On 07/10/2010 15:45, Sean Breheny wrote: > Hi Matt, > > Voltage is not arbitrary - it is determined by the cell chemistry. > .... > Zinc manganese dioxide (aka Alkaline batteries) are about 1.5V and Almost 1.6V down to 0.9V > Nickel Metal Hydride are about 1.2V. maybe a bit more than NiCd Perhaps nearly 1.3V full charge and down to about 1V There never ever was a "1.5V" battery, That's just a nominal Zinc Carbon=20 voltage, maybe the first dry cell from the 1890s. On 10 hour discharge, the 1.5V quickly drops to 1.1V by about 2 hrs. The=20 voltage then more slowly drops to 0.85 to 0.9V at the endpoint where it=20 drops rapidly. So NiCd at initial 1.2V is a close replacement for Zinc Carbon. But Alkaline batteries are not. Some handheld devices designed to run=20 on 10 x NiCd or Zinc Carbon AA cells need a dummy cell when you use=20 alkaline. Although the end point is also about 0.8V to 0.9V, for a=20 substantial period it delivers 1.4V to 1.3V and initially nearly 1.6V.=20 10 x 1.3 =3D 13V, 10 x 1.6V =3D 16V, a 4W handheld CB might output more tha= n=20 it's rated power or the RF PA more easily damaged with 10 x Alkaline, so=20 they supplied a dummy cell. Liquid Lead Acid "calcium" technology jumps to nearly 2.37V on charge,=20 fully charged and is really flat at about 1.7V So not "really" 2V Gel Lead Acid behave somewhat differently and seem to have a flatter=20 discharge curve and a higher end point if you want them to last! Permenent damage usually results from over discharg of rechargeable cell. Old Nickel Iron (early rechargeable) is about 1.4V, peak 1.65V fully=20 charged on charge and dropping to about 1.2V > Sean > > > On Thu, Oct 7, 2010 at 10:25 AM, Matt Rhys-Roberts wrot= e: >> As per subject. Just wondering if anyone's got more clues than I've >> managed to find so far. >> >> Thanks >> Matt >> -- >> http://www.piclist.com PIC/SX FAQ& list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .