Won't run without battery connected...

[slowlanemcvane]

I can speak on this matter myself, having recently (within the last 18 months) replaced the alternator on my wife's 2007 X5 4.8i (4-zone, of course).

It definitely points to a bad alternator, but as said above, never, never, NEVER disconnect a battery from a running car built much more recently than 10 years ago. The electronics and electrical systems are a lot more sensitive and fragile than they were in cars even 15 years ago.

I replaced the alternator on my wife's car, with a brand new Autozone alternator. I got mine for $150 out the door, and it has given me 18 months and 20,000 miles of flawless, silent operation. I don't know what year your car is, but none of the parts retailers in my area had the high-amp alternator for the 2007, so the tech at the Autozone (normally, tech and Autozone is mutually exclusive, but this guy knew his stuff) looked at 2008+ X5, and came up with a compatible part that fit and worked exactly as the OEM part did.

Cheers.

[onebad7up]

The x5 made it back to the house.

Picked up the battery from batteries plus at 12.36v. Installed it and drove 3 miles to the house. Let it sit one hour and the battery measured 11.7v.

Started it up and it went to 13.7v. And gradually increased into the 14's. When I reg the vehicle, the voltage drops back to 13.7v.

Also, the radiator can kicked on and the voltage dropped while it ran.

Does this make sense?

[jfoj]

If the battery surface Voltage was only 12.36 Volts when you picked up the battery, it is not fully charge and/or is bad.

A fully charged battery should have a 12.6 Volt surface Voltage, it sounds like your battery is at least 50% discharged assuming it does not have a problem.

A large battery may take 6-8+ hours to charge. AGM batteries sometimes have longer charging time.

Typically charging Voltage should be between 13.5-14.5 Volts. My E70 runs right around 14.0 for the most part.

[onebad7up]

If I put a load on it ( ie. Lights, heater fan, etc) what should the voltage be? I would assume that it would not drop below 13's. correct?

[jfoj]

13.5-14.5 Volts is the typical charging Voltage of most modern vehicles.

There is an exception to some models, not the E70, that the engine control computer will actually turn off the alternator as a fuel savings and performance boosting measure. These vehicles usually have a current loop on the output of the battery and/or alternator to monitor power usage so the computer can control the alternator.

[onebad7up]

I am thinking its alternator. just flew back from Indy and measured the voltage again. It has been sitting since yesterday at noon.

11.7v with key off.
11.5v with engine idling
11.3v with engine idling and blower fan on high and high beams on.

[ard]

There are so many modules you can damage by F-ing with the battery when it is running...modules that have 4 digits in their price tags.

I appreciate the DIYer spirit. Kudos. Kudos for recognizing the codes were all spurious....But this is not a 1970 VW bug that you can take the battery out, lean a shoulder into it on a flat parking lot, get it up to 3mph, pop the clutch and drive 100 miles home!

[jfoj]

With any modern vehicle it is hard to really verify things if the battery is not fully charged.

I would clearly question the alternator, but with a battery at 11.7 Volts all bets are off. With the IBS and other things in this vehicle, you cannot always assume things are as you think with a low battery.

I KNOW for a fact that the E70 has a very hard time notifying the driver there is a charging system problem. I have had my E70 about 3 times not charge at all and there were no warnings. I run an UltraGauge an have Voltage and temperature threshold alarms which I have seen the vehicle not charge at all for miles. I have pulled over and restarted the engine and the charging has come back to normal. I am question the regulator in my alternator, will probably replace it proactively here shortly.

I do not know why anyone that frequents forums does not own a decent battery charger at a minimum.

Do not just get a battery maintainer, these do not have enough current to really charge a battery.

These are nice chargers, they will actually "maintain" as will as I have been using mine on one vehicle and if I open the vehicle up, it will automatically kick back into charge mode when it sees the battery Voltage or Percentage of charge drop -

http://www.amazon.com/SOLAR-PL2310-P...W2T0VR46GRDG1A

http://www.amazon.com/SOLAR-PL2320-P...W2T0VR46GRDG1A

http://www.amazon.com/SOLAR-PL2520-P...s=SOLAR+PL2520

[wsmeyer]

You people are really paranoid. There's no black magic going on inside a battery. When the engine is running the battery is just a simple resistive load, and not a very large one at that. The radiator fan draws roughly 5 times the amp as the battery and the electrical system has no problems with that cycling on and off.

[A B Able Truck]

Originally Posted by jfoj

12.03 Volts is LOW. I put my X5 on a maintenance charge about once a month.

A good idea, especially for the short commute driver.

What Causes Car Batteries to Fail? – Battery University

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