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Discussion Starter · #1 ·
I have a 2015 Infiniti Q50s with just over 40K miles. I've had it for almost 6 years and it's been well taken care of. Almost a year ago (Dec 2021), I experienced a total loss of power with no previous indication of any issues (no check engine lights, or degrading power like you see when your alternator fails). I replaced the battery and was good to go for 2 months. Then it died again. Had it towed to my dealership where they couldn't find anything except that the new battery had been completely drained. The dealership charged the battery, but I went back to Advanced Auto and had them replace it even though it was registering good. Fast forward 4 months and the car died again. Took it back to the dealership and after several days they couldn't find anything wrong except the replacement battery (2nd new battery) was registering failure. So once again, I paid over $250 to Infiniti and still did not have an answer as to what the real problem is. I replaced the battery for the 3rd time and everything was good from June until now (Nov 2022) and the car has died again. One day it worked and the next, total loss of power. I can jump start it, but I know it's not a battery issue and the main things were ruled out previously like the alternator and fuel injectors. I'm beyond frustrated because there is definitely something wrong and it appears to be more electrical than anything and the dealership couldn't diagnose it. The other caveat is I had an extended warranty on the car that expired a month ago (Oct 2022) and I can't help but wonder if the dealership didn't diagnose or fix the real problem since it was still under warranty and they wouldn't make any money off the repairs.

Has anyone experienced what I'm dealing with?? I'm wondering if this is a fuse issue or a power cable issue to the starter motor and/or it's connections to the battery. Please share any thoughts or feedback if you've experienced similar issues.
 

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To me, that is a parasitic drain.
How often do you drive the car and for how long?

You can pick up a cheap cigarette lighter volt meter and watch the battery voltage to see what is going on:

Typical good voltages are around 13+ volts.
Any voltage below about 12.5 means the battery is not being charged.
 

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We would need to know your driving habits, are you letting the car sit for a 1-2 weeks between driving it or is it your daily driver? How far is your daily commute in the car?

Modern cars can't sit for extended periods of time before the internal electronics and sensors deplete the batteries. Assuming you drive it almost every day what you described it sounds like the alternator isn't supplying enough power to keep the battery fully topped off or there is an issue with the accessory belt (It could be slipping).

If it was the fuel injectors it wouldn't go away when your car is jump started, it would be an consistent issue.

A shop will start with the most obvious/common issue a drained battery, then on the second visit started at the battery again but saw it had failed and they likely didn't bother checking the alternator because the issue was resolved with a replacement battery. Almost guaranteed they didn't load test the alternator.
 

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Discussion Starter · #4 ·
To me, that is a parasitic drain.
How often do you drive the car and for how long?

You can pick up a cheap cigarette lighter volt meter and watch the battery voltage to see what is going on:

Typical good voltages are around 13+ volts.
Any voltage below about 12.5 means the battery is not being charged.
Thank you for your reply and the Amazon link. I drive the car less than 15 miles per day M-F and it typically sits on the weekend.
 

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Discussion Starter · #5 ·
We would need to know your driving habits, are you letting the car sit for a 1-2 weeks between driving it or is it your daily driver? How far is your daily commute in the car?

Modern cars can't sit for extended periods of time before the internal electronics and sensors deplete the batteries. Assuming you drive it almost every day what you described it sounds like the alternator isn't supplying enough power to keep the battery fully topped off or there is an issue with the accessory belt (It could be slipping).

If it was the fuel injectors it wouldn't go away when your car is jump started, it would be an consistent issue.

A shop will start with the most obvious/common issue a drained battery, then on the second visit started at the battery again but saw it had failed and they likely didn't bother checking the alternator because the issue was resolved with a replacement battery. Almost guaranteed they didn't load test the alternator.
Thank you for your reply. I drive the car less than 15 miles per day M-F and it typically sits on the weekend.
 

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Thank you for your reply. I drive the car less than 15 miles per day M-F and it typically sits on the weekend.
While on the low end for a daily commute should be enough to keep the battery topped off, probably the alternator or belt then.
 

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I'm wondering if there is a bad ground connection related to the charging system. The car and battery is found dead and then people are focusing on replacing the battery. It's possible that there is an issue with the actual charging system which isn't maintaining the battery properly. If the issue is intermittent, there could be a weak or bad ground connection associated that is not allowing for proper charging when the car is running.

Also, just a note on warranty repairs. There isn't much incentive for the dealership to deny warranty, because they are paid by the warranty company (Infiniti or 3rd party depending on the warranty provider) to complete the repairs. In other words, the dealership isn't completing the work for free.
 
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This is a known issue since the Infiniti G37 where the charging system has a Variable Voltage Control System from Infiniti. This is supposed to be there smart system for charging the vehicle where the alternator only see fit to provide full voltage when needed otherwise it will not and cause a drain on the battery while driving and after you have driven it will just sit there with a very low voltage. This is caused due to very minimal driving by the owner of the vehicle and a poorly designed charging system voltage control feature which doesn’t allow the car to charge like normal cars which provides full voltage all the time. Some recommendation is drive the car as every so often so that the battery is able to get a consistent charge and the Variable Voltage Control System is able to provide that full charge when driving.
 

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This is a known issue since the Infiniti G37 where the charging system has a Variable Voltage Control System from Infiniti. This is supposed to be there smart system for charging the vehicle where the alternator only see fit to provide full voltage when needed otherwise it will not and cause a drain on the battery while driving and after you have driven it will just sit there with a very low voltage. This is caused due to very minimal driving by the owner of the vehicle and a poorly designed charging system voltage control feature which doesn’t allow the car to charge like normal cars which provides full voltage all the time. Some recommendation is drive the car as every so often so that the battery is able to get a consistent charge and the Variable Voltage Control System is able to provide that full charge when driving.
I'm pretty sure all modern cars use a variable charging system.
 

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I'm pretty sure all modern cars use a variable charging system.
That's my understanding. Ford and GM definitely do.
This is a known issue since the Infiniti G37 where the charging system has a Variable Voltage Control System from Infiniti. This is supposed to be there smart system for charging the vehicle where the alternator only see fit to provide full voltage when needed otherwise it will not and cause a drain on the battery while driving and after you have driven it will just sit there with a very low voltage. This is caused due to very minimal driving by the owner of the vehicle and a poorly designed charging system voltage control feature which doesn’t allow the car to charge like normal cars which provides full voltage all the time. Some recommendation is drive the car as every so often so that the battery is able to get a consistent charge and the Variable Voltage Control System is able to provide that full charge when driving.
I don't think your explanation is accurate. The battery current sensor detects the charging/discharging current of the battery and sends the corresponding voltage signal to the ECM. The ECM determines whether to perform variable voltage control according to battery condition and sends the target voltage to the IPDM, which in turn converts that target voltage into a PWM signal to the IC voltage regulator in the alternator. The alternator will output 11.4 - 15.6 VDC when operating in variable voltage control. Otherwise, the alternator provides between 14.1 - 14.7 VDC when there is no PWM power generation command signal coming from the ECM.
 

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"Total loss of power" doesn't exactly paint the whole picture for us.
Do you mean; 1) As you're driving, the engine and everything electrical shut down and off and you come coasting to a stop? Or 2) There isn't enough juice in the battery to even start the car? Or D) None of the above.

Regardless if it's 1 or 2, it does indeed sound like a loose ground wire/connection somewhere, probably connected to the battery/starter system. That's absolutely where I would start looking, having had extremely similar problems on multiple cars.
 
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