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Stanford Develops 'Safe' Battery

1/18/2016 03:30 PM EST
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green_is_now
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Re: oh thats great, but....
green_is_now   1/23/2016 1:10:28 PM
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@ Jessica

Output short circuits.

it has the same function as a resettable switch, but tied to electrode temperature.

This can have value for series connections of cells, buried electrodes in a battery stack will have the same steady state temperature as the cells themselves, at least all the inner electrodes that have a cell on the left and the right.

It can be the P&J inside the sandwitch with a small, probably neglible for safety conserns time constant to internal cell if above Sandwich in stackup.

This idea and the original one have a basic issue of competing expansions if this is not mechanicaly solvable. Expansion of cell impiges on electode thermal switch that needs room to expand.

You have to insure the electrode thermal switch can win in an expansion fight.

green_is_now
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Correct this only shuts off external current flow, unless they make a membrane battery
green_is_now   1/23/2016 12:26:05 PM
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@ Elisabeth,

...and the other issue with this electrode thermal switch or it being moved in a membrane battery (or both) is its cycle limit.

If its safety claim is tied to only a # of cycles less than expected in service then this is problematic claim.

David Ashton
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Re: Temp Sensor
David Ashton   1/20/2016 3:07:10 PM
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@Elizabeth....true.... Li-Ion cells can overheat internally very quickly, not like the old NiCds and NiMHs....  :-(

elizabethsimon
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Re: Temp Sensor
elizabethsimon   1/20/2016 2:43:09 PM
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Unfortunately, that only works for problems OUTSIDE the battery cells. The battery can still overheat/explode for an internal short.

I would hope that battery manufacturers are at least using thermal cutout switches between cells in their packs.

Years ago, I was on a project where we used a litihium primary (non-rechargable) battery. After some experiments with exploding batteries, we ended up using Duracell 6V (two cell) camera batteries which had a thermal cutout between the cells

 

David Ashton
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Re: Temp Sensor
David Ashton   1/19/2016 6:56:28 PM
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@Kevin...or you could use a good old low-tech bimetal thermal cutout switch :-)

David Ashton
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Re: oh thats great, but....
David Ashton   1/19/2016 3:12:44 PM
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Jessica....Laptops are the obvious one, not a heavy draw like cars, but there have been instances of them catching fire. Then again, you'd be pretty p...'d off if your laptop just shut down without saving your 20-page document!   Phones and other small things usually have very small batteries, but might be applicable here.  Then there are all the horror stories about Chinese-designed goodies catching fire.  It would be a good safety net for bad design!  It will be interesting to see what the developers say about this.  The current capacity will have a big impact on its applicability.

DCH0
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What about separator failures?
DCH0   1/19/2016 2:31:40 PM
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The fires generally start with a failure of the separator as famously shown by the SONY laptop and Boeing Dreamliner incidents.  This seems to act as a fuse for the battery discharge to an external load but would not protect against internal failures.

Jessica Lipsky
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Re: oh thats great, but....
Jessica Lipsky   1/19/2016 2:28:16 PM
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I'm waiting to hear back about that one - do you have thoughts on where a battery like this could be most useful?

Kevin Neilson
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Temp Sensor
Kevin Neilson   1/19/2016 2:18:23 PM
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Am I missing someting?  Why can't you just shut off the load if the temperature (based on a thermocouple) gets too high? 

MWagner_MA
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Still worth it even without high discharge rates...
MWagner_MA   1/19/2016 7:22:40 AM
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Taking a quick peek at \batteryuniversity.com the energy density of LiPo's are comparable to the best NiMH which don't have the problem(fire).  However, LiPos are superior when it comes to self discharge rate.  So if a product isn't used very often or charged, this is a significant factor, and now it can be as safe as NiMH.

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