littokala analyzer bays are suitable for 16340. skyrc and opus analyzers can't go lower than that either.
ive never heard of 18240 size. very rare is 10180 size for special .CN keychain lights.
neodymium have minimal resistance but are also the most practical solution. a copper spacer or adapter, for example, would oxidize at its surface, also adding minimal resistance. how about a spacer made out of aluminum or brass? or, you could use a nice spring from an flashlight body as spacer, e.g. AAA twisty light like Tank007 E09. They all add resistance .. but remember that connecting a 18240 thru wires/crocodile/alligator/banana to a hobby charger would add resistance too; after all, i am not satisfied with the accuracy with any hobby charger including my 106B+ iCharger, nor with littokala chargers: with repeated TEST in the same littokala slot you will have noticed that the mAh reading varies "a lot" for the identical battery, namely by about ±1.3% (or |2.6%| peak-to-peak tolerance band). Doesn't sound like much but personally i stop caring about the mAh readings at such tolerance values. Pointless to make serious use of them, note down on paper, or alike imho.
interesting topic though. i don't own sub-16340 sized batteries but i would not mind possessing an aluminum spacer; they should have less resistance than neodymium. one day i'll find something suitable, by chance, in my household
EDIT: in practice, the uncertainty is 5.2%, i.e. double of the 2.6% band. Why? Because the user does not know the real capacity. To illustrate the concept of uncertainty in a very practical situation, here an example with a "±1.5% tolerance":
1. Let's assume that an expensive piece of super accurate equipment did measure a capacity of 1000mAh. Then this is the actual capacity, the real capacity, because the equipment measured accurately.
2. "±1.5% tolerance" means that your charger LCD (littokala, opus, etc) may display anything "between" 985mAh and 1015mAh to be within spec. In reality, the LCD will display these very values and not a value "in between"! Clear and simple, the LCD will never "hit" bullseye 1000mAh because the readings are just off. Namely by 1.5% away from the actual value. (That's at least true for this product.)
3. Now let's assume you made 1 single TEST, and the LCD does report "985mAh". Then what? — The problem in practice is that you do not know where this number comes from, from below or from above!
4. From above: *If* the real capacity were 1000mAh (well, it is!), then "±1.5% tolerance" would lead to 985mAh (=1000*0.985). Okay, we got that.
From below: *If* the real capacity were 970mAh (well, it's not!), then "±1.5% tolerance" could lead to 985mAh (=970*1.015) too!
So you write down on your paper: 'the real capacity must be somewhere between 970 and 1000mAh'. Well, that doesn't sound too bad, does it?
5. But let's assume you had made that 1 single TEST and the LCD reported "1015mAh" (instead of "985mAh", see 3.). Then what? — Again, same problem. You do not know where this number comes from, from below or from above!
6. From below: *If* the real capacity were 1000mAh (well, it is!), then "±1.5% tolerance" would lead to 1015mAh (=1000*1.015). Okay, we got that.
From above: *If* the real capacity were 1030mAh (well, it's not!), then "±1.5% tolerance" could lead to 1015mAh (=1030*0.985) too!
So you write down on your paper: 'the real capacity must be somewhere between 1000 and 1030mAh'. Well, that doesn't sound too bad either, does it?
7. Wrong, that's bad. Combine the last sentences of 4. and 6. with a logical boolean OR, it will read 'the real capacity must be somewhere between 970 and 1030mAh'. That's an 'effective uncertainty band' of 60mAh on a ~1000mAh bare cell without any labeling. On a ~3500mAh bare cell without any labeling, the uncertainty band would be 3.5× as much,
210mAh. Unacceptably high for my uses.
8. Things are easier when you
know the real capacity in advance, say a 3500mAh NCR18650GA cell. In this case the uncertainty band equals the "±1.5% tolerance" band: the LCD could display 3447mAh or 3552mAh, and you would know where the number comes from. No uncertainty.
Note: the littokala "±1.3% tolerance" is something which i measured manually with my own equipment which produces more accurate and reliable mAh measurements than any given charger. opus, xtar, etc don't specify in the official specs how much the tolerance of the mAh readings is. This number is something which semi-pro testers
and reviewers must find out by repeated testings and comparisons, like i did.
(
sorry for the OT. when i find a more suitable thread, i will cut'n paste this stuff there, np )
the point of my post is i guess: using xtar, opus, or littokala analyzers for serious data collection is an exercise in vain. their tolerance bands spoils the fun and purpose.
