Car Battery Goes Dead After a Few Days





Introduction: Car Battery Goes Dead After a Few Days

This is my 2012 Hyundai Sonata. I did not drive it for ten days. When I returned home, the battery was dead. I have never had that experience on any car ever I drove.

This Instructable applies to my car, but with all of the modern electronics running in the background on today's automobiles, your car may have this problem, too. This Instructable tells about the solution to my problem, but may be helpful with a similar problem on your car, too. 

Materials needed for this Instructable--none

  • Multi-meter with an ammeter scale capable of reading up to about three amps.
  • 8 mm socket wrench and ratchet
  • Spring clamp for connecting a small alligator clip to the battery post

Step 1: How Much Is the Current Draw?

I disconnected the negative (-) battery cable and connected my multi-meter between the cable and the battery post. (Check to be certain it is safe to do this on your car. I was reading the manual for another new vehicle and it seems some things need to be reset if the battery is ever disconnected.) The meter was set to measure DC amperes. Check the terminals on your meter to be certain you have the leads connected properly for the scale on the dial. The leads plug into the meter at different terminals for a current reading than they do for a voltage or a resistance reading.

With everything "off," the doors closed for a few minutes so all dome lights have gone "off," and the key removed; there is a current draw of 470 milliamps, or nearly half of an amp. At a recent visit to the nearest dealership for routine warranty service I asked about this. I was told that is normal. If I am concerned, I should connect a trickle charger when I will leave the car unattended for more than a week.  See the second photo. This is a battery conditioner we bought a few years ago for another purpose. I could mount it in the engine compartment and connect an extension cord to it when we will be gone for more than a week.

My question of the dealership was, "What do I do if I need to leave the car in an airport parking garage for a couple of weeks?" There are no electrical outlets in the parking stalls at any airport garage I know. 

Step 2: What the Dealership Did Not Tell Me

The dealership might have told me there is information in my owner's manual that advises me to pull a special fixture on the fuses, and that would reduce the current draw to a very low level. Yes, I should have read the entire manual after I bought the car, but it is hundreds of pages long. 

The graphic is a page from my owner's manual in the section on fuses. It describes a memory fuse that can be pulled when leaving the car unattended for long periods of time in order to avoid a dead battery. Even if I had read this, I am not sure I would have remembered it or that I would have made the connection in my mind. From doing searches on the Internet, particularly on an owner's forum, I suspect this information has escaped others, too. But, the search for a solution to my problem can be more complex and confusing than it would seem. Some have had the dead battery problem because of a bad cell in the battery, faulty battery cables, a bad diode in the alternator, or even a problem in the car's radio. A dead battery after a few days has been a problem on several makes of car, not just my 2012 Hyundai Sonata.

UPDATE: October 9, 2012-- A friend who owns a 2013 Sonata spoke with his dealer in a different state and city. He did not let the dealer know he is aware of the memory fuse. He asked about the battery going down in a short time. The dealer said new cars of all makes and models have so many electronics items running in the background, even when everything is "off," that the battery on newer cars will go down fairly quickly. When my friend asked what to do, the dealer advised buying a trickle charger. Then my friend asked what he should do if he needs to leave his car at an airport lot for a few weeks. He got only a blank stare from the dealer and no answer. Then my friend led the dealer a bit and asked if there would be any kind of fuse that could be pulled to reduce the current draw. The dealer said he did not know of any!

Step 3: Fuse Information With Photos

The photo shows how to remove the panel covering the memory fuse that needs to be deactivated when the car will be unattended for a longer period of time. Just lift the panel to remove it. It is on the left side of the dashboard between the steering column and the door.

Step 4: Find and Pull the Fuse

Two fuses are ganged together in a yellow plastic holder. You cannot see it while sitting in the driver's seat, but must kneel beside the car with the door open. However, you can locate the fuse holder from the driver's seat by touch without seeing it. Grasp the yellow fuse holder with a thumb and finger. Pull toward yourself. There will be a little click and the dome light will go "off." To restore, just press on the yellow fuse holder with your thumb and replace the fuse cover.

There are two fuses in this holder. To remove the holder from the car, squeeze it under the extensions you grasped on each side and pull. This releases two small catches. Each fuse can be removed separately from the yellow holder and replaced as necessary.

Step 5: Big Difference

Here you see the reading on my meter after pulling the memory fuse holder. It is only 40 milliamps. That is not enough to make my battery go dead, even if left unattended for weeks. 

Check the owner's manual on your car to see if it has a fuse like the one on my Hyundai Sonata, especially if you have had a dead battery problem after only a few days.



    • Pocket-Sized Contest

      Pocket-Sized Contest
    • Paper Contest 2018

      Paper Contest 2018
    • Trash to Treasure

      Trash to Treasure

    We have a be nice policy.
    Please be positive and constructive.




    thanks for the write up. An easy work around would be to connect a wire from one side of the female fuse connector, run it in series to a fuse holder (with fuse) then through a switch and back to the other end of the female fuse connector. By doing this, you can just turn the switch off to mimic pulling the fuse out. This is how I did my kill switch by bypassing the ignition fuse.


    I suspect Phil B got a high (470mA) reading for the battery drain in his 2012 Sonata because some or all of the car's electronics were still active because not everything was shut down, including locking of the doors and closing of the hood and trunk lid. With my 2009 Genesis, which is loaded with electronics, the ammeter readings after about two minutes alternated between 27mA and 16mA as the dash security light turned on and off. Not excessive, but I found that even this was problematic if the car was parked for more than a week. It's worse now that the battery's 8 years old and no longer takes a full charge.

    I don't drive the car often enough to keep the battery voltage up. I used the 30A Memory fuse regularly for a while, but started having reservations because the contact grooves in it were getting deeper with use and I was afraid it would fail (open circuit) causing the engine to cut out (can anyone confirm or refute this?) at a critical time. I'll either continue doing this, replacing the fuse with a new one periodically, use a battery charger, or, as another writer has suggested, install a switch in series with the fuse, which, if there's room, would be the best option.

    Update: I installed this switch, a 20A Digi-Key #CW100-ND, and repeated measurement of the battery drain. With the switch closed, the ammeter readings alternated between a base amount of 21 mA, jumping to 27mA-31mA with each flash of the dash security light. With the switch open, the base and peak amounts were 5.2mA and about 11mA, respectively. Opening the Memory fuse thus results in a reduction of about 16mA (75%) in only the base current drain. The rate of voltage decline in the battery was 0.03V/12hrs with the switch open and 0.13V/12hrs with the switch closed. At these rates my battery would probably be flat in 7 days and a little more that 2 days, respectively. For storage longer than a week, using a timer I'll trickle charge it nightly for 1-2 hours. Bill E, Sep26/17.

    we have a 2003 chevy trailblazer and we have recently gone through 2 sat in the driveway for no longer then 4 days without driving and we went out today to start it and its dead..before this we had it checked to see if the alternator was ok and was told that both battery and alternator were what could be pulling all the power from the battery while it sits

    I am not a mechanic. Chances are someone else has had your problem. I pieced together bits and pieces from posts by other people who had the problem. Check with your dealer to see if there is a technical service bulletin (TSB) on your problem.

    As for what could cause your problem, vibration while driving could wear the insulation on a wire thin so it leaks current. One Sonata model had a design flaw in the radio that caused a battery drain after the car gained some miles on the odometer.

    Hello car expert ..
    I accidentally left car lights on and i found after few hours m not able to start my car.. is der any solution i can do before father gets to knw about tat..?

    Find a friend who can lend you a battery charger for a car battery. Do some reading on how to connect and disconnect a battery charger safely. (Charging a battery creates hydrogen gas. Creating a spark near that can cause a violent very injurious explosion.) In a few hours it will be fine.

    It's sad that one has to resort to fixes for otherwise nice cars. More so because there isn't an excuse for it, other than shoddy engineering.

    I've owned the converters you tie to your battery to run small tools. They shut down when they take the battery voltage below a certain level, so they will not leave you stranded.

    These are not complex systems and could, easily and relatively cheaply, be incorporated into the electronics system, with a bypass to get the owner back on the road when the cut out kicked in.

    An old test for whether there is a drain on a vehicle battery, when you think everything is off, is to remove the negative cable and connect a twelve volt light between it and the negative battery terminal.

    If nothing is on, the light will remain off. If you turn on the parking lights or some other item, the light will light because the current has to flow through the light.

    Of course, clocks and radios of today are always draining the battery, but their load is light. Drains on the battery can even come from a filthy battery.

    I have a step van, which sits for long periods. Because of that, I put a battery shut off on it. Because it's an ugly beast from the git go, the cut out is on the dash (a LARGE red button available through Harbor Freight). Because it's convenient, it gets used.

    For a regular (nice) car, I could get one of the switches that mount at the battery.

    hey guys need a very big help here.
    My Hyundai accent also faces the same problem . i leave my car in the parking for 5 days and the battery dies, but when i disconnect the battery from the terminal and later after a week also it starts normally when i connect it back . Is it battery problem or anything drawing battery from the car?? Please help , i could save some money on this