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  1. BlueSwordM

    Which Budget Spot Welder Should I Buy for a Few Battery Packs?

    The Kekk K7 Pro uses a really high quality PCB, with 9x MOSFETs, a nice TVS diode and best of all, a high quality firmware I actually received a Kekk K7 Pro PCB recently to replace the old one I had, and its capabilities are sooo much better it's insane. I can weld 0.1mm copper no problem with...
  2. BlueSwordM

    Thread for new battery breakthrough PR releases

    LMFP, our savior. I hope we'll get more than 190Wh/kg out of cylindrical LMFP cells since they're currently at this level, unlike prismatic ones which are at 220Wh/kg.
  3. BlueSwordM

    Thread for new battery breakthrough PR releases

    That only works for old papers since they stopped hosting new papers being sent by people.
  4. BlueSwordM

    Which Budget Spot Welder Should I Buy for a Few Battery Packs?

    As always, I recommend supercap welders. Here's the best ''budget'' one: https://www.aliexpress.com/item/1005007101175633.html
  5. BlueSwordM

    Thread for new battery breakthrough PR releases

    It's always funny seing 800 cycles at 80% DOD. That likely entails 250-300 cycles at 100% DOD. They're likely having difficulties dealing with homogeneity in cylindrical cells since tabbed cells tend to be problematic in this regard if your cell isn't tough enough, like a Molicel P50B.
  6. BlueSwordM

    Cycle life tests of High Energy density cylindrical cells

    Yes: 2500pcs at 2.95$USD each.
  7. BlueSwordM

    Hi all, I am having the same type of problem in my assembled ebike with 14s5p 21700 battery pack. After installing a smart BMS, i found out the reason

    Oh yeah, you should have mixed cells because this can easily cause one set of cells to become unbalanced vs the other ones. When dealing with used cells, I really recommend getting an IR meter to check how the cells patch as IR is a decent way of gouging cell health.
  8. BlueSwordM

    Cycle life tests of High Energy density cylindrical cells

    No sadly. I've been chatting with distributors, and they're NOW ending pre-production, so supply is low and difficult to get. The BAK 58E, on the other hand, is actually available to purchase in bulk at actually reasonable prices.
  9. BlueSwordM

    Thread for new battery breakthrough PR releases

    While we wait for the email, here's a paper detailing only the coating: https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/aenm.202102618
  10. BlueSwordM

    "Copper/nickel sandwich" buses for series connections

    On the topic of steel, if you peeps can get access to stainless steel strips in place of nickel plated steel, you should try it out. Stainless steel has even worse electrical conductivity than normal steel, which should help with our method of copper-sandwhich welding. Honestly though, our...
  11. BlueSwordM

    "Copper/nickel sandwich" buses for series connections

    Man, I do so much electrochemical research, and I even didn't of galvanic corrosion on most casing materials :P
  12. BlueSwordM

    Cycle life tests of High Energy density cylindrical cells

    High Si anodes tend to cause that.
  13. BlueSwordM

    Thread for new battery breakthrough PR releases

    Sadly, no. This publisher is a LOT more aggressive than the other ones when it comes to posting PDFs or links. I've already had to remove a link from another place for this reason. Just because you asked though, I will email the article writers; it usually works rather well to get a nice PDF...
  14. BlueSwordM

    Thread for new battery breakthrough PR releases

    For anyone interested, here's a related paper that I finally managed to get a copy of: https://www.cell.com/joule/abstract/S2542-4351(25)00062-5 They used a high power laser to massively increase surface area (also improving electrolyte wetting, but that's another topic) on the graphite anode...
  15. BlueSwordM

    Cycle life tests of High Power density cylindrical cells

    In before they increased the peak charge rating on the 45Ds lmao.
  16. BlueSwordM

    2025 best spot welder for DIY project ?

    Something like the Kekk K7 Pro would likely be a good choice for you: https://www.aliexpress.com/item/1005007101175633.html Otherwise, something slightly lower end like this new unit from Kekk also works: https://www.aliexpress.com/item/1005008107430366.html The firmware is not as flexible...
  17. BlueSwordM

    2025 best spot welder for DIY project ?

    What's your budget?
  18. BlueSwordM

    "Copper/nickel sandwich" buses for series connections

    Everything you wrote earlier was correct based on further researches, except for the part about zinc. There seems to be no other reason outside of maybe work hardening and perhaps zinc fumes during welding. However, I forgot one aspect: corrosion. Nickel is significantly less chemically...
  19. BlueSwordM

    "Copper/nickel sandwich" buses for series connections

    Your explanation is somewhat correct, but nothing else seems to explain why nobody uses brass in pack builds. However, zinc being vaporized during the welding process is reasonable since zinc oxide fumes do get generated when brass melts at a temperature of around 400C vs 900-1200C for other...
  20. BlueSwordM

    "Copper/nickel sandwich" buses for series connections

    The answer seems to be that zinc will get vaporized during the spot welding process, making the piece weaker. Furtheremore, it'll get temperature hardened during that process, making it significantly less flexible and easier to snap. In summary, just use 0.1mm copper + 0.1-0.2mm stainless...
  21. BlueSwordM

    "Copper/nickel sandwich" buses for series connections

    So, is there anything preventing us from using brass strips in place of nickel? It has slightly higher conductivity than nickel, similar thermal conductivity and yet, it is dirt cheap. All of these characteristics do seem to make a prime replacement material in place of nickel. Why haven't I...
  22. BlueSwordM

    A handy passive to active battery cooling blog post?

    The answer to the 1st question is that Neptronix either draws less power than rated, or they pick higher power density cells. As for electric cars, almost all of the modern ones have any form of active cooling; most of them integrate liquid cooling to properly thermally manage their packs...
  23. BlueSwordM

    What’s the best lifepo4 AVAILABLE?

    For cylindrical cells, what you can easily get are 40135 20Ah cells from the likes of EVE (EVE C40) at about 180-185Wh/kg: https://www.nkon.nl/en/eve-c40-40135-20ah-3-2v.html There also exists a nice 165Wh/kg 18650 cell, but I'd advise against building with 18650 cells today for practical...
  24. BlueSwordM

    A handy passive to active battery cooling blog post?

    I'd argue most ebike packs are just built to a lower standard than leading edge phones and most electric cars, particularly when it comes to cooling and charging algos. However, designs can still be pretty good: putting a good thermal pad below the cells inside of a metal casing can help a lot.
  25. BlueSwordM

    DDOSed by alibaba cloud

    Oh yeah, technical forums are absolute goldmines for datasets, particularly if you format them really well. The Qwen team should honestly calm down with the intense polling rate of their scrapers.
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