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  #11  
Old 01-10-2020, 09:50 AM
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OP: A proper charging system and battery is required before any electrical tests are performed. Anytime battery voltage drops below 9.6v all kinds of faults pop up. As cars get older and on newer cars, the demand on battery capacity gets more extreme. Average life span of a battery is 3 years. If you use a "battery tender/trickle charger" religiously every time the BMW is parked for more than 24 hours, you can get 5-8 years!

You can do a few quick tests before you pull off the alternator to determine battery/charging system failure. At this age and mileage the brushes wear out and give an intermittent to no charge swings, making lots of issues as mentioned.
Step 1. Remove and clean the posts at the battery. Remove and clean the positive jump point under the hood at the driver's side firewall. Remove and Clean the positive cable at the alternator (note: do this step while you have the battery disconnected)
Test one: With a volt meter on the battery posts do the following tests
- Key off, read battery voltage
- Idle read voltage
- 1500 RPMs hold for 1 min and record highest and lowest voltage
- 2500 RPMs see above
Note: You are looking for ANY fluctuation that would indicate charge/no charge, Example volts read 13.7 then drop to 12.3 then up again. It will be normal to see 13.5 to 14.1 for example while running the tests. To make the test simple turn on a few high load accessories (headlamps, heater blower, seats, rear defroster)

Last test
Engine off, turn on headlamps on (key needs to be in Acc position 1) and turn on seat heater, blower on high and rear defroster) for 15 secs or so.

Read battery voltage. If voltage is below 12.6, charge battery. If you have a less than a 15 amp charger, charge over night and reread battery voltage. When cell walls collapse in a battery, the battery will hold only a surface charge then croak when you apply a load over 100 amps for 15 secs. Hence why you need a carbon pile tester to truly test a wet cell battery. Yes there are capacitor based testers that will get you into the 85% range of accuracy for those who follow the tester world.

Note: If your battery has lots of white crud all around the posts, save yourself lots of pain and throw it away before you waste any more efforts...
Note 2: Make sure your ground cables are attached and clean as well. There are a few on the engine, frame points etc. How to test? see image attached)

Report back!

What you are doing here is to see if the battery and charging system are working properly without the proper tools like a carbon pile load tester. This type of tester allows you to properly load a battery and then the charging system to read true out puts rather than SWAG (scientific wild ass guesses) from internet postings. The tests I recommended will take a few mins and it will provide a lot better result than the local parts store's happy meter.

Typical Charging system demands
Equipment Electrical Draw
Rear Window Defroster 25 amps
High Blower 20 amps
Headlamps (Low beam) 15 amps
Windshield Wipers 6 amps
Ignition 6 amps
Brake Lights 5 amps
TOTAL 77 amps


See chart below for battery health results.


Helpful?
Attached Images
   
Attached Images
File Type: pdf How to test a Battery.pdf (477.2 KB, 19 views)
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2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green

Last edited by StephenVA; 01-10-2020 at 10:31 AM.
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  #12  
Old 01-10-2020, 10:55 AM
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Location: Hamilton, Ontario
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Will do , awesome info. As background on the electrical system. The battery is a couple years old. The alternator history is a saga. The alternator died 4 years ago 2 hours from home on a weekend. Had it towed and alternator replaced at Canadian Tire( had no choice). 10 months later that new alternator failed, was replaced under warranty. This alternator is now 3 years old but I don’t have a lot trust in it for obvious reasons.
Will complete the tests/ cleaning and report back. Thanks again!!
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2006 X5, 3.0 L
232,000 km
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  #13  
Old 01-10-2020, 12:47 PM
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Good luck
Canadian tire was a customer of one of my old companies in a previous life. Well meaning but driven by price first
Alternator was more than likely a reman unit so all bets are off on quality
__________________

2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green
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  #14  
Old 01-10-2020, 01:07 PM
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Join Date: Jan 2016
Location: Hamilton, Ontario
Posts: 12
Mark1998 is on a distinguished road
Totally agree on the Canadian Tire comment. That is why I inserted the “no choice “comment. At the time I felt lucky that they had an alternator that fit so I was not stranded.
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2006 X5, 3.0 L
232,000 km
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