From: bill.sloman@ieee.org   
      
   On 19/12/2025 6:49 am, Liz Tuddenham wrote:   
   > Bill Sloman  wrote:   
   >   
   >   
   > [Lithium batteries    ....again!!]   
   >   
   >> More technically, they can go into thermal runaway - they have to get   
   >> above 120C before they can do it,   
   >   
   > How does the sensor monitor every part of the battery?  A small defect   
   > in a separator could easily heat up to 120C before the temperature of   
   > the mass of the cell rose noticeably.   
      
   A single temperature sensor in the middle of battery monitors for   
   increased heat generation in every part of the battery. The components   
   have a much higher thermal conductivity than the outside air.   
      
   I've argued for a tetrahedral distribution of sensors around the central   
   core. They could detect an area of localised heating. the idea didn't go   
   down well.   
      
   >> so any sensible battery condition   
   >> monitoring scheme can warn the user long before there much of a risk.   
   >   
   > Warning the user isn't much good, the battery technology needs to be   
   > fail-safe not impending-fail-evident to the user.   
      
   Fail safe would involve a big resistor into which you could start   
   discharging the battery if you detected worrying warming. You'd have to   
   design the system to cope with that, and it would  make the designers   
   job more difficult.   
      
   Bad designers make their lives easier by ignoring that kind of idea.   
      
   --   
   Bill Sloman, Sydney   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)