Q: New batt New alt batt voltage still drops?

asked by on July 20, 2017

ok i get in my car to leave work and see the batt light is on so i check the information center on the dash and my batt reads 12.1v as i continue to drive i notice its dropping so i stop at pepbays on my way home (a half hr from my job) and by the time i get there its at 10.5v and the car has went in to (battery saving mode) pep boys checks my batt tell me its bad i buy a new one start the car to go home dash reads 12.8v within the 5-10min drive home by the time i get there its on 11.7 v so i go to autozone to get an alternator another 10min there 10min back and by the time i get jome 10.9v i put in the alt start car this morn drive to work and by the time i get here the batt is at 10.4 and car wont start back up i have BRAND NEW battery out of the car on a charger now

My car has 121000 miles.
My car has an automatic transmission.

It’s possible that the charging circuit is not properly connected (wiring, fuse, or ground fault) or there is some large excess current draw in your car’s electrical system. Basically, if the battery is new and fully charged and charging system output has been measured and is within specifications, the only reason a battery will discharge is if the car sits for a long period of time (batteries will self-discharge even if not used) or if there are parasitic (excess) loads on any of the car’s electrical circuits. If there is excess current flow that is slowly draining the battery, a Mechanic would use an ammeter to test all of the various circuits until the faulty circuit is found. Then that circuit is traced to find the fault and repair it. If you want this issue you are having diagnosed and repaired by a certified Mechanic, dispatched by YourMechanic right to your location, please request an electrical diagnostic and the responding certified mechanic will get this resolved. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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