With these DIY buttons, the button is held onto the cell just with friction/compression of the second shrink wrap that is added.
But my question is the opposite:
I bought some Samsung 30Q button tops and my understanding is that Samsung does not produce button tops – instead some secondary manufacturer/retailer will install the button and add a shrink wrap. In these cases, is the button installed in the same way – just with friction/compression holding it on?
Or do “official button top installers” spot weld their button tops?
I would peel this shrink wrap off of the button top 30Q I’ve currently got in my light, but for two things:
1. I took a bunch of extra batteries home from work last week (went on vacation) and forgot to bring them back today, so I only have this one single 18650 cell.
2. If something went wrong during the shrink wrap removal (like a short), I’d have lots of questions to answer here at work - they would NOT appreciate it.
So I will pull off the shrink wrap and find out, but it will have to wait until tonight when I’m at home.
They are spot welded . Even the 30Qs i’ve got from banggood .
I tried without welding (OP mentioned how) and it doesn’t work as good , there was a huge loss in current passing through (they were not making solid contact) .
None of the manufacturers make button tops or protected cells. 3rd parties add the button tops and/or protection circuits.
The unprotected LG MJ1’s and Samsung’s I own, all have the buttons welded on. Although, I have made some button tops using the FT parts without being welded, and they work just fine.
sac02,
would you mind defining “name-brand” as it relates to this thread?
Because I have some 18650’s that do have a name on them but are not “top tier” name-brand.
Don’t want to mention batteries that are not relevant here.
Thx
I was making a battery pack recently from 4 18650’s and when I began to solder the connectors to the tops, to my surprise, the button tops all started moving around. Bottoms were loose and apparently were added buttons as well.
When I said “name brand” I wasn’t referring to any particular brand. Basically I meant any of the large “top tier” brands out of Japan: Panasonic, Samsung, Sony, Sanyo, LG
Just checked an EagTac protected 3500 mAh 18650 I have here on my desk, and the button top is spot-welded to the flat top of the (presumed) Sanyo NCR18650GA.
Seems to work fine, although I do have to clean the button top with a coarse pencil eraser from time to time when charging these cells.
I just did some testing with a 30Q, that I put a button top on like OP suggested.
First I charged the 30Q, after it was full I waited 1 hour and measured it and got 2352 mAh out of it.
For the second test I took the button top off, recharged it, waited 1 hour and after measuring got 2650 mAh from it.
As a third test I took the button top and sanded the flat part on some sanding paper.
I recharged the 30Q waited an hour put that button top on it and measured it and got 2632 mAh.
So with button top it only lost 18mAh.
Have to say that the 30Q was one year old and always fully charged.
Hence why it only got to 2650mAh
I used the same methode OP used on 50 other 18650’s and had no problems.
I do put 3 tiny dots of crazy glue on the outer ring of the button top before I put the paper sticker on it and let that dry.
Then I press it firmly on the flat top and use some heatshrink.
I do this so that the buttontop doesn’t shift when pressing the 18650 in a powerbank that was designed for a flattop.
You can use a drop of solder instead of a buttontop but with the way OP suggested, you can always bring it back to a flattop without damage.
Edit: If you want to do it right you need these the inner diameter of the ones above is to wide.
While we are at it this and get some of these
In my test i wasn’t speaking for capacity , but i said it didn’t allow a lot of current to pass , probably they are making poor contact (without being spot welded) . If you have a light with a fet driver and a clamp meter check it please (flat top vs added button top) .
Just curious why the big dragons leave this area fully to third parties (if I understand it correctly), is there not clearly a market for this? maybe someone knows?
Most (all?) manufacturers don’t want us hobbyists playing with lithium ion. If I’m not mistaken, Sony doesn’t even acknowledge they manufacture these cells. The cells are supposed to be used in battery packs, hence don’t have button tops.
