Bad batteries or current draw?

[samer0214]

About 2 months ago, I replaced the battery that came in my 2005 4.8L with an Exide battery, because the old one tested with a bad cell.

Less than a month later I had to exchange the Exide for another one because that one failed with a bad cell! A few days ago the truck wouldn't start after having sat undriven for a little more than 24 hours. I had to jump start it and it's been starting fine since.

Both the battery and alternator tested good at my mechanic's shop, but he told me that he has not had very good luck with Exide batteries over the years, and when I asked him about checking for current draw/leak, he said it's hard to test for those because of the various modules on the car that are constantly drawing power.

So which is it: Bad luck with batteries? Problem with Exides overall? Current draw?

Is it in fact hard to check for current draw on our trucks, or is there a procedure for checking?

[Zulu95]

I just changed out an Exide battery last year. It only lasted 12 years or so.
Check out this post for info on the "Sleep" mode.

Light on Steering Column won't go off? - Bimmerfest - BMW Forums

[samer0214]

Originally Posted by Zulu95

I just changed out an Exide battery last year. It only lasted 12 years or so.
Check out this post for info on the "Sleep" mode.

Light on Steering Column won't go off? - Bimmerfest - BMW Forums

Zulu: I think you meant to say 12 months or so? 12 years for any battery is unheard of!

What did you replace the Exide with?

[Zulu95]

Originally Posted by samer0214

Zulu: I think you meant to say 12 months or so? 12 years for any battery is unheard of!

What did you replace the Exide with?

Nope - 12 years. I could hardly believe it either. Fitted by my indy November 2004. Replaced 2/16/2016. I'll have to dig out the paperwork to refresh my memory on the replacement. It was the top of the line before you got into exotic boutique makes in the local tire/battery place with a reasonable warranty/price ratio.

[sunny5280]

Checking total current draw is easy...turn everything off and place an amp meter inline with one of the battery terminals (start with the highest amperage rating the meter offers and work your way down).

If you want to determine the current draw of a particular circuit you can determine it by performing the above and then remove the fuse for the circuit of interest. Subtract the two and the result will represent the current draw of the circuit.

Do not attempt to start the vehicle with the meter inline.

[samer0214]

Originally Posted by sunny5280

Checking total current draw is easy...turn everything off and place an amp meter inline with one of the battery terminals (start with the highest amperage rating the meter offers and work your way down).

If you want to determine the current draw of a particular circuit you can determine it by performing the above and then remove the fuse for the circuit of interest. Subtract the two and the result will represent the current draw of the circuit.

Do not attempt to start the vehicle with the meter inline.

What modules should I disconnect? Which ones have the potential to stay awake if there were to be a malfunction?

[sunny5280]

Originally Posted by samer0214

What modules should I disconnect? Which ones have the potential to stay awake if there were to be a malfunction?

Unfortunately I cannot help you with this. Perhaps others here can offer their suggestions. However you could just go through each one, fuse by fuse, and see what level of current draw each has.

[Fifty150hs]

Originally Posted by samer0214

What modules should I disconnect? Which ones have the potential to stay awake if there were to be a malfunction?

Start with radio, NAV and telematic (blue tooth module). Pull fuses for all of them and start putting them back in one at a time. When you insert one that results in a dead battery, you have your culprit. Had a similar problem after alternator took a dump. New alternator and new battery and it kept dying over night. Parasitic drain turned out to be the telematic that wasn't "going to sleep" like it was supposed to. Removed the telematic and problem solved. Best of luck!

[samer0214]

Originally Posted by Fifty150hs

Start with radio, NAV and telematic (blue tooth module). Pull fuses for all of them and start putting them back in one at a time. When you insert one that results in a dead battery, you have your culprit. Had a similar problem after alternator took a dump. New alternator and new battery and it kept dying over night. Parasitic drain turned out to be the telematic that wasn't "going to sleep" like it was supposed to. Removed the telematic and problem solved. Best of luck!

Just to be clear, this diagnostic should start after the truck has gone into sleep mode, at which NONE of the modules should be "alive" after 16 minutes?

On a perhaps related note, when the headlight switch is in the automatic mode (leftmost position), the lights are always ON regardless of ambient light level, they do not turn toggle, as if the light sensor/module is stuck in the always ON mode. Lights do go off when the car is shutoff. Related? Is there a separate sensing module for that function? Could it be the culprit?


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[Fifty150hs]

Originally Posted by samer0214

Just to be clear, this diagnostic should start after the truck has gone into sleep mode, at which NONE of the modules should be "alive" after 16 minutes?

On a perhaps related note, when the headlight switch is in the automatic mode (leftmost position), the lights are always ON regardless of ambient light level, they do not turn toggle, as if the light sensor/module is stuck in the always ON mode. Lights do go off when the car is shutoff. Related? Is there a separate sensing module for that function? Could it be the culprit?


Sent from my iPad using Tapatalk

The sensor for the automatic headlights and automatic wipers is on the window by the rear view mirror. It's concealed by the black cover behind the mirror. Have you or the previous owner changed the windshield using non-BMW glass? When I changed mine it stopped working. You may also have a bad module. If you take the cover off you can unplug the sensor and see what happens. The cover is shown as number 6 here: RealOEM.com - Online BMW Parts Catalog