Electrical diagnosis and repair at your location in DFW

Time, heat and vibration: what ends a battery's life

AAA says three things decide how long a car battery lasts: time, heat and vibration. AAA says the gradual wear that eventually leaves a battery unable to start an engine could take three to five years.

Heat speeds up wear. AAA contrasts cooler northern climates, where a battery may last five years or longer, with hot southern locales, where it will typically last approximately three years. Missing or loose hold-down hardware can significantly shorten battery life through vibration. AAA suggests testing the battery every year once it reaches its third year.

One click, rapid clicks, and a car that dies after a jump

AAA says rapid clicking when the key is turned generally indicates a battery issue, while a single click with bright dashboard lights often means a bad starter motor. If the car starts with a jump but dies again after a short drive, the alternator is likely not recharging the battery.

Before an alternator is blamed, APEX Tech Nation, a technician-training site, says to check the drive belt and then the large output wire at the alternator, where the nut can work loose from vibration and the terminal can corrode. It gives 13.5 to 14.7 volts at the battery with the engine running as the range for a conventional charging system, and says that on such a system below 13 volts with the engine running confirms undercharging. It adds that these are general ranges and that the manufacturer's data for the exact vehicle governs.

APEX says most vehicles built after 2010 use smart charging, where the powertrain control module (PCM) sets the target. Such an alternator may put out 12.8 volts on steady highway cruise if the battery is full and 14.8 volts during deceleration, so one reading can mislead. A stored code such as P0562, voltage below threshold, is one place a scan can point.

Parasitic drain: Optima's rule of thumb is 25 milliamps acceptable, over 100 a problem

With the key off, a modern car still draws some current. Optima Batteries lists memory seats, mirrors, radio presets, satellite radio, GPS and wifi as loads that have raised key-off demand, and agrees that an 85 milliamp draw is not unusual on newer vehicles. Its guidance is that about 25 milliamps is acceptable and anything over 100 milliamps indicates an electrical issue. The manufacturer's specification for the vehicle governs.

Optima says a battery should not drop below 12.4 volts, because below that sulfation begins to diminish capacity and performance. Its example: an 85 milliamp draw on a single 50 amp-hour battery would completely discharge a full battery in just over three weeks, and sooner if the battery is not fully charged or the climate is hot. A car would stop starting well before the battery was empty, since Optima says the battery needs to be well above zero percent charge to start the vehicle.

Battery registration on BMW, Mini, Volkswagen, Audi and some other makes

Midtronics describes battery registration as a programming procedure that tells the electrical system a new battery is installed, so charging parameters reset for a healthy battery. It says the requirement has mostly applied to BMW, Mini, Volkswagen and Audi, that it will likely extend to other vehicles, and that cars with an intelligent battery sensor will likely need it. Midtronics also names Mercedes-Benz, Porsche and Volvo and says the list is growing. Skipping registration can mean overcharging or undercharging, limp mode, a no-start, or a start-stop system that might not engage. Midtronics says registration needs a scan tool that supports the specific vehicle, that standard OBD-II code readers typically do not support it, and that the automaker's service information should be checked.

Type matters too. AAA recommends the replacement match the original, conventional or AGM, because automakers optimize charging systems for the type. AAA says the group number sets size, hold-down and terminal position.

Jump-starting: the clamp order AAA uses, and when to skip it

AAA says not to jump a battery that is cracked, bulging or smells of rotten eggs, and to confirm both vehicles use 12-volt batteries. Its order is red clamp to the dead battery's positive terminal, the other red to the donor's positive, one black to the donor's negative, and the last black to clean, unpainted metal on the dead car, such as a thick bolt on the engine block, so the final spark stays away from the battery. Both ignitions stay off while connecting. AAA also says to wear safety glasses, remove metal jewelry, set the parking brake, and disconnect the clamps in the exact reverse order. Follow AAA's full steps rather than this summary.

AAA warns that most hybrid and electric vehicles have complex electronics that can be destroyed by jump-starting another car. AAA makes that point in the part of its equipment list about choosing a donor car, so do not use one as the donor, and check the owner's manual before connecting cables to any vehicle you are unsure about.

AAA says a continuous drive of 20 to 30 minutes afterward is usually enough to recharge, with the air conditioner and rear defroster off, and that a short drive will not save an old battery. AAA calls a poor connection the most common reason a jump fails, since even a thin layer of whitish-blue terminal corrosion can stop electricity.

The old battery: what Texas asks of the seller

Texas Health and Safety Code Section 361.452 says a person selling lead-acid batteries at retail must accept from each customer, if offered, at least one but not more than three lead-acid batteries for recycling, and post a notice that it is illegal to discard or improperly dispose of a motor-vehicle battery. Section 361.138 requires dealers who must collect the Texas battery sales fee to list it as a separate item on the invoice.

Battery Council International, an industry group, says 98 percent of lead batteries are recycled and that a new lead battery is typically made of 80 percent recycled material. Confirm current rules with the TCEQ or the Texas Comptroller.