Skip the auto shop - Our mechanics make house calls

Q: The car won't start after battery was overcharged. 2001 Hyundai XG300

asked by on

I had the battery in my car overcharged by the alternator. It was charging about two hours longer when I stopped it. After waiting for a while, I started it and had the negative cable disconnected. At that point, the AC, dashboard lights and all other interior and exterior lights flashed and the car cut off completely. The battery had 12.8 volts. So, I had the cable replaced along with the 30 amp starter fuse and the 120 amp fusible link. Then, I attempted to start the car again but the car was still completely unresponsive. What happened here? What should I do?

Hello there. It sounds like you have a cloud of things going on with your Hyundai XG300. If the alternator is overcharging the battery, then there is a good chance the alternator has failed. Most of the time, this is caused by a faulty voltage regulator that is internal to the alternator and must be replaced together. Once the alternator has been replaced, the battery should charge at a normal voltage.

If the alternator either over or under charges the battery it often becomes damaged. In many cases, the alternator and battery are replaced together due to the alternator causing the battery to fail. A qualified technician, such as one from YourMechanic, will load test the battery to check its condition and perform any other tests to diagnose this starting issue.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • The car won't start after battery was overcharged. 2001 Hyundai XG300

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Battery drained in under 24 hours

This may be caused by many possible issues such as a short in the electrical system, a bad grounding connection, a faulty alternator, or a weak battery. Without further details, this may be difficult to diagnose. I would recommend...

Q: Radiator smoking

There are a number of reasons why your car may be overheating. number one is a possible coolant leak. If a hose or a radiator or other part of the cooling system is leaking, and the coolant is not replenished,...

Q: Headlights dim when revs drop while driving

Check the battery and have the alternator load tested. A lot of times it is as simple as you needing a new battery or an alternator. You can get the car load tested or try or test the alternator yourself....

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.