Youtube.com will make you a genius or a smoking idiot! Move forward with caution and remember all shortcuts lead to the Emergency Room.
A good Google page for Arc flash! https://www.google.com/search?q=arc+flash&tbm=isch&source=iu&pf=m&ictx=1&tbs=simg:CAES0QEJ24TjFZ8ovAYaxQELEKjU2AQaAggKDAsQsIynCBpiCmAIAxIo0ArcCtoKwBfNCsoXzwqZFckKxQvRItIqyCrJKtIi0Sq4KtMi2SKDKRowVq3_1QrChqjwNPjcgJ6cenC51ab4CWMgggm_1rHeOxKzGMcsFocJfte22orPb2sbuWIAQMCxCOrv4IGgoKCAgBEgRBrt0ADAsQne3BCRozChcKBWZsb29y2qWI9gMKCggvbS8wbDdfOAoYCgRpcm9u2qWI9gMMCgovbS8wMjVydzE5DA&fir=wExvN668YVFhlM%253A%252CoO20Qa16SBrwzM%252C_&usg=__yYOeGJ1ykoGS6agy8mCq9iMrY90%3D&sa=X&ved=0ahUKEwifnZnR6NnWAhUQzWMKHfN3ANQQ9QEIPTAD#imgrc=wExvN668YVFhlM: --Dave Dave Starlight Solar Power SystemsDave > Hi Drake, > > What chemistry of li-ion batteries are you talking about? Some, like > LiFePO4, are far less prone to thermal runaway as they have superior > thermal characteristics. Other chemistries should be avoided unless you > have significant cell level monitoring and control. > > As with all batteries, when any one cell in series with other cells > becomes fully intercalated (think of a lead acid cell in saturation), that > cell voltage will rise above the others that are still absorbing current. > With lead batteries this means off gassing and heat buildup of that cell. > With Li-ion cells, especially at high charge rates, this can produce a > fast temperature buildup. Some Li cells have pressure valves built in, > much like valve regulated lead batteries do. High temperature will cause > pressure from boiling the electrolyte. The vent opens to release pressure > and lower the internal temperature, hopefully. This stopgap greatly > improves safety but may not be sufficient to prevent thermal runaway. > > If all cells are matched for capacity and balanced, a good practice is to > under charge them. There is no reason ever to fully charge a lithium > battery and stopping short is a good practice for any Li chemistry. But > this alone is not enough. If you want to be more safe, monitor each cell > voltage AND temperature and turn off charging before any 1 cell exceeds > the specification for that battery type. This is done with a BMS. Our > systems all have BMS controls which I believe makes Li-ion batteries safer > than lead acid. In lead acid battery systems I have seen thermal run away > and several explosions. > > Beware: Notice above I said âmore safeâ. There are conditions that can > make a Li cell very dangerous, especially with a used battery, that you > canât tell from any non-destructive testing method. Study the formation > of dendrites. > > This subject is too vast to discuss in an email, so I recommend that you > study much before you proceed. Many others have been where you are now and > have paid a very high price for assumed understanding. > > Larry Crutcher > Starlight Solar Power Systems > (4+ years studying, designing and installing Li-ion energy storage > systems) > > > On Oct 5, 2017, at 6:45 AM, Drake <[email protected]> > wrote: > > Hello Wrenches, > > I've been contacted by a group who will be taking apart lithium ion > battery packs that have been retired, finding the bad cells and > recombining the remainder, then putting them in larger configurations for > use in PV systems and electric vehicles. > > How can thermal runaway be avoided? Is there any information that could be > of use in making these systems safe and effective? > > Thanks, > > Drake > > > > > > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > Dave Angelini Offgrid Solar "we go where powerlines don't" http://members.sti.net/offgridsolar/ e-mail [email protected] text 209 813 0060 _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
