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At 05:11 PM 2/16/2005 +1000, you wrote:
Bill,
What would you expect the battery to show under starting load.
George ( down under)
The Hawker Odyssey PC 680 that most folks use has an internal resistance of 0.007 Ohms. A typical starter draws perhaps 200 amps in cold weather. This means that the battery voltage will drop 200 x 0.007 = 1.4 volt initially. If the battery is fully charged,the voltage will be about 12.8 - 1.4 = 11.4 volts for the first few of blades. As you continue to crank, the voltage will continue to decline. If you continue to draw 200 amps for 60 seconds (at 77 degrees F) the battery voltage will sag down to 7.2 volts.
If you do crank for this long, it might take as long as ten minutes for the battery to charge back up to 13 volts. (Of course this depends on the size of your alternator and the draw from other loads on the system.)
There are nifty charts and graphs at:
http://www.batterymart.com/pdf_files/odyssey_guide.pdf
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