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 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 <drake.chamber...@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 offgridso...@sti.net
text 209 813 0060
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