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I have a 2017 330e (25 kmiles) which I am happy with, except it needed its starter motor replaced twice and now its 12 V battery in the trunk has failed says my dealer (under warranty).

What I don't understand is the electric power architecture of this vehicle. When driving with the electric motor and the gas engine kicks in -- does it really use the 'old fashioned' starter motor, or does the transmission (and HV electric motor in it) spin:dunno: the engine to start ?

Last week, I got a 'drivetrain error' (and it said I could continue to drive) -- it felt like I had limited electric motor power, but the gas engine was fine (including starting and stopping as demand changed) -- but the dealer's diagnostics told him to replace the starter ! Car was fine for a few days, but then today, it won't do electric mode (gas only), and dealer now says the 12 V battery in the trunk is bad (and there are no user warnings or errors). Does this sound reasonable ? The car started and drove OK on gas; it wouldn't drive on electric (although battery was at 100 %), and when slowing down, the dash showed regeneration was happening --> the motor/HVBattery system was at least partially working._a__a2_
 

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Dave
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Your starter motor is powered by the 12 volt battery in the trunk. That's probably why the car will not Start/stop or go into EV mode.

Your 12 volt battery shouldn't have failed already. What happened? Did it sit over the winter without a battery tender hooked up?

Starter failure is not uncommon for any 3 series using start/stop. A Tech told me the motor was revised and strengthened. Probably right after yours was made !!
 

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Discussion Starter #3
Thanks for the reply -- but the car DOES start (in gasoline mode) -- with no problems. Last week (with the drivetrain error needn't a starter replacement), it still switched seamlessly between gas & electric modes. I didn't get a sense the 12 V battery was becoming weak.

I live in the SW US, and generally 12 V batteries fail in the middle of summer here, not in the pleasant winter temperatures.
 

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I live in the SW also and I have had my 2018 530e for thirteen months and no problems. It is easy with BMWs to have battery draining features running without one knowing it. Recently I shut down my car in my garage and went inside. Everything off (turned off car with button after taking foot off brake and accelerator; then opened door). Came back and opened passenger door to toss a note onto the passenger seat for later shopping use. The interior lights came on (as they should) but the dash lit up as well and didn't turn off until I got my car keys and went through the turn off routine again.

I haven't had to use it but I did pick up a BMW trickle charger for any time I would leave the car for more than a few days without driving.

But you shouldn't be having these kinds of problems.
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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17,461 Posts
Wow. Gotta URL Not Found error at www.NewTIS.info for 330e. I wanted to see its electrical architecture too, and that is precisely the proper description of the interest, ***8216;architecture***8217;.
 

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Discussion Starter #6
What I don't understand is:
a) why is the 12 V battery needed for EV mode ? (Even if it is needed for gas mode, and that works OK)
b) if the 12 V fails or is discharged why isn't there a fault indicated ?
 

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Dave
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What I don't understand is:
a) why is the 12 V battery needed for EV mode ? (Even if it is needed for gas mode, and that works OK)
b) if the 12 V fails or is discharged why isn't there a fault indicated ?
The radio, lights, lights on the dash, your electric heat, electric A/C and just about everything runs on 12 volts. I really doubt any of the componentes run on the 293 volts the traction battery supplies. They wouldn't run that heavy of wiring.

Think of your battery of almost an accumulator, or maybe a capacitor in the system.

That why I always wanted more instrumentation in cars. With as technical iDrive is, they could have added a page with battery voltage, water temperature, oil pressure and so on.
 

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Dave
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Wow. Gotta URL Not Found error at www.NewTIS.info for 330e. I wanted to see its electrical architecture too, and that is precisely the proper description of the interest, 'architecture'.
Ah, a technical junky, huh?

Here's a little on the starter:
https://www.newtis.info/tisv2/a/en/f30-330e-iperformance-lim_201711/wiring-functional-info/power-train/hybrid-car/starter-unit/1VnXlsN5DT

If you like this kinda stuff like I do, there's some juicy reads here. If you want, I can PM you the last 7 of my VIN, then you can satisfy your "urge".
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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17,461 Posts
Ah, a technical junky, huh?

Here's a little on the starter:
https://www.newtis.info/tisv2/a/en/f30-330e-iperformance-lim_201711/wiring-functional-info/power-train/hybrid-car/starter-unit/1VnXlsN5DT

If you like this kinda stuff like I do, there's some juicy reads here. If you want, I can PM you the last 7 of my VIN, then you can satisfy your "urge".
Thanks for the read. I hope that BMW provided a customer acknowledged caution against mechanics less than well qualified working on this car. Two IBS, two batteries, a high-tech starter will kick some shadetree ass.
 

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Dave
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134 Posts
"It's not the volts, but the amps that gets you." Isn't that what all the dead people used to say?

Oh well, after all, it's only DC.
 
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