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I have a Prius 2004 bought used 2 years ago. The 12v battery keeps dying. I changed the battery twice, with the last one installed in a few weeks ago, and since then the most I have left the car parked without driving it has been around a week. Yet this last battery is already weak and failed me three times. At this point there is no redeeming chance for it I suppose.

Any tips appreciated on what could be happening. My mechanic skills are limited but I should be able to follow instructions.

Thank you.

Pᴀᴜʟsᴛᴇʀ2
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Eric Anonymous
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1 Answers1

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Either something is draining the battery while the vehicle is parked, or it's not being charged back up properly while being driven.

To check the charging, use a multimeter set to 20 volts. Check the voltage between the battery posts while the vehicle is running. You should be seeing something between about 13.5 and 14.5. You may need to rev the engine up a few thousand RPMs to get the full charging voltage.

http://www.aa1car.com/library/charging_checks.htm

To check for a parasitic drain, you can turn a multimeter to amperage (start high, work your way down) and connect it between the positive post on the battery and the positive cable. Anything more than about fifty milliamps is likely a problem.

http://www.popularmechanics.com/cars/technology/how-to/a5859/how-to-stop-car-battery-drains/

raydowe
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