I don’t think I ever said specifically what I measured with the original button tops still in place, I checked them out in my charger at least twice and got these results:
96, 80
56, 78
93, 99
This last one was worse and had the button top that came off the easiest. I did several checks.
125, 651, 135, 435, 41
So they weren’t as erratic as Mike’s results.
Dang so was my charger possessed or something? I had a hard time getting any of them below 300.
If you check them when full or nearly full, the IR readings will be less erratic, IME.
Ok Pete that makes sense kinda. Ive never checked that but i will tonight with some of my panasonic cells. Those bounce around a bit too.
I don’t really know. I did notice the bottom of the cells were a bit scratched up. I used a bit of scotchbrite to clean them.
I got them mailed today, so you might get them Tuesday and we can see what they read on your charger.
Ok thank you Jason. I’ll let you know when i get them what they read
If anyone is curious about the basic principles of spot welding on a battery, I found this random video on YouTube that shows a very simple homemade spot welding machine. It’s pretty neat.
More details of his setup.
Thanks for that spot welding video, it's very helpful.
Yeah, these techniques on lithium batteries look a bit sketchy to me.
I’m familiar with the automotive style spot welds. It’s typically with robots, but can also be done by hand. You pinch the two pieces of metal from opposite sides and apply hundreds of pounds of force squeezing them together and then the electric charge flows through. The metal basically liquefies and fuses together.
Maukka, how do you do your spot welds? A spot welding machine or something home made?
First time I've seen any spot welding on batteries. If I did it, I'd probably wear my motorcycle helmut just in case the batteries blow up in my face.
Why would you think that would happen? The current only flows across that tiny gap, not through the battery, there are no flammable fumes and the battery doesn’t get very hot.
In that first video, that first weld he does has a pretty good flame. I don't feel comfortable with a flame near a battery. My safety instincts kicking in, even if there is no chance of it happening.
I was looking at some entry-level spot welders on AliExpress that run on 110v (model 788H) and with shipping to the US, it’s around $175. The spot welds from it looks much weaker than the homemade setup in the video I posted. I would guess that it’s safer than the homemade one. The better spot welding machines are in the $1000 range.
I’m using a kWeld spot welding kit.
Videos from the guy behind it:
That looks really nice.
I am officially super confused with spot welding kit. Plus I can’t afford $1000 lol. I don’t weld though so I guess that’s ok. Interesting videos though.
Pretty sure this might be a bit off topic but i tried cleaning the ends of my Sofirn button top cell unprotected that a fellow BLF member suggested windex would work (anything non conductive) and i was getting 999,700,600,135,150 mohm etc… Readings. I used windex and some paper towel to clean or try cleaning the ends.
I rubbed with with off brand windex then dried it with dry paper towel…. Let it air dry for about an hour.
Did i do something wrong? I know Jason used a different method to clean the cells. I will tell you however that i have been using the Sofirn cell in the C8F on the higher modes as a bicycle light for around the trailer park at night. Maybe that has something to do with it also? When i put it in the charger i was getting highish readings of 134 up to 205 mohms…
Any suggestions would be much appreciated!
Thanks,
Mike
I keep this around because it’s handy.
Or
These are kind of like steel wool, but safer as they are made of synthetic fibers and are non conductive.
You want to remove the build up and/or contamination on the metal surface, without rubbing through the surface finish. I assume the ends of the cell are made of steel because a magnet will stick to it. Then they use some type of surface coating to protect from rusting.
I’ve never heard of using windex. Sounds kind of strange to me plus I would want any liquid on my cells. I’ve heard of people using a pencil eraser. I dont know if itcworks, though.
That steel wool kind of stuff you sent the links to I’m pretty sure I’ve used before. My step-dad is a carpenter and has loads of those things everywhere but they are all very dirty. I’ve tried the pencil eraser and it did work pretty well. I just figured I’d try the Windex to see how that worked but I’m not sure if I like that idea. I will have to buy some of those steel Wool things. Can i use that on the charger too? Or do i just need to worry about the cells?