Not just semi-OT, Rodrigo! Have you considered the possibility that the wierd component might be a FUSE? Proceed with caution. Dick ----- Original Message ----- From: Rodrigo Ventura <yoda(a)isr.ist.utl.pt> To: <classiccmp(a)classiccmp.org> Cc: Tony Duell <ard(a)p850ug1.demon.co.uk> Sent: Friday, September 01, 2000 6:11 PM Subject: Ni-MH pack topology [semi-OT, I know, sorry...] > > I was wondering whether anyone here could help me on this one: > I have a battery pack of a mobile phone I'd like to replace for a set > of AA Ni-Cad batteries (reason: cheaper!). The mobile phone even has > the necessary mechanical/electrical pieces necessary for the mobile to > work with 4 AA batteries. The question is a couple of extra small > terminals the pack provides. I dismantled the pack and I found out > that one of them was connected to the pack (-) terminal, and the other > one was connected to a weird component, which is connected to the (-) > terminal. My question is: *what* weird component is that? > > Some clues: It looks like a common 1N4148 diode: glass > capsule, two small copper-color cylinders, and something really small > in between. However, it is not a (common) diode! However, I suspected > it were a zenner pair (in series, symmetric polarity), and therefore I > tryed to measure the zenner voltage by connecting the component in > series with a 1K resistor, to a variable voltage power supply. In > fact, varying the voltage does not affect the voltage drop across the > component, remaining at 9.1V. At this time I was pretty sure it was a > zenner pair, maybe for protection or something like that. > > However, the mobile does not charge the batteries (and does > not recognize their presence) if this component is removed! The mobile > charger has about 7V (open circuit), so I was expecting the supposedly > zenner pair to be "open". What I did was to measure the extra pin > voltage: without the component it measures about 2.5V, *with* the > component it drops to about 1.2V. So the component cannot be a zenner > pair. And this was the time I had the idea to post this message... > > Thanks for any help/clues/(flames?) given! > > Cheers, > > > -- > > *** Rodrigo Martins de Matos Ventura <yoda(a)isr.ist.utl.pt> > *** Web page: http://www.isr.ist.utl.pt/~yoda > *** Teaching Assistant and PhD Student at ISR: > *** Instituto de Sistemas e Robotica, Polo de Lisboa > *** Instituto Superior Tecnico, Lisboa, PORTUGAL > *** PGP fingerprint = 0119 AD13 9EEE 264A 3F10 31D3 89B3 C6C4 60C6