From: blockedofcourse@foo.invalid   
      
   On 12/6/2025 2:27 PM, legg wrote:   
   > Rechargeable 1.5V lithium batteries are complicated animals.   
   > Not a battery, as such, so don't rely on standard battery   
   > chemistry descriptions to cover them.   
   >   
   >  From tested behaviour:   
   >   
   > There's a real 3.7V lithium cell inside there somewhere, with   
   > a charging voltage of over 4V on the battery terminals.Open   
   > circuit when charge is terminated internally.   
   >   
   > When it's not being charged, a switching regulator takes over   
   > to produce 1.5V on the same terminals, drawing from the   
   > lithium cell. This buck regulator is unstable when the battery   
   > is not being used, so the battery terminal voltage jumps around   
   > if you try to simply measure it.   
   >   
   > I wonder what this does to devices that count on the low noise   
   > usually produced by simpler standard cells. Guess I'll find out   
   > the hard way. Loaded, the voltage will stabilize, but then you've   
   > got normal switching ripple and, supposedly, emc issues.   
      
   What about devices that count on the internal series resistance to limit   
   the current delivered to the load?   
      
   I.e., does the lithium capacity JUST change the total amount of   
   available charge?  Or, is it exploited to also change the VI   
   characteristics of the source?   
      
   > Nothing in the literature (?)- it's still the wild west as far as   
   > battery products go, in the far east. Currently less than   
   > US$1.50 per in low volume retail.   
   >   
   > I lucked into a bunch of rechargeable 9V (PP3) lithiums the other   
   > day - furnished with a micro-usb port for charging. Same basic   
   > idea, but with a boost regulator supplying the terminal voltage.   
      
   What sort of usage patterns are you trying to address?  I think the   
   only items, here, with 9V batteries are smoke detectors (and they   
   are mains wired so the battery is an afterthought).   
      
   Consumer "batteries" all seem to be headed to AAA and AA (with a few   
   AAAA just to screw things up).   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)