Dead battery - OBD-II power and cigarette lighter power?
 

Hi

2 weeks ago I acquired brand new 2020 BRZ Final Edition as my first very own car :happyanim:

Unfortunately soon after I caught covid and last friday fever kicked in so I was dying in bed for like 5 days and thus I wasn't able to drive my BRZ. However as soon as I was able to somewhat get up from bed on my own and crawl in pain down the stairs to the garage I decided It's high time for a ride.

Unfortunately when I arrived to garage I got greeted by complete brick. Couldn't even get into car I had to use mechanical key. Attempt to start car using jumper cables connected to old Opel Astra H also failed - BRZ didn't even attempt to crank. When I attempted to take battery out in order to charge it at home, my charger threw up error and claimed battery is completely dead.

Multimeter measured around 6.2v which kinda does indeed sound like dead battery. It seemed really sus at first especially since car is brand new, but then I found some thread on this forum where some dude also killed his battery using OBD-II dongle. Indeed, about week ago I installed Vgate iCar Pro dongle (wifi version which afaik draws more power than BT one).

I never had any issues with this dongle in my father's Astra ctdi that I was driving for like 2 years, even after leaving it in OBD-II port for like week, but then again Astra had significantly bigger battery (72 Ah iirc) and most likely significantly less electronics draining battery.

It came as surprise to me that this dongle caused such catastrophic battery drainage in BRZ and really made me question what could go wrong? How OBD-II in BRZ is different from one I had in Astra? Does BRZ keep ECU up when it detects that something is up and running in OBD-II port? Does it have some kind of voltage stabilization that fools OBD dongle into thinking that car is running and prevents it from entering sleep mode? Does anyone know how OBD-II port in BRZ is powered and why car was able to drain battery so quickly despite being turned off?

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Another question related to this issue is cigarette lighter power. I have low power sensor with LTE modem that sends me notification when it detects that cigarette voltage drops below 12.2V. In Astra it did in fact work great since cigarette lighter was always powered. Unfortunately that's not the case with BRZ.

So is it possible to change this behavior and make BRZ keep cigarette power on when ignition is off?

I'm complete noob and this is my gateway car that is supposed to teach me more about how cars operate so sorry if my questions are super silly.

before nuking everything from orbit, do you even know for sure that the battery was good? it's entirely possible that the battery went bad all by itself.

if the new battery goes dead after 5 days with the OBD thingie plugged in, the first diagnostic step is to unplug it, recharge the battery, and see if that's enough to hold over for 5 days--if it is, then it's an issue with the obd thingie. if it still goes dead, the issue is somewhere else.

there is no easy way to make the cigarette lighter powered constant. there's plenty of wiring methods to make it work, but there's no programming or jumpers that simply change the state. it is inherent to the way toyota builds vehicles.

I just verified that obd dongle drains at most 50 mA which at 12V over 4 days is like... 50 Wh. Sounds like some completely irrelevant amount of power in context of draining entire car battery. If anything, it could be related to some in-car electronics remaining running due to presence of obd dongle but for sure not dongle by itself :/

Oh... What is "Toyota way" of installing parking dashcams in such case? Hook up directly to fuse?

I doubt I'll have occasion to leave this car in garage for 4 days any soon haha :D For now Subaru took battery and claimed they'll recharge it and diagnose if it's working properly. So I'm waiting till Monday for verdict. Just wanted to seek for source of issue before I'll have to run again to Subaru service with dead battery.

i believe most parking dash cams have their own internal battery that recharges whenever the car is running.

If I'd like to check eg. after 1 day whether OBD dongle actually affects discharge rate of battery, can I use multimeter on live battery? As in without unplugging it from car, just stick multimeter to terminals when car is turned off?

yes, you can use a multimeter while the battery is still connected.

6.2v doesn't sound unrecoverable... do you have a trickle charger?

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Yeah I do but unfortunately one I have refuses to charge this battery. It enters "error mode" and claims battery is damaged. That's why I took it to service. Maybe they'll be able to charge it. I heard many trickle chargers refuse to charge batteries below 10v so that may be why mine didn't even try to bring it back to life. It's apparently because below 10v you can't be sure whether it's deep drainage or shorted cell and charging battery with shorted cell could be potentially dangerous by leading to hydrogen emission and possibly leakage thus "consumer" chargers don't allow that.

Turns out battery was drained by ISR system which couldn't connect through concrete garage walls and drained above average power. ISR (autonomous emergency notification device) is mandatory in EU for all new vehicles so my BRZ has it added as external module which probably isn't integrated really well with car circuitry and doesn't care about draining battery.

ISR is small device like this, attached to ceiling:

https://ocdn.eu/pulscms-transforms/1...LNAeAAwsOBoTAF

Case closed.

I knew it was a government conspiracy!

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My tactrix drains my battery flat overnight and I know of multiple users who experience the same thing.
Before throwing out the battery, find a dummy 12v source to charge it with.
Battery chargers have all sorts of current limiting and pwm circuitry inside them as well as undercharge protection which can often render them useless for very flat batteries.
If you can source a 12v dummy power source, like an old computer power supply or a decently sized DC power pack like those used by routers, hook it up and give it a few hours. It should bring the battery up to a voltage that the charger will work from. Otherwise leave your other car connected to it with jumpers for 20 minutes or so.
Don't leave a small DC power pack on overnight however, as it will get quite hot with that amount of current draw. It should be fine but I wouldn't leave it unattended for more than an hour at a time.

-electrical engineer (not that it makes a difference).