I appreciate the feedback. I have put in a
request for more information to the project
organizer to see what methods he is planning to
use, and what type of battery is to be recycled.
The dangers expressed are pretty alarming. If I
am to be involved in this project, solid planning
and safety precautions need to be implemented.
I'm also concerned that if some of the cells are
bad to begin with, maybe many more will be
heading for failure as well. It would seem that
the system would need to be very modular, with
clear indications of cells that would need to be changed.
Thanks,
Drake
At 03:44 PM 10/5/2017, you wrote:
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 <[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
>
>
>
>
>
>
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Dave Angelini Offgrid Solar
"we go where powerlines don't"
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e-mail [email protected]
text 209 813 0060
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