:iagree:

Small update
 

Sorry to see argument on this post.

This morning I am going to get the x5 towed to my house. I tested at terminals yesterday and got a 10v read.

When I get it to my house I will charge it and take it and measure volts again.

After that go to autozone and check it.

After that remove alternator and take it to get checked..

Not buying any parts until late I do get my car at my house because it's to hard to do test in another city without my garage.

Alot of the info has helped me.
I'll get back once my car is at my house and battery has charged.

Originally Posted by jdstrickland
The red battery light is really a Charging System Light

Guys, This light will turn on if the charging system sees a "out of limits" (bounds) voltage in the charging circuit. It does not know anything other than volts. A shorted (collapsed cell walls) battery, a dead or dying alternator regulator, poor contact in the Alt brushes, a break in the charging circuit (Alt wiring, battery wiring grounds, etc) all can cause the light to turn on. The one I enjoyed in the past is the four way flasher indicator turned on but does not blink when a battery started to collapse and shorted out. Car started and ran fine. No codes.

Bredliner is correct as always, there is more than one way to test our vehicles leveraging the onboard monitoring. But be aware, that is monitored voltage not a live reading. All of these displays are processed by the CPU (DMU?) then displayed. In a vehicle that is normal it is good enough for 99% of users.

Under the heading of "So What?" I hold a Master SAE certificate. But I don't think that moves my random thoughts and postings to "Master Levels" as this is a DIY forum. I have seen many "masters" arguing about lots of fine points including my own two electrical engineering Master degree brothers who have ZERO auto experience. I have a lowly general technical engineering education background, so I don't count at home either.....

I think the bottom line here for all users is to double and triple check the starting /charging system voltage as everything is suspect on a 10+ year old system where you are not the only one who touched it first. Who knows what wire was left loose, or has gotten worn out or stressed out in the last few years? Batteries die every day some new some way older than 11 years. Check and test them before moving forward as batteries and wire connections and grounds will lead you way from the problem to the parts replacement process real quick. A quick jumper wire to provide a known good ground may display a weakness.

Thanks for the update. Good testing process. 10V is really low for a static state of a battery. the recharge will show the real battery state. Hopefully it is just brushes in the alt that are too worn to make contact. See other postings on DIY for brushes and alt reg fixes. Most seem to go down the replacement path with varied results from the part sources.

Let us know of your results

And in many parts of the automotive field I am in fact an expert. Trained, certified and made my living in the field for many years.

Um, no not related that Trader4 in any way shape or form. He was a real PITA and in case you have not noticed he deleted all of his posts a week ago or so from what I saw. He was a real PITA that offered nothing much to the forum members that were looking for help.

Vehicles are not all created equally, but there is something call Voltage drop that need to be taken into consideration AND keep in mind here, we are discussing BMW's. Our friends the Germans tend to do things a bit differntly then the rest of the world. Just because you may think you understand how a BMW is built does not mean you understand how the electrical system works.

The E53 and many other BMW's connect many of the electrical loads directly or very close to the battery, this does not mean the battery is meant to run or power the vehicle for extended periods of time, the Alternator is the PRIMARY DC power source for most modern vehicles.

BMW has the BST or ballistic battery cable that can and does go bad, but the purpose of this BST cable it to shed the vehicle load in case of an accident and reduce a fire hazard due to electrical problems.

But not all vehicles have connections directly at the battery. Many vehicle have load centers and/or larger fuse and relay centers that may or may not be located near the battery depending on the vehicle design.

So for someone to continue to state that the the vehicles loads are powered by the battery, this is flat wrong. I am not sure where this was learned or how this idea came about, but it clearly needs to be revisited.

The alternators primary purpose is not to be a battery charger. Until this concept can be understood, there will be no forward progress.

No arguments, just people that do not understand or want to understand!

10 Volts at the battery or where every you measured is BAD.

A fully charged 12 Volt battery should have a terminal Voltage of 12.6 Volts.

Just because the batter has 12.6 Volts does not mean it is a good battery.

A battery can have a surface charge that is greater than 12.6 Volts, but this can quickly be removed by turning the headlights on for 30-60 seconds, then let the battery rest.

Until a battery is properly charged and tested, you have no idea what shape it is in.

Problems as mentioned, could be with loose or corroded terminals, a bad BST cable and even a bad alternator.

Keep in mind that some of these vehicles also have bad engine to body grounds as well.

If you have a battery charger that claims the battery is 100% charged, you cannot use this 100% value to consider the battery any good. The battery needs to be tested with a load tester and/or a resistive/capacitive battery tester. I prefer both.

A poor mans load test is to monitor the battery terminal Voltage on a fully charged batter, turn the headlights on and if the battery drops below 12.2 Volts, I would likely condemn the battery, but always best to have a proper test preformed.

No loss. He really was a PITA that did not offer any help just whining about this part or that one and at BMW in general.