PSA: Got a dead battery?

For many decades, the only electronics in cars were their radios, lights and ignition systems.  Then came power windows and locks, followed by fuel injection, which introduced computers to the automobile.  Then sensors galore, and with them, more computers.  Nowadays, satellite navigation, touch screens and high-powered sound systems are standard or optional on most vehicles.  With all the new electronic gizmos that automakers have added to their products, it’s no wonder that car batteries die quicker.  Not to mention motorized seats and mirrors.

With all of the electronics in cars these days, I am getting more and more questions of, “John, why doesn’t my car start after sitting for a week or so?”  The answer to this question lies in the car’s electrical system.  For those of us that have more than one car, the nicer car probably stays parked during foul weather or when driving it isn’t practical.  Anybody who owns a convertible which mostly sees weekend duty should be nodding their heads in recognition.  The people that own a weekend car may only drive their car a few thousand miles a year, mostly on the weekends.  That leaves an entire week between drives, or longer in some cases.

What does this do to the car?  Traditionally, not much.  After a couple of weeks, the tires may be slightly out of round, causing a rough ride for the first few miles until they warm up, but if you have a car with a lot of electronics built into it, you could be looking at a dead battery when you go to start up your “toy.”  This is because some of the electronics in newer cars run even when the car is turned off.  Things like the radio and clock, and perhaps even the GPS (Global Positioning Satellite) may run constantly.  These continuous drains on the battery can cause it not to start if not recharged on a regular basis.  In the past, headlights and interior lights were the most common reason a car’s battery died.

The solution to this problem is usually one of two things: you either hook up a battery tender, which feeds a little bit of electricity from your home to the car’s battery, keeping it topped off, or you have to drive it more often.  Battery tenders are easy to get, but may not be the solution some people want to hear – maybe it’s just not convenient for them, or they don’t have a garage to store the car and plug in the battery tender.  Driving also makes sure that any moving parts that need lubrication get that activity.  Even if you only have a few minutes to spare, backing out of your driveway, going around the block, and then parking the car for 20-30 minutes with the engine running, is enough to keep the tires from going out of round and make sure all the moving parts … well, move.  Running the engine after going around the block allows the car’s electrical system to recharge the battery.  Even if you can’t drive the car (say, it’s been a week, but there’s snow on the ground, and you don’t want to risk it), you can let the car sit in the driveway and run, to at least keep the battery charged up.

I have a close friend who owns a 2008 BMW 535xi, fitted with all the electronic bells and whistles BMW offers on a 5-Series car, and he averages less than 100 miles per week of driving.  Sometimes the car goes a week or more without being driven, at which point my friend notices the clock has reset itself.  A call to the BMW dealership revealed that the car shuts down “non essential” electronics when the battery’s charge gets below a certain point.  The clock is the most noticeable of these, but depending on charge, the radio settings and other user-configured electronics will revert to their factory defaults.  While the battery has enough power to start the engine, he has to reset the clock and other settings if the car isn’t driven for a week, which I think is ridiculous.  I gave him the solution I outlined above, so we’ll have to see how that works for him.

by John Suit

Battery Image Source: Send a Friend Auto Care