I was just checking out the Samsung spec sheet on their 30Q ( link )
It shows the expected IR to be 15-30-ish.
I got a stack of these on a Banggood coupon and put them all through a full cycle on a Zanflare C4. The capacities are right on if not a touch above rated, but the IR my charger measured ranges from 50-120 with one oddball at 220. ( Banggood Product link )
Is it more likely that my charger measurements are off, or that I got dodgy batteries, or can this all be explained by them being button tops?
(side note - the same charger measured 4 “Sofirn” 21700 at 22, 26, 30 and 36, so it can measure low IR)
Has anyone else checked the IR on their 30Q? What tester and battery source?
Did you try to get it from the charger and on the charger again?
I had it last week witch new cells, one was reading over 100 mr, placed it again, now it almost had the same value of my other new cell 22mr or so.
Probably just a sub-optimal contact
I haven’t had good luck with button-top 30Q’s from Banggood. Out of 9 purchased, 3 went “bad” within a year, and they only had maybe a dozen cycles on them. They suddenly developed very high self-discharge, losing about 5% - 10% capacity per day.
OTOH, I’ve had good luck with flat-tops from Banggood (many 30Q’s, and some other models). All of them are still going strong.
The button-tops appear to be genuine 30Q’s under the wraps, but of course I can’t be 100% sure. I think they’re sub-standard cells, at best.
I don’t know who supplies the button-top 30Q’s to Banggood, but they should get another supplier.
18650 cells are not manufactured with button tops, they're added by a 3rd party. This can be well done with proper spot welds, or can be a botch. In case of a botch the added resistance incurred by the button top usually means disaster, i.e. the discharge performance of the cell will drop considerably.
Also, button tops cover one of the most characteristic traits of cells: their flat top geometry. This makes it easier to fake cells to the ignorant crowd. Scammer 3rd party suppliers can buy cheap and readily available cells from some chinese OEM. They unwrap them, spot weld a button top on and then rewrap 'em with a different, illegitimate fake wrap which resembles that of a 1st brand cell. Done. For more information take a look, for example, at LiitoKala cells in AliExpress (they also sell fake flat top cells; this just proves how unaware is the people buying them).
Another thing you must understand is that cell internal resistance usually ranges from small to super small. When very contact resistances are in such order of magnitude, it can be easy to understand that accurate internal resistance measurement needs special methods which analyzing chargers do not possess yet (voltage measurement right at the battery terminals). Yet one can get a good clue with a proper device, though.
On my Miboxer C2 4000, the IR of buttontops can vary wildly and almost always read very high. Various theories have been stated here in the past as to why buttontop’s IR read so drastically different on analyzing chargers but for whatever reason, it’s a common thing. I find that adjusting the position of the cell in the charger can juggle the difference in milliohms by 100 or more. I’ve always purchased from reputable dealers and its still the same thing.