#qi-hardware IRC log for Saturday, 2015-09-26

--- Sat Sep 26 201500:00
arossdotme-planbi seam to have over discharged my laptop battery after leaving suspended for a day or 2 until it ran out of power. trisquel (ubuntu lts but with linux 4.* installed instead via a repo) looking at the /sys/class/power_supply/BAT0/ info. voltage file num is less than the num in voltage_min_design . i fear this means its been over discharged and so might not be able to charge?01:08
arossdotme-planbstatus says its charging though01:08
DocScrutinizer05strange02:13
DocScrutinizer05but yeah, suspend-to-ram is a mode pretty much designed to kill battery on most laptops02:14
DocScrutinizer05I killed my ASUS OLPC(?) battery after only 2 months and ~3 charge cycles, with leaving it in suspend2ram02:15
arossdotme-planbasus netbook you mean?02:19
arossdotme-planbdam, i really hope i havnt02:19
arossdotme-planbwell i have one pack left which is my bigger one at least02:19
arossdotme-planbi would have thought a hardware batt protection would have kicked in?02:20
arossdotme-planbwell maybe/i guess i just have to acceptance the truth02:21
DocScrutinizer05you'd think there *must* be a hw protection against deep discharge. seems it doesn't always work or even exist02:27
DocScrutinizer05when the cells in battery pack are not properly balanced (both in production for properies and during battery management for discharge) I can see how discharging the pack can result in one cell getting deep discharged while the others till provide sufficient voltage so complete battery pack in within specks02:29
DocScrutinizer05~6*3.002:30
infobot1802:30
DocScrutinizer055*4.002:30
DocScrutinizer05~5*4.002:30
infobot2002:30
DocScrutinizer05see what I meant?02:30
DocScrutinizer05while a cheap battery protection might kick in at 18 volt, already at 20V one of the cells might see reverse charging which for sure kills it02:31
arossdotme-planbarr ok02:45
arossdotme-planbwould that mean one of the cells has become a ticking time one in that example you gave? the reversed charging/too low one02:46
arossdotme-planbticking time bomb02:46
arossdotme-planbfire hazard, etc02:46
DocScrutinizer05possible, yes03:34
DocScrutinizer05though batteries usually explode only when you try to charge such dead cell03:34
DocScrutinizer05and even then it's a rather rarely seen problem03:35
DocScrutinizer05violent venting and heat however may happen03:36
DocScrutinizer05real bombs only happen when some 'smartass' thought it's a nice idea to put a number of 18650s into a sealed waterproof housing made of airplane alu03:37
DocScrutinizer05http://www.candlepowerforums.com/vb/showthread.php?262234-TK-Monster-Explosion03:37
DocScrutinizer05>>I inspected the 8 green 18650 batteries that came with the light to check what kind of charge they were in. 4 of the batteries were at 100% and the other 4 had no charge. I charged the 4 batteries and came back to them shortly after to find them charged already. I carefully placed the batteries back into the light observing the polarity. <<  exactly the "unbalanced" case mentioned above that you *mist* avoid by all means. Also 03:40
DocScrutinizer05charging dead batteries here, then giving them massive discharge in a pack mixed with good cells03:40
DocScrutinizer05>>and came back to them shortly after to find them charged already<< should have made that dude wonder 03:41
DocScrutinizer05defect or dead or even fake 18650, charge them for a short while, then expect "well, everything OK and easypeasy, no?"03:43
DocScrutinizer05then operate a 100W(?) flashlight from them03:43
DocScrutinizer05yeah, when cells vent in a sealed alu tube, that's pretty much what you call a pipe bomb03:44
DocScrutinizer05(100W?) 250 actually04:52
arossdotme-planbhuh thanks for telling the story10:57
arossdotme-planbknow of anyway to get cheep but good li-* 12v+ 12AH min packs from?10:58
--- Sun Sep 27 201500:00

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