I am not "uneducated" concerning the various rechargable batteries types, nor am I uneducated in the various units like energy/joules, charge/coulombs, maH, capacitance, etc. I have been involved in electronics engineering for over 25 years. Its pretty rude to assume that I dont understand these things ( I dont post on things I dont understand ) and I posted nothing to the contrary. When I stated the "capacity" of a battery being "nearly gone" you and every normal person on planet earth could understand I was using common real world rechargeable batttery usage terminology, not a strict, confusing to a layman, electronics term. And mAH rating and Energy "capacity" (layman terminlogy used here again for the word capacity) are virtually the same thing on a given cell because a given cell has a relatively fixed voltage. So it sounds to me that you are the one a little confused here not me. i.e. a 2000mAH battery stores twice the energy of a 1000mH battery when fully charged.( Assuming same battery voltage - which I did because thats all were were talking about was one battery ).
And you never answered my key question in the post, what is the intial cell voltage under the .350 amp load?? Is it only 1.1VDC or not? -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Cory Papenfuss Sent: Friday, January 26, 2007 8:24 AM To: Pentax-Discuss Mail List Subject: RE: about NiMH batteries (was: aliasing/moire) > I dont understand what you are saying. Of course they Apparently. > 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 Capacity in terms of what? Energy or mAH... they're not the same thing. Check a book on physics... one is Joules, the other is Coulombs.... the amount of charge a cell can provide says nothing about how much work it can do until you know the voltage it provides it at. > 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 <skipping confusing drivel...> Cell capacity is defined in terms of the "C-rate." That's the amount of current they can provide for 1-hour. Actually, as you say, the test is typically done at the C/10 rate... in other words the C rate is 10x the current the battery can provide for 10 hours. Some battery constructions (even with the same fundamental chemistry like e.g. NiMH) can provide significantly different output voltages under the same loads. If the voltage-current (i.e. power) integrated over time (i.e. energy) is lower, the energy output is lower. Batteries are NOT rated in terms of energy.... mAH has nothing to do with energy until a voltage is defined. Now, if you cannot wrap your argumentative self around these things, please either keep it to yourself or be willing to be educated. -Cory > > -----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
