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Parked the car in the driveway, the battery had drained?

Tiny
PIGFEED
  • MEMBER
  • 2021 HYUNDAI SONATA HYBRID
  • TURBO
  • 91,121 MILES
Tuesday, I drove home, 58 highway miles. Parked the car in the driveway. Wednesday, the battery had drained.

AAA opened the car door and pushed the 12V reset. The car jump-started itself.

The hybrid system was listed as about 60% charged.

I drove it to the Hyundai dealer. They checked the battery and said it was 30% charged when they tested it. They fully charged it.

So, do these cars have voltage regulators? Could the generator be going?

Shouldn't a 50-mile highway ride be sufficient to charge the battery?
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Thursday, September 22nd, 2022 AT 6:31 AM

6 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,940 POSTS
In the fuse panel on the left side of the dash there are two fuses that need to be checked, Module HEV and Module 1 both are 7.5 amps. The battery is charged by the low voltage converter which is inside the hybrid power control unit. If the fuses are okay, it sounds like you have a bad 12 battery. Here are the hybrid battery charging wiring diagrams so you can see how the system works and I have included a guide to help you test the fuses. Also, I found the instructions on how to change the battery out with the fuse locations as well.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

I don't recommend a non-service professional to change this battery out but I want you to see what needs to be done to fix the car, so you know what you are in for with the repair. Check out the images (below). Please let us know what you find. We are interested to see what it is.
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Thursday, September 22nd, 2022 AT 11:04 AM
Tiny
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Module 1 shows up on the schematic. Module HEV. Does not.
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Thursday, September 22nd, 2022 AT 2:08 PM
Tiny
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The car doesn't have a key. It has only a fob. I cannot turn on just the electrical circuit.
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Thursday, September 22nd, 2022 AT 2:14 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,940 POSTS
When you say the Module HEV fuse does not do you mean the fuse is not there? Is there a place where the fuse can be installed? Can you please upload an image? Also, we should do a CAN scan which is easy, you can get a CAN scanner (Controller Area Network) from Amazon for about $36.00.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Amazon CAN scanner link for about $35.00:

https://amzn.to/3R9lJ60

Please let us know what you find.
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Friday, September 23rd, 2022 AT 12:14 PM
Tiny
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Image of the fuse box cover is added. Module HEV is not shown.
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Friday, September 23rd, 2022 AT 9:05 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,940 POSTS
They would be the module fuse 7.5 amp. I see two of them in the diagram. With the system on do these fuses have power?
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Saturday, September 24th, 2022 AT 10:24 AM

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