Today’s cars are loaded with electronics. That’s not news. There are GPS systems, clocks and infotainment, countless sensors, anti-theft systems, powertrain functions (from engine to wheels), smart brakes, data links, and even “polling” which reports vehicle-condition, to cite just a few items. Some estimates are there are at least 100 electronic functions in a typical car, each with its own processor. You’d like to think that when the car is “off,” these circuits are also off as well.
Except they aren’t, of course. Even in the so-called off state, many of these circuits are in standby, quiescent, or sleep mode — call it what you wish — and all need a little bit of current from the battery so they can do whatever they are supposed to do when the vehicle is presumed to be off. Each one has a very modest drain, usually around a milliamp — hence the term “vampire” drain — but those milliamps add up to a significant, continuous drain on the battery.
And that’s the problem. As a recent article “Long-Term Parking Can Kill Your Battery” in The Wall Street Journal noted, the problem is very real and — ironically — it’s worse with high-end cars (including the all-electric Tesla) as they have more features. Apparently, it’s not unusual for these cars to “die” when they are parked for even a few days, which can happen at home or the airport long-term parking lot.
What’s worse, when the battery drops below a certain low level, you can’t even jump-start it, as the sophisticated battery-management function in the car decides the battery is “dead” and resembles a brick, or is missing. Then, the only option is to have the car towed for a battery replacement.
This problem is not anecdotal. The article cites some figures, and also quotes dealer-service and car-fleet managers who give estimates of between three and seven days “life expectancy” for many of these cars — and that’s assuming the battery was in good shape. If the battery is older and holds less charge, or if it is much colder or warmer than normal, then you have even less time.