Can I still be able to use BJT transistors here? I don't own a TL431 but luckily I can get one nearby. and if I start buying mosfets, then my bill will go up. Now what's confusing me is that three names are thrown at TL431. You (Nigel) calls it a "super zener", texas instruments calls it an "adjustable precision shunt regulator", and the local store calls it an adjustable voltage regulator.
If someone was able to make a battery charger with auto shut-off feature using a transistor connected to the LM317 regulator, couldn't I somehow pull something like that off as well?