If a battery drains while unhooked, it is either a bad battery or there is dirt or moisture between the terminals. Mix some baking soda with water. Clean the top of the battery with it. Don't let it pool.
Even while your car is off, your battery provides power to things like the clock, the radio, and the alarm system. These things shouldn't have a major impact on your battery. What may drain a car battery when it's off are things such as interior lights, door lights, or even bad relays.
Your car battery can only last so long before it fails when you're not driving because of key-off drain. Also known as parasitic drain, this occurs when a car's electrical system continues to draw power from the battery—despite the vehicle being shut off.
Using a test switch and digital ammeter is the simplest, most accurate way to measure parasitic drain directly. A test switch goes between the negative battery terminal and negative battery cable.
A corroded or defective alternator diode will faultily continue charging the circuit even when the car off. This, in turn, will drain your car battery and cause the car not to start.
No a burnt fuse can't cause battery drain issues. Some fuses don't get power until the circuit is turned on so don't be concerned about them. Has your battery been replaced or load tested to make sure it's good? A weak battery can make it seem like you have a draw.
Test the starter utilizing an amp gauge. The starter will draw a charge from the battery. If it's drawing too much, that's a clear indicator that's has failed. The vehicle may still start; however, it will continue to draw too much power and will drain the battery.
Some of the most common reasons for a car battery to die repeatedly include loose or corroded battery connections, persistent electrical drains, charging problems, constantly demanding more power than the alternator can provide, and even extreme weather.
The ignition relay is essentially an electrical device that works as a switch for the power to the ignition system. Its job is to make sure electricity flows from the battery to the different components that need power. A bad relay will drain your battery and make it difficult to start the ignition.
The short answer is: Yes, it can. It could also drain the battery even faster if you repeatedly try to start your car with a faulty starter. A faulty starter is also one of the leading causes of battery overcharging.
LEAVING YOUR KEY CLOSE TO YOUR CAR
Leaving your car key in your car overnight or even on a hook near the car is not recommended. If the fob is too close to your car, it can continue to communicate with it, which could drain the battery.
If your car charging system isn't working properly, your battery can drain itself even while you're driving. Most cars power their lights, radio, and other systems from the alternators which makes the battery drain worse if there's a charging problem.
No, it won't drain overnight if you disconnect the positive lead. However, it's very bad practice & can be dangerous, assuming the car is negative earth/ground. NB: Just about every car built since about 1965 is negative Earth. Disconnect the negative terminal.
Car suddenly stalls while operating: One of the most common symptoms of a failed ignition relay is a car that suddenly stalls while operating. If the ignition relay shorts, burns out, or otherwise fails while the engine is operating it will cut off power to the fuel pump and ignition system.
This can be caused by overcharging, undercharging, or leaving the battery in a discharged state for too long. A battery that doesn't hold a charge is frustrating and can happen for many reasons. It could be an issue with the batteries themselves or a problem with the charging system.
When you attempt to start the vehicle, is there a clicking sound, but it won't turn over? That may be a good sign. If a jump gets the car running, but won't turn over again once it's shut off, a dead battery is likely the cause.
An effective method to determine whether it's your battery or alternator that's gone bad is to connect jumper cables from a running vehicle's battery to yours. After a few moments, try starting your vehicle. Once it's started, remove the jumper cables — if your engine stalls, your alternator has probably gone bad.
If you hear a whine or the sound goes fuzzy when you hit the gas, your alternator is probably failing. If the vehicle won't crank or start but the headlights are still working, look to problems with the starter or other parts of the engine.
Faulty relay switches. According to YourMechanic.com, “If the relay shorts, it can leave power on to the computer, even when the vehicle is turned off. This will place a parasitic drain on the battery, which will eventually cause it to go dead.”
In some cases, you might experience what is known as a parasitic draw, also known as parasitic battery drain, which is when a continuous and abnormal discharge of power occurs, even after the engine is shut off. Walking out to your car ready to start it only to be greeted with a clicking noise can be frustrating.