bmwmaniacboy

I have a 520D E60 and when I power the car off, in a few minutes I get a battery low warning error and eventually car shuts off. Then I have to reset the time again.
I charged the battery for the first time yesterday and was fully charged after 5 hours using 0.2A Slow and 20A Fast charging.

The Voltage on the battery is 12.47V and when its running its 15.2V
When I drove it after the charge, powered it off and about 3 mins the battery warning came up again.

Any replies much appreciated

BimmerFan52

If the voltage after fully charging the battery and then driving was 12.47V then it is likely time for a new battery. Also, you should check to see which battery you have: a white top indicates a FLA (flooded lead acid) and a black top indicates an AGM (absorbed glass mat). 15.2V is on the higher side of voltage output, and may indicate that the IBS is signaling the CAS that the battery state of charge is low, and in turn ramping up the system voltage to accelerate charging.

In the US, auto parts stores will test batteries and alternators for free using a computerized tester. You may want to check for that same service in Ireland. The computer simulates a load test, which in the past was the only sure way to test a battery, but today's digital units have gotten pretty good.

Some tips:
- A healthy fully charged battery will read approximately 12.65V, and if the battery just finished charging it can be even higher, as a surface charge on the plates will cause higher readings. To get an accurate voltage reading the battery should sit idle for up to two hours after charging before taking a voltage reading.

- A normal output for the alternator is 14.2V - 14.4V, which is about the optimum voltage for charging a battery. Based upon the state of charge and age of the battery, the CAS may send a signal to the alternator to increase current output, which in turn increases system voltage. 14.7V is the maximum the alternator should ramp up to for an AGM type battery, while 15.5V is about the maximum the BMW alternator will use for FLA batteries. The IBS has a built in temperature sensor that monitors the negative battery terminal temperature to insure that excessive charging voltage does not begin to boil away the battery water.

- The normal failure mode of batteries is due to sitting for long periods with less than a full charge. When undercharged, a chemical reaction in the battery coats the plates with a sulfur compound which prevents future charging. This coating process will continue if the battery is undercharged until it no longer will take a charge. A good investment is a battery tender, which if you have a private garage can be left on once per week to keep your battery voltage "topped off". You want the computerized type that has three phases of charging and can be left on indefinitely (you mentioned a charger and you may have this type already).

- You may also have a parasitic drain, which is something in the car's power system that is drawing power even when the engine is off and has set idle for hours. BMWs are know to have several components that if they go bad, will drain the battery. If you do have a parasitic drain, a new battery will also be drained in short order.

- Multiple short trips can also cause the battery to run down. Each time you start the car you draw more battery power out than the next short trip can put back in. Eventually the battery won't start the car. Another good reason to have a battery tender.

- You may also want to invest in a cigarette lighter plug-in type voltmeter, which is very handy for monitoring system voltage while driving. You may discover as I did that your alternator voltage regulator is going bad if system voltage occasionally sags too low.

Wkistler23

I would have the following checked by a professional:

Alternator
Battery
IBS

How old is your batter? If older than 5 years, on to the next one. What is the color of the battery "life" indicator? Green/Yellow/Black

If the battery is new, then have the alternator tested. A local parts store or indy repair shop are fully capable of doing this test.

If the battery and the alternator are fine, but your power is still being drained, you should consider replacing the IBS (these tend to go bad). The date and time resetting is typically an indication of the IBS failure.

I hope this helps.