Interesting USB bug that left my battery dead. - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

F14Scott · 01-14-2019, 03:15 PM

I wanted to charge an external Lion battery pack while I drove, so I plugged it into my '18 BRZ USB port, where it began charging immediately. When I shut down the car, however, it then reversed its flow and started trying to charge my car. This introduced current confused the car, which then did not shut down my radio or Bluetooth when I opened my door.

The next morning, the car's battery was dead. I charged it and all was well. When I don't have the Lion battery plugged in, the car shuts down and acts normally.

So, the moral of the story is that current applied to the USB port at engine shutdown might inadvertently command some accessories to remain powered up, draining the car's battery, eventually.

Cheers!

Sent from my SM-G965U using Tapatalk

LimitedSlip · 01-14-2019, 03:28 PM

Unless there is a good reason to allow DC current flow back into the vehicle from the USB port it would seem reasonable that a diode might be a good addition to the circuit. It may not be that simple, however, depending upon how DC and data are combined in the physical circuitry.

01-14-2019, 03:15 PM	#1
F14Scott Member Join Date: Sep 2018 Drives: Posts: 15 Thanks: 10 Thanked 8 Times in 7 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Interesting USB bug that left my battery dead. I wanted to charge an external Lion battery pack while I drove, so I plugged it into my '18 BRZ USB port, where it began charging immediately. When I shut down the car, however, it then reversed its flow and started trying to charge my car. This introduced current confused the car, which then did not shut down my radio or Bluetooth when I opened my door. The next morning, the car's battery was dead. I charged it and all was well. When I don't have the Lion battery plugged in, the car shuts down and acts normally. So, the moral of the story is that current applied to the USB port at engine shutdown might inadvertently command some accessories to remain powered up, draining the car's battery, eventually. Cheers! Sent from my SM-G965U using Tapatalk

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01-14-2019, 03:28 PM	#2
LimitedSlip Senior Citizen Member Join Date: Jul 2018 Drives: Then-1977 Celica GT Now-2017 860SE Location: In A Galaxy Far Far Away Posts: 393 Thanks: 145 Thanked 385 Times in 201 Posts Mentioned: 12 Post(s) Tagged: 1 Thread(s)	Unless there is a good reason to allow DC current flow back into the vehicle from the USB port it would seem reasonable that a diode might be a good addition to the circuit. It may not be that simple, however, depending upon how DC and data are combined in the physical circuitry.

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