I bought 10 30Q cells from a fairly respected (AFAIK) online seller (not Ebay) in the US, paying $5.10 per cell before tax and shipping. They look great. Eight of them came at 3.62 - 3.63V out of the box, and two were at 3.43V (not that that says much as I understand it).
I weighed two of them and they came in at 42.5 - 43.5g, less than the typical online figure of 48g (including the figure on their website).
How suspicious should I be?
What’s a go-to test device to see if my batteries are genuine (not metaphysical certitude—just 95% let’s say)?
As they do in the legal system, you need to have a preponderance of evidence. So you will have to check several things including weight, IR, dimensions, etc. Its not enough to simply weight it.
For what it is worth, IR changes with temperature, state of charge, number of cycles and discharge rate for the test.
As with a lot of things, getting a number is just half of it. Understanding the parameters of the test and how those parameters affect the result is the other half.
Resistance is the “resistance” to a steady state amount of current flow
Impedance is “resistance” when current is pulsed or at some frequency or possibly including the “imaginary part” of current flow. (imaginary part in the mathematical sense, ie SQRT[–1] or i )
So, resistance and impedance can be thought of as the same thing but are technically not the same thing.
@pirate joe 22: I didn’t want to give them a bad name before giving them a chance to make good. They are Battery Junction dot com. I’m quite pleased and I wrote them a thank you note.
@prototype3a: thanks. I ordered a tester that says it can measure it.
Well, I did a drain test on one of the light “30Q” batteries that I got.
I drained one of them at 1A until it hit 3V. Here is the result. 1621 mAh (I assume the counter is in mAh). (I’m going to do a second one overnight at 0.5A)
