Car battery draining overnight can be very annoying and exhausting as well. It is more devastating especially if you have tight morning errands and you have to jumpstart your car. Bothering neighbors or other car owners is very boring.
It is important to find out and understand the root cause of the problem of the battery so that you can keep the jumpstarting cables away. The big question is why is the car battery draining overnight?
Well, from my experience as an automotive technician (having worked with various types of car batteries) and extensive research, I have come across various causes and solutions which am going to outline below.
You can also read our other guide: Top car battery brands that perform well
What Causes Car Battery Draining Overnight
Bad alternator
If your alternator is not working properly, it can mess you big. You can find your car failing to start despite doing a drive. Obviously, the alternator charges the battery to charge when the engine is started and when driving. If it is not working then it won’t charge your battery enough.
Old battery
Everything that has a start has an end. Your battery can serve you anywhere from 3- 8 years but again the life span shortens if the car is being used regularly. Other factors such as high temperatures can also reduce its durability.
Most regular batteries work efficiently for about 3 years before being problematic. However, if your car battery is new and still draining overnight, it is time to look at the other possible causes.
Whenever the battery gets old and starts being problematic, the only solution is to buy another one because after jumpstarting it will still not hold charge. This usually happens because of the degradation of the battery cells.
Parasitic draw
If you have been wondering, what can drain a car battery when the car is off? Parasitic draw is usually one of the main culprits.
This happens when an electric current continues flowing in your vehicle even after turning off the ignition. This pulls the stored energy in the battery.
This happens when electronic systems in your car such as the alarm, or radio or internal clock drain energy from the battery including when the car is turned off. These electronics get power from the battery and when the alternator is off definitely the battery won’t recharge.
Having the radio on while driving is reasonable since the battery gets charged from the alternator and thus it can’t drain easily unlike during the night when it is off.
Common causes of the parasitic drain are malfunctioning trunk lights, headlights, glove box lights, radio, or fans that do not turn off when the car ignition is switched off. This leads to the car battery draining overnight.
Corroded terminals
Corroded terminals are very easy to notice and you can tell by just seeing them. For a fact, they are poor conductors of electricity. Mostly it happens on the negative terminals which means the battery was undercharged.
If it happens on the positive terminals it means overcharged battery which rarely occurs. Corroded terminals create a closed circuit and cause current flow resistance and hence affecting the starting of the engine.
You can read our guide here on how to clean corroded car battery terminals.
High temperatures
Since batteries run on electrolyte liquid which provides charge to the battery. During hot weather conditions, it may evaporate and reduce its power energy which now makes the car not start.
This mainly applies to flooded batteries and rarely on Absorbent Glass Matt (AGM) batteries.
Leaving headlights on
We are all humans and there are times we are super beat. You tend to forget to switch off the headlights or any other interior lights on.
Other cars automatically turn them off but others don’t and if yours is such a car, it might not start the next morning. Surprisingly in the morning, you won’t notice that you left them on because you will find them off after they drained your battery.
Short Trips
A car battery is by default charged by an alternator when the car engine is on. If you make short trips and distances the battery will not charge enough and the charge will go low more because starting a vehicle uses a lot of charge .
The battery life can shorten if you have short trips most of the time especially if it is an old battery. Some other car batteries die after sitting for a few days.
Short trips is usually what causes a car battery to die quickly because the battery is never charged to an appropriate level. Batteries that are not deep cycle also do not tolerate extreme discharges and charges.
If your car is not a daily drive or you like using car accessories like the music system, consider going for a deep cycle. Optima batteries have special deep cycle batteries that handle this well.
This can affect a person who works from home and the only time you are out is during the weekend. That time you decide to go out with family, friends or alone and the battery fails you.
Have you ever asked yourself why your car battery dies if not driven for 3 days? That is if it has ever happened to you. The battery can be having a problem with a parasitic drain or as it ages this issue grows up.
The important thing is to conduct a parasitic test if you think it could be the electronics draining the charge. Otherwise, there are rare cases of a new or good battery dying after sitting for such days without the vehicle being driven.
How Do You Perform A Car Battery Drain Test?
1. Turn off all electronics
The first step is to make sure that all car electronics are turned off as well as any cables such as chargers are disconnected. Your vehicle too should be turned off.
2. Connect the battery charger
Hook the car charger on the battery and make sure it is fully charged. Use a multimeter to check whether it is fully charged to at least read 12.6 volts which is the average for most car batteries.
Your multimeter should at least have Amp (DC) reading.
3. Attach the multimeter cables on the terminals
Using a 10mm wrench unbolt the terminal showing the minus sign which means it is the negative terminal. There are two cables; the negative and the positive but using the negative is much safer than the positive.
You will not experience electrical shorts with the negative cable.
Now set up the multimeter and select the Amps input. Make sure both black and red wire are well attached to the common ground and to the highest Amp input which is normally 20A respectively.
On the multimeter, there is a diagram showing you where to place the leads, the red wire should be placed on the end of the negative cable terminal through the metal circle and touch the black lead to the negative terminal. You can use clamps to secure the leads on the terminals and wire.
4. Check on the multimeter readings
The readings in Amp will start displaying on the multimeter. If it reads more than 50 milliamps then it means it has a parasitic drain. A battery that is well-doing should have a reading between 20- 50 milliamps.
5. Remove and replace the fuses
The next step is to remove the fuses one at a time you can use pliers of fuser puller. Remember to place them back nicely each on its position.
Start with the smaller fuses with fewer milliamps to the highest until the milliamps start to drop. In this stage, it is is usually faster with a helper who can help you check on the multimeter as you remove the fuses.
If you are alone you can place the multimeter on the windshield facing down so that you can read and do both at the same time. Once you get the affected fuse circuit, it can the interior lamps relay or any electrical device circuit among other circuits replace it or them with another and watch whether the Amps will drop.
5. Disconnect the multimeter
The last step is now disconnecting the multimeter and reconnecting the negative battery cable back. The parasitic problem is now sorted and you have come up with the car battery drain solution.
There are a few tips you can use to prevent your battery from draining overnight and you can rely on them. Here entails some of them.
Tips For Preventing Car Battery Drain
- Uninstall all unnecessary accessories that use power such as dashcams if not in use
- Drive for at least a couple of hours to allow your alternator to charge the car battery fully
- Avoid short trips, especially if your car battery is old and has problems
- Make sure that the headlights are turned off whiling parking the car at night
- Try and exchange vehicles if you have more than two to avoid finding car battery dead after sitting for 5 days or more
- Clean the corroded terminals of your car battery
- During hot temperatures prefer parking under shades, if possible, to prevent exposure from the sun]
Closing Remarks
With all that said we are now aware of what causes car battery draining overnight and some other issues related to battery drain. A car battery can give you a rough time and fail to enjoy the essence of having a vehicle.
If you notice problems with battery drain it is right for it to be solved and conducting parasitic drain test is usually a good starting point. This test is particularly important if the car keeps dying yet the battery and alternator are good.
- Best Solar Wireless Backup Cameras - May 15, 2024
- How to Clean Fabric Car Seats (Remove All Stains at Home) - May 6, 2024
- Top 5 Best Engine Oil Additives for Noise (Quiet Your Vehicle) - May 3, 2024
1 thought on “Why Your Car Battery Keeps Draining Overnight (Causes & Solutions)”