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  1. P

    A123 20Ah Pressure Thoughts--and bits for experiments.

    One-time digression.. U know, that company claims 3.357V to 100% SOC and charging current =<3.650V. Others say LFPs accommodates past 4V bursts w/o issues. Guess I'll never really know. Maybe it's a different chemistry but I've got a feeling all LFPs are nearly identical.. :?:
  2. P

    BMS Distrust for Valued LFPs

    Hey, thanks!!! Will seriously consider that. :)
  3. P

    BMS Distrust for Valued LFPs

    Yes...I should get a basic BMS.
  4. P

    BMS Distrust for Valued LFPs

    Hi all, My distaste for BMSes has ended. Looking for an affordable one (from China, not much of a choice). Need advice. 1st timer...help!! :oops: I've newly acquired 36 x 74Ah LFP cells for a 32s1p arrangement. 4 spares. E-motorbike DIY. Battery + BMS selection stage. All cells are in the...
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    LFP Cell Selection based on Self-discharge Voltages

    Thanks, dnmun.
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    LFP Cell Selection based on Self-discharge Voltages

    By the way, what wire gauge would anyone recommend for an 135kg e-bike, 40A (estimated average), occasionally bursting to 140A for <30s..? The hub motor's phase wires are 7ga (2ft total). I was thinking 9ga for cells in series (3ft total) and 8ga (1ft total) for cells<--->controller..? The...
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    LFP Cell Selection based on Self-discharge Voltages

    Sorry, forgot charging details. Charger: 113VDC, 6A. Voltmeters are +0.03xV (So 3.34 = 3.31V). Near 10mA each. The 3.34V base was after a test charge for about 30 seconds. The actual OCV was 3.286V(multi-meter)-- all 32 cells. They had been balanced in parallel for 48hrs. Bulk charging was...
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    LFP Cell Selection based on Self-discharge Voltages

    Thanks!! New Topic: How does one ensure a PRC made BMS is reliable and won't ruin the whole ($7000) set? e.g. Smoked MOSFET, Wrong ga, 2nd-hand parts, inauthentic parts...never-ending, darn. This is the ONLY 2.5-3.65V, 32s, 140 - 150A, BMS 'reseller' whom I can access to, that is affordable...
  9. P

    LFP Cell Selection based on Self-discharge Voltages

    On it, pal...I'll try doing it 6-hrly...thanks!!
  10. P

    LFP Cell Selection based on Self-discharge Voltages

    Cell 27 does not. It self-discharges more than 5 times the rate relative to the other 35. And I trust my stringent test conditions. This might not correspond to what guru-member 'liveforphysics' earlier elucidated: Now, if one engineer says a 15-mile suspension bridge will buckle and another...
  11. P

    Smoked BMS....

    Hi wb9k, Thanks a bunch! :)
  12. P

    LFP Cell Selection based on Self-discharge Voltages

    Hi... 15-day test done. You think 35 cells are ok for a 32s selection? And wld 30-day be better? Thanks! Ok...I'll figure out how when assembled. The mV on cell 27 is suspect and CALB may send me a replacement. I love the cells...darn difficult to get them in and are supposed to be premium...
  13. P

    Bottom balancing?

    Yes, THANK YOU...I hope you would still.
  14. P

    Bottom balancing?

    Can't seem to log CELL DRIFT data as yet nor do I know how to. Perhaps someone can illuminate. I do not want a BMS due to the lack of space and trust for reliability...those small parts; Lack of time to test several (e-bike/motorbike-sized) BMSes, then settle for a trusted vendor...at least in...
  15. P

    Smoked BMS....

    The attached was bought from some Chinese company (details on last page of .pdf), assembled by another independent Chinese battery pack assembly technician (who called them for assembly instructions 14 months ago) ; he had never installed that kind of BMS before, just many of the simpler...
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    Smoked BMS....

  17. P

    LFP Cell Selection based on Self-discharge Voltages

    Thanks. Time to conduct a fair self-discharge test then....but perhaps just a 2-week test at the same temp / environment / etc.. Hopefully they discharged to 30% SOC before shipment and the initial 3.297 - 3.300V 9 weeks back wasn't @ 30%. Sounds more like 50% to me when they were determining OCV.
  18. P

    Bottom balancing?

    Amberwolf, best stuff! Thanks. :)
  19. P

    Bottom balancing?

    You did mention about not throwing away money by using a compact yet reliable $60 BMS (then blotted it out). I do not mind trying...u have a link? Thanks.
  20. P

    LFP Cell Selection based on Self-discharge Voltages

    Good stuff... But the cells logged by the factory line 47 days ago seem very identical... The IC told me that out of 100k+ cells, this is the most similar group he's ever sold (because I requested for that)... Now maybe I had requested wrongly and should have asked for dissimilar ones..(a...
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    Bottom balancing?

    Ok, erm...I don't intend to use that bulky Canbus BMS on the new cells or pry open the old casing to meddle with the connections of a Canbus BMS I did not install...and could have been installed wrongly. This might offend you but in fact, I don't even intend to use a BMS on the new cells.
  22. P

    Bottom balancing?

    Based on subjective observations when charging at near 10A, most of the current goes into group 1 and little into group 2. The technician might not have spliced things correctly and the whole case is too bulky and cumbersome.
  23. P

    LFP Cell Selection based on Self-discharge Voltages

    Hmmm...I see. Thanks. Therefore, 1 cell self-discharging about 55% quicker than the other 35 tells nothing about the overall health/state of that cell, when compared with the rest...? Also, they were sent at 30% SOC...and they estimated 3% SOC self-discharge/mth. So they could be about 25% SOC...
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    LFP Cell Selection based on Self-discharge Voltages

    Hi All, Need your well-informed opinions. The attached.xls shows 2 OCVs for 36 cells within a 47-day self discharge time lapse. I'm trying to pick the best/most similar 32 out of 36 cells before parallel balancing. Please advice which 32. Series assembling would then follow. The .xls...
  25. P

    Bottom balancing?

    Hi dnmun and all, After 9 days of trying to balance the old CAM60Fls...I seriously give up. (At least several) slave 2's cells just do not rise...from the first....no matter how high slave 1's cells do....regardless of balancing mode or forced-charge mode to 109V. My attention now turns to...
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