As you may know, the 11-year-old factory original battery in my '00 300m
struggles a little when starting the engine when the car has been
sitting for a few hours in below-freezing temperatures.
When the temperature is below 25F, and especially below 20F, cranking
the engine to start it is often accompanied by erratic behavior of the
5-disk CD changer (flashing lights, mechanism operating like I've just
loaded a CD). On one occasion, the CD player's lights kept flashing for
the entire time the engine was running.
So I would assume that the car's electrical system is experiencing a
significant under-voltage condition on those occasions. My question is
- does the ECM module not detect such a condition, to the point where it
might (or should) generate a fault code, flash the "check engine" light,
Are there any fault codes for a '00 300m that would correspond to
something like "hey - the battery has reach the end of it's life" code?
(ie - battery under-voltage detected) ?
The battery warning light on the LH cars is not an idiot light, it
actually represents a trouble code. In other words, is switched on by
the computer, not a simple amp sensor. The conditions that cause the
light to come on are listed in the service manual, but generally are
faults in the charging system, not the battery itself. The system
doesn't know what is going on inside the battery. (Unlike some consumer
products, there aren't sensors and battery health readings reported to
the computer.) The charging circuit knows how much it is exciting the
field to produce current, but without an amp meter you know know how
much current is being sent to the battery.
Your best measure of battery health is the color of the eye (if so
equipped), and how the battery behaves when starting. Heat is the enemy
of batteries, but it is most likely to go tango uniform on a cold day,
probably when you need it the most. That is also why the battery lasted
so long, it stays relatively cool away from engine heat in its hard to
access location. If you have a southern battery, you can also open it
to check/add water.
Unless you have a heated garage where you can work on it when it finally
dies or don't mind having a tow guy "work" on your car at an
inconvenient time, I'd recommend changing it now.
The power drain and severe voltage fluctuations that are causing your
electrical issues are not good for your electronics over time and
especially the main computers (PCM/BCM).
Costco sells Johnson Control's best traditional battery (aka Die Hard
Gold among other brands) for about $50 (Kirkland) and is well worth it.
Since your battery hasn't been removed in 11 years, expect a hassle
and badly corroded parts when removing the tie down bolts and electric
Is there actually a battery warning light on a 1999-2004 300m? Or are
you referring to the engine warning light?
I'm aware of that.
Presumably the car's "computer" (ignition-control or engine-control
module?) is always monitoring the voltage of the main power bus (any
wire that comes directly off the battery) and is monitoring this voltage
sufficiently fast enough to catch the deepest dip in the voltage that
happens during engine cranking - or perhaps immediately after cranking
when the user has turned the ignition key from start to run position.
I've previously stated that my factory-installed 5-disk CD changer
behaves strangely (like it was reset) during the most sluggish, coldest
starts must be an indication that it was exposed to an under-voltage
power condition, which should be trivial for the ECM to detect and
trigger a fault code - that is, if the designers of the ECM had the
foresight to program an algorythm for this condition.
I don't think I've ever actually seen the battery in my 300m (if it has
an eye, can it be seen from it's installation position?).
I bought a battery 3 or 4 years ago. I bought this battery primarily
to start and move a car in storage, and secondarily as a replacement for
the 11-year-old battery we are discussing now. Several times a year I
put that battery on a charger, but otherwise it's been sitting in
storage (at room temperature) for 99% of it's life so far. For the past
few weeks, I've kept that battery on the floor of my back seat, so if I
need a boost to start my car, I have what I believe to be a sufficiently
strong battery to use for a jump-start.
I've been making many short trips this past week, and I believe they are
not sufficient to allow the car's alternator to charge or keep this 11
year old battery at a sufficient state of charge. So I've connected the
battery charger to the battery while the battery is still connected
normally to the car's electrical system, but while the ignition is
turned to the full-off position.
I've noticed that the battery has more "pep" at starting the car the
last few times. I will continue to run the charger over-night on the
low-amp setting (trickle charge setting) and see how the battery
responds to this.
Yes, there is. It is an amber light in the shape of a battery. It
really monitors the charging system though, although it warns you that
the battery is probably going to be dead soon. The FSM lists all the
reasons that would cause the computer to illuminate it.
I'm sure it can and probably does, but storing a fault code for that
and/or turning a light on would probably cause a lot of false alarms and
trips ($$$) to the dealer for no real reason since the power can
fluctuate a lot normally.
Yes, it should be if you remove the air cleaning box on top of the
battery. (No tools required except maybe a screwdriver to loosen the
air intake clamp which makes it easier).
The condition is probably a result of the battery's losing ability to
hold a charge more than the distance traveled. Even a bad battery can
perk up temporarily when put on a charger.