Battery testing 101
instructions attached in PDF form and a quickie chart to leverage a volt meter. Without a carbon pile load tester (see image below) everything else is a SWAG. The cheapie hand held devices can not load a battery to the correct levels, they just load something (What it is the operator can not tell you).
Wet cell auto batteries are load tested at 50% of their cold cranking AMPS ratings. If the voltage fall below 9.6 volts the battery is bad or undercharged. Recharge at 30 amps for 15 minutes and retest. Period end of story, and has not changed in 30 years. Trust me on this one as I sold the damn things for years to Sears, Good Year, Penske, Firestone, BMW, Mercedes, GM, FORD, you name it. If they build or worked on cars this is what they use.
Batteries when they croak, tend to hold only a surface charge (Hint: read 12V or less) but drop off to below 9.6V as soon as they are load test regardless of charging frequencies or charging amp draw. If you ever take one apart (
NOTE: FULL OF ACID, DO NOT OPEN IN or ON ANYTHING YOU WANT TO KEEP AFTERWARDS), you will find the cell walls are touching hence only a few cells develop voltage. You see it as the car cranks slowly but fires up. If you turn on the headlamps FIRST then crank it will just click.
Alternators: Test and replace as the brushes in the regulator wear out after 100K or faster depending on the load. Load testing an alternator is done at the battery with the same meter shown below. Bring the engine to 1500-2000 RPM and load the system until you see 12 volts, note the alternator AMP output. It either provides steady output or not. Read diodes- Pass/fail. That is it. You can then do bench repairs as a DIY but at a shop it is a remove and replace task. No one bench tests anymore. Cheapie rebuilts have their own sad story that has been posted before.
Note: LOTS of energy usage equals faster wear. Drive at night? Drive with all the accessories on? High demand = short life. Our high end heavy demand X5s EAT batteries and have a high demand on the alternators. Fact of life.
These vehicles are energy hogs. Run great and drive like the wind though
Sorry to get so long winded on this topic.....
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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