Car Battery Goes Dead After a Few Days





Introduction: Car Battery Goes Dead After a Few Days

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...
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.



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    I'm at my wit's end with a problem with my 1998 New Beetle, which has steadily gotten worse. I replaced the battery, I've spent hundreds of dollars on mechanics trying to figure out where the electrical problem is, all with no solution.

    I bought a trickle charger and hooked it up when I didn't plan to go anywhere - didn't help: even connected to a trickle charger, it just one day wouldn't start. I thought maybe I should just drive it everyday (I'm retired). So I tried that, but it changed nothing. Even after driving the car for 5 days in a row, I went to start it, and it wouldn't start.

    It doesn't seem as though the battery has gone suddenly dead; when someone gives it a jump start, it starts up again right away, without any time needed to build a charge. I can't see any pattern at all to what's happening, and it's making me crazy.

    1 reply

    Thank you for your comment. I am not a professional mechanic and have never owned a VW of any kind. I empathize with you in the problems you are having.

    I did a little cursory reading sbout electrical problems on the 1998 Beetle. Melted fuses and wiring harnesses, and outright fires, are not infrequent in the complaints. It seems an early sign of problems to come involves a lack of response from the heater/AC fan control. (The fan blows at the #2 setting no matter where the knob is set.) Some had the engine die in traffic, or the horn began to blow during the night with no known stimulus. I did not find your exact problem.

    The melted fuses and wiring harnesses suggests a heavy unusual current draw. That could also fit with your drained battery. My first thought is something simple, like the wiring crosses over a rough metal edge at a body seam and eventually wears through the insulation to cause an electrical short.

    In step #1 of this Instructable I described how to use an Ammeter to check current draw in a circuit. If you do not have a digital multimeter, Harbor Freight has one for around $5 that is often free with one of their ubiquitous coupons from the Sunday paper or an advertisement in a magazine and a small purchase. Start with the 10 Amp. range just to be safe and work back to the milliamps. ranges to avoid blowing a fuse inside the meter. (I had to go to Amazon to find replacement fuses. They are an odd size.)

    I would want to know the current draw when the car is parked by the curb, and then with the engine running. Is it higher than 50 to 100 milliamps when nothing is running? If so, I would pull a fuse and check the current draw. Replace the fuse and pull another. You are trying to determine which system has the excessive current draw. Then follow the wires for that system as best you can with your hand looking for any signs insulation is worn or frayed. (If you cannot follow the wire various places, try disconnecting it between the battery and where the wire becomes inaccessible to your reach.

    Ockam's Razor says the simplest explanation is usually the best. The problem could be a component failure, but is more likely to be something simple, like worn insulation.

    This is a tedious process, but it may eliminate a possible cause, which advances the inquiry.

    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

    2 replies

    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..?

    1 reply

    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

    3 replies

    I suggest you download a PDF copy of your car's manual. Then search it for "fuse" or "memory fuse" or "battery." See if there is a discussion about disconnecting the electronics to avoid running the battery down after a period of non-use. Be sure to read my Instuctable carefully, especially if your car has a memory fuse.

    To add to my point, i think there is problem with my head light, the head light indicator in the meter reflects ON when i switch off my car, do you think the small indicator light would be problem to drain my battery?

    The next time you take your car in for warranty service, ask for a check of the electrical system. The dealer did one for me at no cost. That is a starting point. Have you tested the current draw on your battery as I showed in this Instructable?

    well done instructable! As always hyundai has some of the overall worst engineering when it comes to vehicles. I've had some challenges with a Trajet and I wonder if those so called engineers had an ounce of common sense.

    I use a small solar charger avail for this purpose from Harbor Freight. Sits in the dash & plugs into the cigarette lighter (which depending on the vehicle, may need to be modified at the fusebox as it must remain "hot" with the ignition off or the charger won't work). Cost for the charger was about $15, perhaps less if you sign up for HF's email coupons (which often beat the sale prices in the flyers). Totally solved my battery going dead - also prolongs the battery's life. Had to get another charger recently though, after an extremely hot day on the dash and with the sunshades behind it - the frame melted. I bought my original charger perhaps 10yrs ago, hopefully the ones they are selling now won't melt in extremely hot weather. If the problem happens again, I might just leave the panel propped on the passenger seat where it should remain a bit cooler

    Solar cells work great and are very well made. Put one on in your windshield facing th sun for a few hours connected to your battery been working for a long long time. Never a problem.

    1 reply

    My car is not exposed to the sun when I leave it.

    Solar cells work great and are very well made. Put one on in your windshield facing th sun for a few hours connected to your battery been working for a long long time. Never a problem.