Q: New battery goes dead overnight

asked by on September 07, 2017

I recently got a new alternator replaced in my vehicle, but every time I drive it and park it the next day I go out the car is completely dead. Before the alternator was fixed I replaced the battery. Could have that bad alternator affected that battery and I need to replace it with a new one?

My car has 54000 miles.
My car has an automatic transmission.

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If you have a new battery, you should be able to drive for a few hours and be able to restart the car a couple of dozen times even if the alternator is not working. So I suspect you have an electrical drain that is staying on when the car is shut off. It could be as simple as an interior door light that doesn’t go off, but it’s probably more complicated than that. Modern cars are always drawing on the battery when the car is off, just a few miliamps. It’s not enough to drain the battery overnight, but it can drain the battery if you don’t drive the car for a few weeks or more. If something has gone wrong, and the car has a significant drain, it can go down overnight. Finding that drain requires a technician who is familiar with the systems on your car. Contact YourMechanic to have a technician come out to your home or office to check out your Caravan and let you know why the battery is going dead.

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