72 W108 4.5 - How Long Should The Good Battery Keep Its Charge

[napster]

How long should the battery go between driving before it does not have enough juice to crank the engine.

I have a 72 280se 4.5 and I am finding that the battery does not hold its charge more than a week. I try to drive the car on a weekly basis to keep the battery charged and drive about 15 miles. The driving route is a mixture of local and highway. The battery was replaced last year and is the correct size CCA rating. Is there a current draw one these cars when they are parked.

[Usaguy]

Originally Posted by napster

How long should the battery go between driving before it does not have enough juice to crank the engine.

I have a 72 280se 4.5 and I am finding that the battery does not hold its charge more than a week. I try to drive the car on a weekly basis to keep the battery charged and drive about 15 miles. The driving route is a mixture of local and highway. The battery was replaced last year and is the correct size CCA rating. Is there a current draw one these cars when they are parked.

All cars have a small amout of draw but it shouldn't be more than 0.1 amps (100 miliamps).

Something in the car could be draining your battery.

Do this with the ignition off and doors/trunk closed:

Get an amp clamp and put it over the negative battery cable and see how much it draws. You can also use the amperage meter setting on your multimeter but you will have to disconnect the negative cable and put one probe on the cable and one on the also negative post

Here's an example how long it takes to completely discharge a typical car battery (60AH) with a 50 miliamp draw:

60/0.05 = 1200 hours / 24 = 50 days / 7 = little over 7 weeks.

The point of non starting will be sooner than 7 weeks

[Diesel911]

Engine not running:
Personally I would hook up the Voltmeter to the battery and watch the meter as I pull one fuse at a time. I you pull a fuse and the voltage rises you have identified a possible circuit that there could be trouble in.

Do the same but disconnect the wires from the Alternator or if it has a remote regulator from the regulator.

Get in close the door buckle up and stick the key in the ignition. Don't attempt to start or actually turn the key but stick the key in the Ignition and slowly giggle it around while watching the voltmeter for changes in voltage.

This is an odd one. On my Mothers Car the top of the Battery got so dirty and scummy that the scum was conducting some electricity between terminals. It was magnificent because she often walked to work and when she did drive the car it was usually for less then 5 miles round trip.
I was probing with the voltmeter and stuck one probe into the scum and I got some small number of voltage (this was back in the 1970's so I don't remember the reading).
I cleaned the top of the Battery and She stopped having it cause issues. Note Batteries back then were not as well sealed as they are not.

Charge the Battery and take it to be load tested just to be sure it is not the Battery itself.

[napster]

Thank you gentlemen. I will investigate and see what I can find.

[aluminum]

Simple Just disconnect the Battery say for a Month hook it back up and it should be Still fully charged and start no Problem , Evan 2 or 3 months on a good battery .

That's a good short test , So once your convinced you have a short just find it

( if the Battery go's dead / down that fast you should be able to see it arc when you Hook it up most likely, your clock is not going to kill the battery in a week or more )