Mysterious Battery Drain

I purchased a battery about 9 months ago to replace a battery that was damaged and no longer holding a charge. Several times since then, if I let the car sit for more than a day and a half to two days, there’s not enough charge left in the battery to start the car. I’ve taken the car back to where I bought the battery and to the local dealership, and both have told me that the battery’s fine and holds its charge and that the electrical system is OK. There are no aftermarket items on the car, and I’m doing my best to make sure nothing in the car’s been left on after I park, including the radio and lights.

I like my car, but I really don’t want to drive it every day to keep the battery charged! Any suggestions?

Buy or borrow a amp meter (get one that can measure small currents) and measure the load on that battery. Remember modern cars tend to have complex electrical systems and it may start using more current after say 10 minutes or maybe even longer.

Good Luck

Do you want us to fix your car, or do you want to fix it yourself, or do you want us to advise you to take it to another repair shop? Which?

I think that Joseph meant to write that modern cars tend to use less current over time. As various processors in modules are idle, they go to sleep. Opening a door can wake some things up. Do a google search for “parasitic load test” to find out how to do it.

Here is a link you can use for reference if you want to try and fix the trouble yourself.

I’m not very good with cars beyond routine maintenance - if it’s something simple to test and fix, I’m open to suggestions, but otherwise advice on what I should be telling the mechanic - dealer or otherwise - to look for is greatly appreciated.

Finding a battery drain takes some skill and knowledge of electric circuits, and use of a multimeter. So far, the battery installer, and the dealer aren’t qualified. You’ll have to ask around, check around, for a qualified mechanic / shop. This type of problem is automotive electrics 101 (or, 102 at the most).