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  1. 2Big2B

    Dead Cells

    Actually I have an idea for you. I am using a 8s 29.2v 100ah DYI pack to run my power wheelchair. I use a 10A LiFePo 28.8V Battery Charger designed for it. If you found one of those cheap you could charge yours in series. I bought one used on ebay for $20. OTH, you probably really should...
  2. 2Big2B

    Busbar help pls

    I am sure you are right. I was using this for a 8S 24v 100Ah battery pack I was building, and the copper flat bar was on hand. That is the only real reason I used it. That thick copper was a PITA to cut and drill, hence my idea to make cardboard/cardstock busbar templates to verify alignments...
  3. 2Big2B

    Drok DC 0-300V 200A questions since manual would make Ikea happy.

    I am just in the process of trying to figure out how to calibrate my Drok battery capacity meter for the 8S 24v 100Ah pack I have just installed on my Big Bounder power wheelchair that I use for recreation. It needs a fuel gauge, hence the Drok. Trying to read the pamphlet Chinglish instructions...
  4. 2Big2B

    A faster & better way to top balance?

    Seems a bit extreme - just to make rechargeable batteries for my electric wheelchair... Anyway, this thread seems to have gone all the way to Cuba and back. End of Hijack. :cool: Thanks guys.
  5. 2Big2B

    A faster & better way to top balance?

    Thank you.That's what I needed to know. That 208v 3 phase supply wouldn't work with the clothes dryer power outlet...
  6. 2Big2B

    A faster & better way to top balance?

    I am thinking I might be able to just plug it into the 3 pole socket for the clothes dryer. I can't find a picture or any docs about its plug though. Apologies for hijackings the thread... my thought was to bounce this off of Steve in context to the subject in hand ...
  7. 2Big2B

    A faster & better way to top balance?

    I have a 8S 29.2v 100A battery pack I just built with an Overkill 8S 29.2v 100A BMS. I bought a matching (AliExpress) 8S 29.2v 10A Wheelchair battery charger for it. I am also building a second pack just like it using 8 3.2v 100ah cells, ergo 8S 24v 100Ah. I will use a Daly 8S 24v 100Ah for...
  8. 2Big2B

    A faster & better way to top balance?

    That 30v 40 amp model costs $239.86. At about $20 each, assuming they are all the same make/model, if I wired 4 of them together and it worked I would end up with roughly the same thing for $80 ! (maybe even cheaper if seller accepts a lower offer for all 5...) That is what I am investigating...
  9. 2Big2B

    A faster & better way to top balance?

    Can I stack multiple power supplies in parallel to boost amperage? I have a 8S 29.2v 100A battery pack I just built with an Overkill 8S 29.2v 100A BMS. I bought a matching (AliExpress) 8S 29.2v 10A Wheelchair battery charger for it. I notice someone is selling some used "28.8V Battery...
  10. 2Big2B

    Overkill BMS defaults?

    I figured it out. It was a driver issue.
  11. 2Big2B

    Overkill BMS defaults?

    Not really. That's why I bought the UART USB box that is being so antisocial. I am still trying to wrap my head around how USB communicates to a comm port. I am old school and how USB talks to the system has always been a mystery in this regard. And my other mystery to solve is about...
  12. 2Big2B

    Overkill BMS defaults?

    Question: How reliable are the Overkill BMS pre programmed parameters? I just finished building my 8s 24v 100ah battery pack using the Overkill BMS for it. It appears to be working great. A Bluetooth module was included, but I don't use a smart phone or anything that I can run its program. I...
  13. 2Big2B

    Busbar help pls

    Take a look at my recent post about making up some cardboard bus bars so that you can tweak out your alignments. I also posted the method I used and source to make custom bus bars from readily available inexpensive copper flat bar stock using simple hand tools.
  14. 2Big2B

    DIY BUSBARS

    It's nice to have the right tools! I was able to make do with what I had. If I could have taken it somewhere to have it done inexpensively I would have. These days that probably will never happen though. So, a hand drill, hand jigsaw, a strong table, big clamp, a piece of scrap 2x4 and some...
  15. 2Big2B

    DIY BUSBARS

    I just made a couple of sets of copper busbars from solid flat mill Bus Bar Stock that I found on ebay for about $12 each per 14" long bar. That is long enough to carve out about 8 bus bars. Aluminum bar stock works too, but it only it has 61% conductivity compared to copper. (The bar stock I...
  16. 2Big2B

    Cardboard Busbars !!!

    In the process of cutting my own heavy copper busbars customized for a 8S 24v 100ah build I came up with a template for drilling and cutting them from flat bar copper. The real moment of truth is when you are about to install the bus bars in series after the parallel top balancing. This is when...
  17. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    I guess that is how this works - although it is rather subtle. Lead Acid batteries of course have a different profile, so the effect would be more dramatic. My thinking all along has been that each cell is a closed system. However, depending upon SoC, the connections at each common terminal...
  18. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Interesting. I guess I never really thought about it that way. So what I think you are saying is that in my way of thinking, to the left are two cells, like containers of fluid, self contained. A pipe, eg "rail" connects the (+) poles together on top and (-) poles at the bottom. In this case...
  19. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Hmmm... Ok, I'll bite. That certainly is not intuitive, but its an experiment that might be worthwhile. Maybe I will learn something. That's what I am here for. Thank you.
  20. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    "Let's put two of these cells, at different state of charge (and let's assume a noticeably different terminal voltage), in parallel with one another. This forms closed circuit (agreed?)" Huh? This is exactly where I am stuck. The implication is that by slapping a pair busbars across their...
  21. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Non-Sequitur. That is not what I am asking.
  22. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Again, Non-Sequitur. The only "connection" shared by the cells is the fact that their common poles are glued together. I think the problem is conceptual. I think what you are saying is that by doing that the entire bank becomes one big communal cell that somehow shares its chemistry. If that is...
  23. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Thank you. I appreciate your effort to explain it to me. However, everyone seems to be missing the point. I am being treated like a small child asking how immaculate conception works. You can carefully and politely explain how human reproduction works until you are blue in the face but I will...
  24. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Can we get Will to mediate?
  25. 2Big2B

    Paralleling LFP cells at rest to "balance" them

    I guess we have to agree to disagree. I can't understand where there is a handshake between the cells that way. Not unless there is some kind of leak. I don't drink. I have had this question all day. So, i am not drunk or on medication. I am just ignorant?
  26. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Thank you. I was wondering if I stutter. We share the same ignorance I guess. Yet it seems that a lot of people seem to believe it works that way and present it as truth. But, I guess I am just ignorant and shouldn't ask stupid questions. Meanwhile I have my string of 8 cells wired up in...
  27. 2Big2B

    Paralleling LFP cells at rest to "balance" them

    I am a licenced amatuer radio operator since about 1990 - Coded Technician class (callsign N2MZN). I am a retired computer engineer, Comptia A+ Certified. I am college educated. Big deal. But I surely know the basics and what is obvious. What intrigues me is whatever the principle is that...
  28. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    Thank you. That is my question exactly. I agree that voltage is a lousy way to measure and test such a phenomenon. The premise though, no matter what method is used to measure, is that if Cell A has a high SoC and Cell B has a low Soc, that by combining their poles in parallel will accommodate a...
  29. 2Big2B

    Paralleling LFP cells at rest to "balance" them

    The Sun rises in the east and sets in the west. Current flows from high voltage to low. What does that have to do with it? If two cells are placed in parallel with nothing else connected to them, what exactly accomodates the flow from high voltage to low between them? Osmosis?
  30. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    I am not talking about a BMS and how it passively balances. I am talking about the case of two cells, one fully charged (Cell A) , the other in a discharged state (Cell B). Assume both battery cells are healthy. Check voltages with an accurate VOM, like a Fluke meter. Then set them up in...
  31. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    To that post I have just replied as follows: I still don't get it. The suggestion here is that there will be some intercourse between the paralleled cells, but not very significantly. Why should there be any interaction between them if no charge or load is applied to the terminals? I might...
  32. 2Big2B

    Paralleling LFP cells at rest to "balance" them

    I still don't get it. The suggestion here is that there will be some intercourse between the paralleled cells, but not very significant. Why should there be any interaction between them if no charge or load is applied to the terminals? I might expect a slow degradation of SoC independently that...
  33. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    This is a couple of google results There are two basic approaches to balancing: Passive balancing drains charge from cells having too much charge and dissipates drained energy as heat. Active balancing moves charge from “high cells” to “low cells,” attempting to conserve energy in the battery...
  34. 2Big2B

    Passive Top Balancing ? How/Why does it work ?

    That I understand. But that doesn't address my question. Can battery cells set up in parallel, sitting idle without anything connecting to the main terminals (e.g. "Rail") balance into a common SoC. If so, by what process. I don't think so. I think some others do though. Please explain.
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