Looking for advice. Our son has a 2007 Mitsubishi 2007 XLS - have had for four years with no problems. Car is in great condition. One prior owner. Around 150,000 miles. Starting in September 2015 he has had to jump his car everyday to get the car to start. We had to buy him a portable jump because he was calling campus security every time he wanted to drive his car. He had a new battery put in in January 2015. He is away at college and the car may sit for a day or two before being driven. Then it is just driven short distances. When this problem started we had him get a new battery from a local car repair shop this September. That worked for about a week and then the everyday drain started again. I called our local Mitsubishi dealer and spoke to one of the service managers. He said the car needs to be driven at least 20 minutes to get the battery fully charged and suggested having him drive it for at least 20 minutes for a few days. That didn't work. So I have an appointment to have them take a look next week when he is home. The car should be able to sit for a day or two without having to be jumped. Once it starts it is fine. But if it sits overnight the battery is dead. So I am just wondering if anyone else has had this issue or what we should be having them look for. Thanks for any advice you can give.

 

I have had this happen in two previous vehicles.

For one of them, the issue was having some extra wires connected to the battery for trailer wiring (power brake) - once that was disconnected, the problem was solved. I bought it this way, and it was fine for a year or two, but then for some reason the same problem arose.

For the other, it was an alternator that went bad.

 

We thought it might be the alternator but the mechanic he took it to at college said it was fine. It may have gone bad since then so hopefully that will be the fix. But I should have mentioned whenever he is home for a weekend he never has that problem. The car starts right away. Getting home is a four hour drive each way and then he is in and out all weekend so maybe the battery doesn't completely get a chance to drain. Thank you for your suggestions. Will certainly ask them to check both out. We did buy the car with a pre-installed hitch.

 

If the alternator is bad it could stop running at any point... You can pretty easily check the voltage at the battery with a voltmeter to make sure it's charging while the car is running.

Any system in the car could have malfunctioned causing a current drain while the car is off.

The only way to find it is to hook an amp meter up and then start pulling fuses until the drain goes away.

If your battery is good and your charging system is working you should be able to let it sit for many days without problems.