My four year-old battery died in my car. I replaced it with a new battery and a few days later, it was dead. None of the lights work and I can't find any reason why it would be drained.
There is most likely an electrical component that has failed, causing the battery to drain. These can be very tricky to diagnose. Basically, you need to be able to measure how much current is being drawn from the battery when the car is at rest, and slowly disconnect components one by one until there is no more current being drawn. Once you find the component that drops the current draw, you have found the problem. I would ask for help from one of the mechanics at YourMechanic to perform this test on your electrical components to see what is causing your battery to die.
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