I dont understand what you are saying. Of course they are not dead at 1.1 volts under load, what I said is any nimh battery is nearly gone ( almost dead as a percentage of the total capacity it gives or gave ) once you go below 1.2 vdc on the cell regardless of load. If you are getting another 0.1 volt drop on these cells with a .350A load, the total additional series R is only about 0.3 ohms which is still quite low for a AA cell if that is what we are talking about here. In any case, I dont think most AA cells will give you the full maH rating under a 0.35 amp load, its just too much and I believe the maH ratings are done with a much smaller drain current to be fair to the battery makers. And your last statement is only true under high load conditions because the internal resistance is a much lower loss factor under normal or low load conditions. And what your seeing as "higher internal impedance" is not fixed, it varies as the cell discharges. Your not saying you only get 1.1 VDC output on these cells at the start of the 0.35A discharge cycle are you? jco
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Cory Papenfuss Sent: Thursday, January 25, 2007 6:50 PM To: Pentax-Discuss Mail List Subject: RE: about NiMH batteries (was: aliasing/moire) On Thu, 25 Jan 2007, J. C. O'Connell wrote: > If I am not mistake, NIMH batteries all have > appox the same internal resistance and its very > low compared to Nicad for example. specifically > what kind of load are you draining them at and what > is the output voltage of the cells under that load? > Once a nimh drops below the rated voltage of 1.2 VDC the charge is > nearly gone regardless of load... jco > I'm using a LaCrosse BC-900 charger. It will cycle individual cells under a constant current charger or discharge, while integrating the total charge/discharge mAH capacity. As such, it's a constant current charge/load... not a constant resistance. The cells I'm referring to are Powerex 2150 mAH (IIRC), and I did the cycle at 700mA charge, 350mA discharge.... That's roughly C/8 discharge rate, and I obtained approx 2000mAH before dipping below 1.1V. On these cells, they're not dead at that rate until they get between 1.0 and 1.1V... on the Energizer cells it's much closer to the 1.2V you specifiy. Bottom line: Cheap cells illustrate a higher internal impedance than higher quality cells... even at the same mAH rating. That means they don't last as long before the camera thinks they're dead. -Cory -- ************************************************************************ * * Cory Papenfuss, Ph.D., PPSEL-IA * * Electrical Engineering * * Virginia Polytechnic Institute and State University * ************************************************************************ * -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
