Battery, Hopefully not alternator
 

Hi folks, I am back with another politer request for advise, after dealing with my immobilizer issue last winter my X5 is up and running now. First of all i would like to mention that last winter my battery drained and since then i have hooked it on and off for a month with a battery maintainer (Noco genius GENMini1) also please take note that my X is not on the road since December, it was just plugged in the outlet with the charger. The car starts fine but when when I use the radio (Car not running) battery charge falls like a stone thrown in the water,I know coz 3 minutes of radio then my car wont crank any more (starter ticks though). Today I finally used her to go to work. As expected after unplugging the battery from the outlet the car started without a problem, however come home time i needed a boost to get the engine started, the booster was not in a difficulty in starting my engine but then again being me I am paranoid that it is alternator related. Form home till work is 10Km and when i got home just after I switched the car off I fired the engine again and all was well. Now what I am thinking is the distance between work and home is not enough to fully charge the battery that is why i died on me at my work place? and if I continue in using my X then my battery might recuperate and normalize? Any thoughts? Thanks in advance. Also does the alternator usually fail on an M54 engine?, nearly forgot the stats M54, 2001 E53, 3.0i is my X battery is about 1 year and a half non OEM trash from previous owner. Thanks

Why not take the battery to autozone or auto stores and have them test it for you. It's possible that the battery might be bad. I've seen situation where "new" battery crapped out less than 2 years after purchase. Let the autostore test it for you and if they say it's battery then you can get one. If the battery is not the issue, maybe you are draining the battery some other way... I thought I've seen a way to test the alternator sometime back from one of the members..

Easy quick tests that only require a volt meter at the battery posts.

First access the battery in the trunk. Test voltage at the Battery terminals without vehicle running. see tables below to determine your battery condition.

Temperature Compensation Table

Open Circuit Voltage Approximate State-of-Charge at 80°F (26.7°C) Hydrometer Average Cell Specific Gravity Electrolyte Freeze Point
12.65 100% 1.265 -77°F(-67°C)
12.45 75% 1.225 -35°F(-37°C)
12.24 50% 1.190 -10°F(-23°C)
12.06 25% 1.155 15°F(-9°C)
11.89 or less DISCHARGED 1.120 or less 20°F(-7°C)

DURING the load test, the voltage on a good battery will NOT drop below the following table's indicated voltage for the electrolyte at the temperatures shown:
LOAD TEST
Electrolyte Temperature °F Minimum Voltage Under LOAD
100° 9.9
90° 9.8
80° 9.7
70° 9.6
60° 9.5
50° 9.4
40° 9.3
30° 9.1
20° 8.9
10° 8.7
0° 8.5

There is a longer BATTERY test attached in PDF format with pictures and correct processes.