I drive a 1995 Mercury Cougar with 109,000 miles. I bought a O’Riley Automoative battery with a 7 year warranty 11 months ago. After I initially installed the battery, after 2 weeks the battery was drained. This 2 weeks includes driving and not driving the car. I will charge the battery backup with a battery charger and 2 weeks later, the battery is dead. This is the second time I’ve bought a battery for the same car, and the same issue happens. I have had to charge this battery at least 10 times in the last 11 months. After 6 months of this, the 2 weeks time period shortened to just 4 days with battery power until it is drained.
I am trying to figure out what in my car is draining the battery. The car doesn’t have to be on for the battery to run out.
You have a “parasitic draw” or “parasitic drain”, meaning that an as-yet undetermined component is drawing power even when the car is turned off. Here is a good video on how to find it:
Look at the obvious stuff, after you turn the car off are there any lights that stay on? I have seen many parasitic draws, and a few examples are glove box light not turning off, trunk or hood light not turning off, even an intermittent brake light or radio not turning off, start simple and work your way up. Note after many drains and dead batteries your battery may need replacement, as dead battery is a battery killer!
It is also possible your alternator is on the fritz. Maybe some diodes are out (which can lead to parasitic current drains too). Have you engaged in jump starting other cars with this car, or had this car jump started? Sometimes jump starting can damage the alternator diodes. The alternator should be outputtting 14 -15 volts when you first start the engine. Ask your mechanic to confirm this.
It’s possible the new battery is bad from the get go, but unlikely. The first thing I’d do probably, is recharge the battery, then I’d take the car to one of those retail auto parts places that will test the battery and charging system for free. Best of luck.
I agree with GeorgeSanJose. I just had some charging problems with my Mercury Mariner. Took it to O’Reilly’s (auto parts store) and they did a free test for me. I was just going to buy a battery but then test showed that my alternator was running very weak. That will drain and kill a battery over time. So see if you can get a free test done that will check the alternator.
Also - if you have to replace that alternator yourself you might be in trouble. I was complaining about the accessibility of the alternator in my Mariner and the guy behind the counter said that the worst alternator replacement he ever did was on a Cougar. Not kidding!
