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Discussion Starter #1
Less than 30k miles. OEM battery already replaced by dealer. If I don't keep a float charger on it every week or so, it will just unexpectedly go dead. I know I don't drive as much as many, but recently it went dead after the following: a six hour interstate drive, followed within a week, by a one hour interstate drive, and a one hour freeway drive. Mostly short trips to the grocery store in between. Then it went dead when I went to pick up a curbside restaurant pickup. I have been turning off the auto headlight and AV system when shutting off the ignition. Any ideas? Normal for a low mileage driver? My wife thinks there's a defect, because her 2014 Dodge Caravan always starts.
 

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Less than 30k miles. OEM battery already replaced by dealer. If I don't keep a float charger on it every week or so, it will just unexpectedly go dead. I know I don't drive as much as many, but recently it went dead after the following: a six hour interstate drive, followed within a week, by a one hour interstate drive, and a one hour freeway drive. Mostly short trips to the grocery store in between. Then it went dead when I went to pick up a curbside restaurant pickup. I have been turning off the auto headlight and AV system when shutting off the ignition. Any ideas? Normal for a low mileage driver? My wife thinks there's a defect, because her 2014 Dodge Caravan always starts.
Add any aftermarket gear?

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Sounds like a switch is going bad. If the BCM doesn't see all the doors and other switches in the proper state it will not go to sleep and it'll drain it overnight.
 

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Batteries don't last long if they go dead, you may already need a new one. Have you had the alternator checked...it should read something like 14.5 volts on the battery when running.
 
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Discussion Starter #5
Thanks for the replies. Nothing is aftermarket. This is already the second battery, but at least the OEM tested bad and they replaced it. The dealer has tested the battery and charging system 3 or 4 times now, with the same result every time. They say the alternator and battery are good, it's just that I don't drive enough to keep it charged. After the last 2 weeks with many hours of 70-80 mph highway driving, I found it hard to believe. Could a door switch go bad without showing on the dash? Normally a nice illustration of an open door shows on the dash when one is open...everything seems to be operating normally except for the failure to start if I don't keep the float charger on it pretty regular.
 

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Normally a nice illustration of an open door shows on the dash when one is open...everything seems to be operating normally except for the failure to start if I don't keep the float charger on it pretty regular.
Yes you're right about the door showing open on the dash. They need to check the current drain with everything turned-off...it should be less than 100 mA.
 
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They need to check the current drain with everything turned-off...it should be less than 100 mA.
It should be significantly less than that.
50mA is the maximum drain the Hyundai shop manual says your allowed. But in my experience of testing various different cars I find it is typically less than half of that.

If I helped you fix it, why not...

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Discussion Starter #9
I'm gonna ask the dealer what the parasitic current draw is. Hopefully they included that as part of their electrical system checks. Way back in my ancient history I had a clamp on milliammeter. Long since defunct. Otherwise I would double check the dealer's conclusions. Actually I've been out of automotive servicing as a career, since 1987. So my stock of tools has dwindled, as the technology has increased...
 

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I just purchased a 2019 Elantra with a dead battery. Your thread makes me worry.
The dealer is going to change the battery but I hope there is nothing serious as I intend to add a Thinkware dashcam. The dashcam was previously installed on my old Elantra and in parking mode it was running for weeks with no issues.
Here another Elantra 2019 complaint.

Let us know what was the culprit in your case.
 

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Discussion Starter #12
I just purchased a 2019 Elantra with a dead battery. Your thread makes me worry.
The dealer is going to change the battery but I hope there is nothing serious as I intend to add a Thinkware dashcam. The dashcam was previously installed on my old Elantra and in parking mode it was running for weeks with no issues.
Here another Elantra 2019 complaint.

Let us know what was the culprit in your case.
No culprit yet, dealer wants me to use my float charger since I don't drive much. But it did go dead recently after extended highway driving. I do have some automotive service experience (years ago) and we would often find dead batteries coming in with new cars from the port. Standard procedure was to put the battery on slow charge and watch the specific gravity. If it came up, the battery would be okay. If it didn't, we replaced the battery. Not possible to measure sp gr in these batteries LOL!
 
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