Well I got the dreaded, 12v battery fail this morning in my 2024 Prime. Had it towed to the Toyota dealership. The battery was replaced, but the mechanic that worked on my car made a note on my paperwork saying, don't use aftermarket plugins in the front USB ports, that is what drained my battery. I don't understand because when I turn off the car, anything that's plugged into those ports shut off with the car. Mechanic claims they are still pulling power from those USB ports. Your thoughts please.
I wouldn't worry about it. Your correct, those accessory ports are on a relay and turn off with the car. If you encounter this again, tell the idiots to look-up the TSB's related to this issue, before making snap judgements.......
LoL, we do the same at our facility - assign the idiots to a job where they'll do the least amount of damage when they screw-up. It's not a matter of if, but when......
If you have a multimeter, and would like to see for yourself what's happening: put in series between the negative battery post and ground, close up the car, fob well away, wait half an hour, see what sort of milliamperes, or amperes, it's drawing. Should be around 20~30 milliamperes.
They shouldn't be a problem. Get a Bluetooth BM2 battery monitor from Amazon or at least a cigarette-lighter voltmeter. The BMS on Gen 4/Gen 5 is very miserly and hardly ever charges the 12-V battery. Therefore, get a battery maintainer like a Noco Genius to occasionally bring the SOC to 100%, as the BMS never does so and the SOC can keep going lower and lower with ever-increasing sulfation especially if the car is not driven for at least one hour a few times a week.
If your USB sockets are live when your car is turned off, I'd like to know how you do it. My USB sockets are off whenever I stop my car, and it's a bit of a pain sometimes, when I wish they'd stay on.
I think I'd be looking for a different mechanic. If he hasn't bothered to actually measure parasitic drain through your USB sockets, it sounds like he's just guessing.
i suppose if you plug something in using max usb power when the car is ready, it might leave the 12v a little lower than if you didn't, if the inverter can't keep up, idk.
I believe the USB ports are limited to 15 watts. The inverter is rated for 100 watts, I think, so it's unlikely that USB power will draw down the system.
