Just one question.....what is this cold temperature (?C) and warm temperature (?C). Is it 0C and 20C as mentioned by Jeremy.
Prasad www.geocities.com/aquariangenius ----- Original Message ----- From: "Jeremy Maus" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, August 17, 2002 6:29 PM Subject: RE: battery temperature vs charging voltage and amps > Chuck, > > There are to ways a battery's characteristics change with temperature, > voltage and internal resistance. > > Pb-acid batteries change their voltage -.01 V per degree C or something like > that. A colder battery will have higher voltage than a warmer battery. > Also, like others have said a warmer battery has less internal resistance. > > So if you charge with a constant voltage charger the colder battery will > have a lower voltage between battery and charger plus it will have a high > internal resistance. Hence lower current. > > If you want the math here goes. > V(Voltage)=I(current)*R(resistance) --> I = V/R > Charger is 15V > Cold battery(0C) is 12V with .016 Ohms > Warm battery(20C) is 11.8V with .012 Ohms > > Current in cold battery > 15V - 12V = 3V > I = 3V / .016 Ohms = 187.5 Amps > > Current in hot battery > 15V - 11.8V = 3.2V > I = 3.2V / .012 Ohms = 266.7 Amps > > The effect of the voltage being .2V different is only about 15 Amps. Most > of the change is the internal resistance. > > The warmer battery is more efficient. If charge both batteries at 30 amps > and the warmer battery only needs 14V where the cold battery needs 15V than > the warmer batter is using less power to charge. 14V*30A=420W vs > 15V*30A=450W. > > Regards, > > Jeremy Maus > Belleville, MI > [EMAIL PROTECTED] > http://www.emidget.info
