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  1. Overmind

    Heat evac: 26650 vs 21700

    Let's look a little at the 26650 vs 21700 situation regarding heat exchange / overheating. Let's assume the following: we have a 26650 and a 21700 made with identical chemistry and we want to charge/discharge them. Which one can evacuate heat better, which one will overheat faster on the same...
  2. Overmind

    Can this 4S BMS work in 3S mode ?

    Anyone recognizes this ? : Will it work in 3S mode ?
  3. Overmind

    My future 1st solar

    I will do a solar system at my folks country place and I'm currently on the research phase. Desired rating is 2.5-5KWh. I long-ago established that I will go with LiFePo4 cells of 100Ah, I have a good supplier for such "bricks". 16S of them will make 48V-equivalent. So far so good, this one is...
  4. Overmind

    Testing capacity of power tool batteries - any ideas ?

    I'm thinking into doing something to be able to test the capacity of power tool batteries like Milwaukee, DeWalt, Makita, etc. Given that the modern batteries auto-lock when reaching minimal power level I only need to find a way drain them in order o measure capacity. Are there any special...
  5. Overmind

    LiFePo4 "Bricks" actual lifetime

    Din anyone used LiFePo4 batteries like the ones below ?
  6. Overmind

    Should there be a new section ?

    Since some publish very professional reviews of various cells that they tested, I was wondering if it could be a good idea to make a new section just for reviews and new cells testing. What you you think ?
  7. Overmind

    M365 - what type of cells ?

    Does anyone know what type/brand of 18650 cells do the e-scootersXiaomi MI M365 and the Pro version use ?
  8. Overmind

    Suppliers of 20Q / R / RM ?

    Someone is looking to replace some Samsung 20Qs inMissouri. Is there any shop/supplier there or around where he could order some Q R or R/Ms ?
  9. Overmind

    UPS and LiFePo4s

    Did anyone test if generally a series of 4 LiFePo4s can be compatible with standard UPS units that use lead acid batteries ? It could be really useful... If anyone tried this please share some feedback.
  10. Overmind

    Production costs 2020

    I'm trying to estimate production costs for li-ion batteries 2019-2020. I found some older info from 2009, which is clearly out of date: See page 18 And some stuff from 2016here. Anyone have some updated info on $/kWh manufacturing costs ?
  11. Overmind

    High current tester modding

    Did anyone attempt to mod a tester like the Lii500 or Opus or anything like that to make it support higher discharge test current, like 2A or even more ? Most of the chargers on the market only test on all slots at 0.5A; Opus needs extra cooling for 1A across all slots. It would be nice to be...
  12. Overmind

    3 months error

    I was trying to RE on an older topic and I get an error saying something about being older than 3 months. What's up with that ? There is no reason to open another topic about the same cell.
  13. Overmind

    Powering with 4.8V

    I encountered a problem from someone: he wants to use li-ion cells to power a small motor that works at 4.8V. Problem is that a single cell would be too low and 2 in series would be too high. I'm thinking of recommending him using 2 cells in series andsomething like this...
  14. Overmind

    Interesting TR article

    I found this article interesting: I wonder what that LG battery is made of.
  15. Overmind

    EN-EL15 - what cells ?

    What kind of cells doEN-EL15 batteries used in DSLRs have ? From the size, I'd guess there are 2 18550 in there, but from the stated capacity, 2 18350s would fit the description.
  16. Overmind

    Motor exact specs

    Does anyone know what current draw does the RS540 motor have (powered at 7.2V / aka 2 18650 cells in series)? Link here [/URL]
  17. Overmind

    Anyone ever used 38120 ?

    Anyone ever used 38120 cells ? Their specs are LiFePo43.2V 8-10Ah. Pretty good capacity. I definitely can think of some applications for them but I never tested something like that. I'd be interested in how well they maintain capacity over time and if they could be an alternate solution for...
  18. Overmind

    12 slot charger with under $15 cost

    Since at a point I needed to charge a very large amount of batteries and the chargers I had were insufficient (a 6-slot and an 8-slot), I thought to build one of my own, out of scrap materials...and with more slots. The only things that I did buy were the Li-ion single cellcircuits, that's...
  19. Overmind

    Cells measured after over 5 years of storage

    I am attaching a table with the results of recent capacity testing of a few hundred recycled cells that have been stored at full capacity for 5+ years and recharged about 1 time per year. Notes: The colors represent the cell color. Similar for the cap color (the 'O'). The 3-letter...
  20. Overmind

    Hail all

    Hello, I'm an IT expert but I like tobuild various stuff for fun and science (lasers, flashlights, variouselectronic devices - I use lasers on science projects a lot). I prefer powering-up everything I do or use with 18650 cells, since they are easy to find and pretty cheap and can fit most...