[RE-wrenches] Second Life Batteries

[Drake]

Those are great arc-flash photos. Are we really 
getting into a serious risk of this sort of 
situation with a Li-ion battery? What really 
happens in a worst-case-scenario situation with 
them? How many people have blown themselves up to date? :-)

Thanks,

Drake

At 01:16 PM 10/5/2017, you wrote:

>  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 “more safe”. There are conditions that can
> > make a Li cell very dangerous, especially with a used battery, that you
> > can’t 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 <drake.chamberlin at redwoodalliance.org>
> > 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
> >
> >
> >
> >
> >
> >
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>
>Dave Angelini Offgrid Solar
>"we go where powerlines don't"
>http://members.sti.net/offgridsolar/
>e-mail  offgridsolar at sti.net
>text 209 813 0060
>
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