Most drivers know that their car battery is constantly being charged while driving; however, some individuals wonder if their battery is also receiving charging while sitting idle in park mode or idle mode?
Most cars feature an alternator to recharge the battery while the engine is running, typically driven by a serpentine belt that spins along with the engine’s rotation.
Idle Speed
Idle speed refers to the rate at which your engine’s crankshaft spins, moving your serpentine belt and powering an alternator that charges your battery. Even though your belt turns faster while driving, its voltage production remains the same since your ECU regulates it with equal care during idle speeds and driving conditions.
Your car’s alternator is at the core of its electrical systems, so it is vital that it has plenty of power to recharge the battery when your vehicle idles. A crankshaft turning at least 1000 RPM should generate sufficient electricity to replenish its charge to charge your battery when idled.
Newer vehicles often contain components or systems that restrict how much energy can be delivered from the alternator when driving idling, restricting how quickly its charge reaches the battery and thus lengthening its recovery from prolonged idling. This can leave it longer for your battery to recover from prolonged use of idling.
Cold temperatures can slow the charge rate of your battery significantly, particularly during Winter. These low temperatures prevent heat from building up as quickly and thus the charge slows significantly more slowly.
An automobile’s idling speed can vary depending on a number of factors, such as its battery age and number of short trips taken consecutively or the amount of time your vehicle has been sitting parked; however, one major contributor is how well its engine runs.
Idle speed of a car depends on airflow to its engine. This airflow can be affected by various factors, including vacuum leaks in its intake system; such as worn gaskets or damaged head gaskets that cause leakage.
Vacuum leaks can sometimes cause your engine to have an irregular idle, which is most commonly found on older vehicles but more commonly seen among newer models as well.
If your car’s idle speed is less than smooth, there may be an issue with vacuum leaks in its engine or an electronic throttle plate that needs attention. As these repairs can be costly to implement on their own, it is advisable to visit an auto shop immediately.
Battery Voltage
Battery voltage of your car is an integral component of maintaining its performance and can reveal whether or not a new battery needs to be purchased.
As the voltage of a battery changes as it’s charged and discharged, it is wise to perform periodic voltage checks with either a simple battery monitor or multimeter.
Voltage refers to the difference in potential between circuit terminals. When voltage levels are high, more power can be drawn from batteries while when voltage falls, you can draw less electricity out.
Use a handheld multimeter from most home improvement stores to measure the voltage of your battery, connecting its positive lead to its positive terminal and negative lead to its negative terminal.
Your meter may feature several settings for different voltage levels, but for the most accurate results use direct current (DC). This is the most precise way of gauging battery voltage.
At its optimal charge state, a fully charged battery should have approximately 12.6 volts; any drop below this value could lead to irreparable sulfation and damage of its cells.
If your battery reading is lower than this threshold, use a battery charger or take it for a drive. Also check to see if the alternator’s output has increased above average; otherwise this could indicate either an issue with its internal mechanism or wiring problems.
Another key step when purchasing a battery is checking its cold cranking amps (CCA). This measurement shows how much power can be provided briefly even in low temperatures.
A quality battery should provide enough juice to start your vehicle even on extremely cold mornings; however, its performance can differ depending on the make and model of car you have.
Ideally, batteries should have between 13.5-14.7 volts when starting their engine; this allows it to turn over. If yours are reading lower than this mark, replacement may be in order.
Alternator Voltage
Car batteries serve a vital purpose: when your engine isn’t running, they provide power to all the electronic devices on board and charge the battery up. As soon as it does, however, an alternator takes over to provide voltage to recharge it as well as supply your car’s electronics with electricity they require for functioning properly.
Your car’s alternator should provide between 13.8 to 14.2 volts when idle with all accessories and lights off, which may seem lower than what most cars achieve during high engine revs but is an acceptable and safe threshold to keep its battery charged when not running.
If your battery isn’t receiving sufficient voltage to fully charge, this could indicate that your alternator is malfunctioning or something else in its charging circuit is amiss. A low reading could also signal poor connections or wiring problems within its circuit.
An alternator’s diodes convert alternating current (AC) electricity to direct current (DC), so any failure could cause your battery to overcharge or undercharge and eventually lead to overheating alternator. A malfunctioning diode could cause your battery to overcharge or undercharge and even overheating of the alternator itself.
Use a multimeter to assess your alternator by measuring voltage across your car’s battery. A multimeter will produce both AC and DC readings that you can use to assess whether or not the alternator is functioning as it should or producing intermediate voltage levels.
A reliable way of testing alternator voltage is connecting the multimeter’s red probe directly to the battery’s positive (B+) terminal and black probe directly to its negative (GND) terminal, using its COM socket for measuring voltage, resistance and continuity measurements.
If the vehicle’s idle voltage falls below 14 volts, it may be time for an alternator replacement. Should this occur, seek professional diagnosis and repairs of your alternator as soon as possible.
Battery Current
If you own an older vehicle, charging its battery while it idles should not present too many difficulties. But newer cars may present additional obstacles; many now come equipped with sophisticated charging systems designed to limit or even mitigate how much energy the alternator puts out when your engine is idle.
Idle charging is essential for maintaining the health and lifespan of your battery and car. Without enough current flowing through, your battery may gradually overheat and ultimately die, shortening its lifespan significantly.
Thermal runaway can cause your battery to quickly drain in as little as an hour or two. To prevent this from happening, always maintain at least 12.6V charging voltage when charging the battery.
There are three stages to the charge process for batteries. They include constant-current charging (usually lasting 5-8 hours), topping charging and absorption charging. For constant-current charges, you must charge to 70 percent before moving onto topping or absorption charges.
After 7-10 hours, the charger switches to a topping charge, which lasts 7-10 more hours and ensures optimal battery health by stimulating its chemistry and dissolving sulfate deposits that could erode away at capacity over time.
During absorption charge, current drops to less than 0.01xC amps (1 percent of rated capacity). Following that step, the charger switches to its float voltage setting ranging between 2.25 and 2.30V/cell. Trickle charging is a form of battery self-discharge, occurring when your battery becomes detached from its charging source. Once voltage reaches this threshold level, current will decrease below 0.01xC amps and you may disconnect your charger. Once this step is completed, simply put your battery back into your car and it will begin charging again. This process should be repeated daily throughout its lifespan for maximum effectiveness in keeping batteries healthy – particularly important if living in cold climates where deep-discharged batteries may freeze over.