From: dp@tgi-sci.com   
      
   On 12/6/2025 23:27, 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.   
   >   
   > 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.   
   >   
   > RL   
      
   I have some AA and AAA ones and have measured them unloaded   
   (well, apart from the 10M of the multimeter) and they were OK,   
   I mean no noticeable up/down on the readout, have not looked   
   at them with the scope.   
   Just got them on aliexpress, no brand I can remember.   
   I have two AAA in an IR thermometer which must have very low   
   consumption while "off", nothing of interest has happened in   
   well over a year.   
   I managed to damage one of the two AA in my torch, the latter   
   will sometimes not go on with the button and needs a strongish hit   
   with a palm.   
   I opened it, the wire from the PCB and the battery button was   
   torn (probably my deed though it must have been waiting for the hit   
   to get disconnected). Fixed it and it now works again inside   
   that torch...   
      
   ======================================================   
   Dimiter Popoff, TGI             http://www.tgi-sci.com   
   ======================================================   
   http://www.flickr.com/photos/didi_tgi/   
      
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