Electrical Systems of Today
We all dread that moment
when we're getting ready to go to work, get inside our vehicles, turn the key
and.... click, tatatatata.....or silence....
Oh yes...should have replaced that battery! No
problem. You find somebody to jump the car, drive to the nearest auto parts
store and have somebody replace that battery for you. Problem fixed. Of course,
this scenario is very general and doesn't apply to any modern BMW of today. In
fact, soon it will probably not apply to any car in the near future.
BMWs have always been at the forefront of technology.
Over-engineered is an understatement when it comes to these cars. A late model
BMW has such a complex power/charging system that one needs to have a degree in
electrical engineering to be able to fully decipher. It all starts with the
battery of course. Absorbent Glass Mat (AGM) batteries have been pretty standard
in these and many European cars for their many benefits. Among the advantages of
an AGM battery are:
-
Spill proof
-
Low maintenance
-
High current on demand
-
Cold weather performance
As durable as these
batteries last, nothing lasts forever of course and when it's time for
replacement, this is when things start to get interesting. If we go back to the
earlier scenario, steps must be taken before and after replacement of the
battery to meet and follow the manufacturer's original design criteria. If these
steps aren't followed, the vehicle will self-destruct! Ok, so maybe not. Just a
little stretch of the imagination. What could potentially happen is a multitude
of warning messages and electrical gremlins that may result. This can lead to
unnecessary diagnostic time, to uncover a problem that shouldn't have happened
in the first place.
Over the course of a battery's
life span, many factors influence the way the vehicle's charging system
keeps the battery fully charged. All these factors are constantly been evaluated
by various sensors and control units engineered into the vehicle. IBS or
intelligent battery sensor keeps track of the battery's state of charge,
continuous measurement of current, and acid temperature, among other things. The
various microprocessors in the vehicle take this information to calculate how
the battery should be ultimately charged and influence vehicle electrical
behavior. Lets say you accidentally leave a map light on. Theoretically, there
should be a programming logic that is designed to shut that particular circuit,
should the battery reach a certain level of charge. This is true as well when
you have the radio running with the car off. After reaching a predetermined
amount of time, you would get a message indicating it is time to shut off the
tunes, or start the vehicle to avoid further battery depletion.
When a breakdown does
occur, one needs to investigate and perform a systematic diagnosis of the
source of the fault that will lead to a lasting solution to the problem. Energy
Diagnosis is such a test. Built into the BMW diagnostic software, this test
needs to be done BEFORE battery replacement to find out why that battery went
down in the first place. The vehicle stores a "profile" of how the vehicle is
driven over the course of 30 days. This can lead to the source of battery
depletion. Did something "wake up" the car frequently, i.e. alarm system, lights
switched on too long, faulty control unit? Was the vehicle driven for very short
distances? Or did the battery just failed because it reached the end of its life
span.
Once a diagnosis is
obtained, a repair is made as necessary and the battery replaced, one
final process needs to be performed AFTER replacement. The new battery needs to
be "registered" to the vehicle. This effectively deletes the driving profile and
a new profile is made to take into account the new battery. As such, if a
battery is replaced and the vehicle doesn't know this, that new battery will be
treated differently. This is what will lead to those warning messages and a
battery that won't last a year. Furthermore, if a battery is replaced with that
of a different capacity and/or different amps per hours, one must perform a
battery "retrofit". This achieved by means of programming to be able to let the
vehicle know of the change.
So the method of actually
replacing the battery is the same, it is the way this replacement is treated
that has changed. This is one reason why we in this industry need to keep up
with this changing technology. Lesson learned. BMW hides "Uncle Sam"
inconspicuously in your vehicle to keep track of your electrical system.
