe the battery package will show the supposed milliwatt hour capacity and I can test for that too. Or maybe there is an online reference to a standard capacity. Am I on the right track? Thanks, Eric

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Just hang a resistor across a battery and log the voltage vs time, maybe read it once a day. Size the resistor according to the nominal mAh of the battery.

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

Googling cr2450 MAH (milli-amp-hr) they mostly look to be the same. ~600 or 620 mah.

George H.

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George Herold

Thanks John and George. I really shoulda thought about using just a resistor as the load. I don't have any way to log the voltage over time except to measure it manually every now and then. That will probably be good enough though. Eric

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It wouldn't be hard to add a quartz analog clock to a battery tester; battery runs out, clock stops.

You could just make your dummy load a voltage divider to drop it to

1.5V for the clock if they don't sell lithium battery clocks.

Running batteries down to the point where the clock stops isn't the best thing for the battery though, but it can't be much worse than checking it when you think of checking it.

I'd try something like a red led in series with the clock and run the clock on 3V. (clocks will work down to ~.8V, and red Leeds drop ~2V) May even flash the LED when the second ticks.

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Here's a test I found. 7.5k ohm load.

TI did some testing you might find some useful info.

Also found this in a newsgroup.

For CR2450 with a capacity of >600mAh at a 0.4mA rate;

If ESR is < 20 Ohms then you have at least 50% capacity left. If ESR is > 50 Ohms then there is not much life left (20%?)

Use a 1K load and measure voltage before after and compute voltage drop in % and multiply percent of 1K as your ESR.

Capacity drops with a load < 100*ESR and rapidly with < 50*ESR Capacity increases with load resistance up to ~1000* ESR

Another company using 7.5k ohm test load.

And then for the best economic efficiency there's this.

With this usage profile, the CR2450 battery would last approximately

4.33 years. With the same usage profile, the AAA alkaline battery would last approximately 4.65 years. This duration represents 16% higher efficiency, resulting in a 7% increase in service life with a 60% decrease in battery cost.

So modify it for a AAA battery. :-)


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A 4$ arduino clone on ebay with a 3$ LCD display, a load resistor and a fre e sketch would do what you want.

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A few weeks ago I bought an Arduino clone kit from China for about $ 8. Lots of parts plus the UNO board. Could not believe how inexpensive it was. Most of the kits like like that are around $ 20. I think I do have to download a manual insted of a paper one that seems to come with most of them. Many inexpensive things are comming out of China now. Some not so good, but some that work very well. I have not received it yet, but they do seem very simple to program to do simple things and there are free sketches (programs) for many things.

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Ralph Mowery

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