I searched for Li-something for a recent project. They are *very* hard to= get hands on. Ultralife responded ultraslow, maybe will get the sample next ultra-life... Varta actually have visited me (after a half year =3D past deadline) and i= got a sample of a Li-polymer cell they will have in full production soon. IIRC Varta will have basically three sizes, one small for bluetooth thingys,= one medium for cell-phones, and one larger for small laptops/hefty handheld= computers. Li-polymer have the most energy per mass of all battery system i know of. Li-ion is slightly heavier and bigger, because it is not dry, and have= encapsulaiton. From all suppliers both types always comes with on-built protection against= over-and undercharge, as the cells may explode if used improperly. With this protection, and using advanced special charge-IC:s from i.e.= National Semicondoctor or Maxim, theese batteries are really performing= well and are really easy to use. Search their websites for more info on= algorithms, you might want to use a PIC, A/D, ref, PWM to make your own= charger. >Lithiums are not as robust as NiMH though=20 I would say both NiMh and Li-X are at least as robust nowadays, as NiCd. >-- you have to make sure never to >discharge them below 3V/cell the onbuilt protection takes care of that, and the chargers usually have a= soft recondition mode at undervoltages. For easiest start, I suggest buying a spare battery pack for a cell-phone,= and build a charger around a specialized Li charger IC. One last note: there are basically two charge types, one go to 4,1 V, th= eother to 4.2 Volts. 4.2 is the most usual, but you might want to check= the voltage at end of charge cycle on the relevant cellphone. /Morgan -- Morgan Olsson, Morgans Reglerteknik AB H=E4llek=E5s, 277 35 KIVIK, SWEDEN info@morgansreglerteknik.se http://www.morgansreglerteknik.se tel +46(0)414-446620 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.