From: bill.sloman@ieee.org   
      
   On 20/12/2025 10:02 pm, Liz Tuddenham wrote:   
   > Bill Sloman  wrote:   
   >   
   >> On 19/12/2025 6:49 am, Liz Tuddenham wrote:   
   >   
   > [...]   
   >>> 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.   
   >   
   > Let's do some sums:   
      
   First show where you got your numbers from.   
      
   I've snipped out that bit of bizarre speculation.   
      
   In reality, the problem is picking up the increased rate of   
   self-discharge long before you get to the point where thermal runaway is   
   likely - the battery has to get above 120C before this can get going.   
      
   > The battery capacity of cars, on average, is about 70 kWh.  This means a   
   > resistor capable of dissipating 70 kW continuously is needed to   
   > discharge the battery in one hour.   
      
   You'd dump the excess energy slowly into the motor, letting it rock the   
   car rapidly back and forth by about a foot or so to generate a little   
   extra air circulation. It would take a while to discharge the battery,   
   but it would get it done.   
      
   It would be a emergency solution - the driver would get told that the   
   battery needed attention long before this would be justifiable, and in   
   our brave new world the battery condition monitor would probably have   
   it's own mobile phone to rat out the inattentive owner to the local fire   
   service.   
      
   > I'm sure cars with a red-hot bedstead of resistance wire on the roof   
   > would soon catch on.   
      
   Your enthusiasm for impractical solutions is noted.   
      
   --   
   Bill Sloman, Sydney   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)