Quite a topical question as many of us are or will be receiving VTC6 and 30Qs with added button tops for the Q8.
What sort of internal resistance increases would you expect to see for button top versions of VTC6 and 30Q. My unprotected GAs measure around 30-35 on my XTAR Dragon, protected Keeppower 26650 5200mAh around 45-55, but my new VTC6 button tops are measuring between 81 to off the scale (>150). Doesn’t seem right?
I don’t have any flat top VTC6 or 30Qs to compare to.
From what I’ve read, the difference in electrical resistance between flattop cell, and same cell with button top is negligible. The difference in output between two identical flashlights (slight difference in Vf etc.) is larger. I tend to believe this, but again this is only what I’ve read.
Another thing I’ve learned here by reading is that the IR measurement function of many chargers is a complete joke. Wiggle the battery and press the metal against the cell and you get different values all the time. I think with a normal decent spot weld of the button top, the cross section is sufficiently large so increase in electrical resistance is negligible.
Edit:
Not to mention, the Q8 is a popular prestigious project supervised by top notch modders who know how to get the max out of a light; if something causes unnecessary reduction in output all alarms will go off… At this point that’s definitely not the case. As a matter of fact there is a very successful group buy organised by RobertB for button top 30Qs. So i’d say don’t worry about it.
Without understanding too much about this topic, I feel that measuring capacity of the cell is much more reliable, and easier for chargers to output reliable data than measuring internal resistance.
Maybe I should rephrase the original question. If you have a flat top and button top version of a VTC6 or 30Q, what is the approximate difference (according to an analysing charger or DMM) in iR between them. Surely someone has measured this?
if the spread between your flats and buttons is that big either the rewrapper of the buttontop did a lousy job or you dont have real vtc6
the difference will be impossible to discern with a cheap chargers ir test.that its that large tells me something up too.
Problem solved - dirty contacts were the cause. Scrubbed them hard with ear buds and methylated spirits until the iR measured came down to around 20-25mOhm on all cells. They are now all perfectly matched. Another example of why we should all use DMMs and/or analysing chargers.
Just had the exact same issue with some button top Samsung 30Qs. Very high (and all different) internal resistance values (using Miboxer C4-12). I thought maybe the button tops weren’t connected properly to the cell.
I scuffed the anode ends with 400 grit sandpaper and cleaned with rubbing alcohol.
I’m now getting the same values as I get with my regular flat top 30Qs.
Thank you stephenk and BLF! I wouldnt have thought to try that (they are brand new) I get smarter everyday here
