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Discussion Starter #1 (Edited)
We have a 2006 Commander with a 3.7 V6. We are changing the battery and need to know if anyone can tell me what the Maximum mili amp draw with nothing on would be. Also what the charge rate in voltage I should see on a multimeter at idle and 2500 RPM. Thanks!!!!!!!! :)
 

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Thanks SAL, I put a new battery in a little while ago, checked the draw off the negative cable and it dropped to .010 amps. Now I,m looking for a charge rate in volts to make sure the alternator isn't over charging.
 

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Just in case you didn't know or for others wondering how to do it. There are a couple of ways to test the draw. The most common is using a multi meter. One way is to disconnect one of the the battery cables and put your meter in line between the cable and the terminal. I've heard of people plugging in battery charges threw the power port then getting it all hooked up pulling the charge then taking the measurement. I don't use that method but putting the meter inline I have using the positive side. Make sure the meter is on auto or set the range to 100MA.
 

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Charge voltage is always the same (12V systems) regardless of the vehicle.....13.8 to 14.2 with a fully charged battery......as high as 14.6 after startup but will drop back within a minute or two.
Unlike vehicles of the past, the charge rate is controlled by the ECM.....there is no regulator.....the ECM varies the field voltage.

Rob
 

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The ECM/PCM will vary the charge voltage dependent on the Battery Temperature, usually a simple temp sensor in the battery tray. The colder it is, the higher the charge voltage "set" by the ECM/PCM.

Again, I'm a Commander Newb, but very knowledgeable on vehicles and Chrysler Vehicles in general, if I'm wrong, please correct me, this is the way Chrysler does it on just about all their vehicles.

Basically, I have observed, below freezing expect the full 14.6Volt, Hotter Summer day, expect the 13 some volts.

Yes, as the battery charges, it resistance will change, and that can vary the voltage depending on how well the alternator can supply the required current. With a good battery and charging system, I have seen almost no change after start to driving for hours, system voltage varied by temperature only. (Even though the sensor is in the battery tray, its seems to vary with the Outside Air Temp pretty closely.)

A bad battery can draw way too much current and that will drag down the system voltage, which the low voltage can cause all sorts of electric items to operate strangely. That is why you'll hear stories where people replaced the battery and suddenly all of their electrical gremilins were gone.

Most of the vehicles from the 90's on, with the ECM/PCM smartly controlling the system voltage, do a much better job holding voltage. I have an underdrive pulley on my '99 Neon R/T, and the charging system holds voltage, except in very cold weather with everything electric item on in the vehicle and the motor at idle, at that point, voltage will start to drop as it drains the battery, more than a few minutes at idle under those conditions and I get the charge light with voltages down at 9 volts if I don't rev the motor with the clutch pedal in.
 
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