[V8] My V8 is eating batteries

NicolCS at aol.com NicolCS at aol.com
Wed Nov 30 02:47:17 EST 2005

You could have a small drain that's killing the battery, a bad charging 
system, a bad cable/connection, or a string of bad batteries.  

Charge the battery with a good charger, then disconnect the battery and let 
it sit for a week.  If it's still good when you reconnect a week later, the 
battery is OK

WIth a charged battery, measure the voltage at the underhood terminal while 
cranking the engine.  If it stays in the 10.5-11V range, your cables are 
probably OK

After starting the car, again with a reasonably charged battery, measure the 
voltage at the battery while the engine is running and the lights ON.  It 
should measure 13.5 to 14.5V.  Less means a charging system fault.

Finally, check for a battery drain. Remove one battery cable and secure a 
25W, 1-ohm resistor between the cable end and the battery terminal.  Set your 
voltmeter to the lowest scale; like about the 1 or 2 volt scale.  Remove IG key 
and open and close the driver door to switch off the retained accy power 
feature. Measure the voltage across the 1-ohm resistor.  It should read .01 to .03 
volts (max).  If the voltage is more than .03, then something in your car is ON 
and draining the battery.  Alternator, trunk light, radio, courtesy lamp.  
Pull and replace fuses one by one until you find the faulty circuit and the 
voltage drops below .03.  Note: You will have to disconnect the large alternator 
wire to check the alternator as a potential source - that line doesn't have a 
regular fuse.
Craig Nicol
90 V8Q Cayenne

<snip>Am I looking at a problem with the voltage regulator, alternator, or 
more serious electrical problem? Thanks!<usnsip>

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