[javapro]

I am just curious how does 45e keep the 12 volt battery charged if one always drives in electric mode? Does 45e use the hybrid battery to start the ICE? My Lexus hybrid (non-plug-in) only used the 12 volt battery to start the ICE so the car wouldn’t start if the 12 volt battery was discharged even though the hybrid battery was near full capacity.

[SmartSaves]

12v battery is separately charged by the starter generator and it shouldn't be depleted much, otherwise the 45e won't start. High voltage battery is not used for vehicle starting/cranking function (only BMW knows why). May be that tech is for EV only.

[AlZ4]

From what I’ve read, the high voltage system powers the electric motor, charges the 12v system, heats and cools the heat exchangers for interior and battery heating and cooling when the 45e is in operation and the ICE is not running. The 12v system power the entire vehicle including all electronics that control the electric motor, interior and exterior lighting, seat/steering heat/ventilation, ICE startup and more. So the vehicle will not move even if the high voltage system is 100% full and the 12v system is dead.

[nZtiZia]

so which one charges the 12V battery?
1) starter generator
2) high voltage system

source of info, please and thanks!

[biterror]

Originally Posted by nZtiZia

so which one charges the 12V battery?
1) starter generator
2) high voltage system

source of info, please and thanks!

The 12 V battery is charged by a DC/DC converter which is powered by the HV battery.

[AlZ4]

If you think about it, the ICE is not spinning in electric only mode so the starter/generator which is attached to the ICE is not spinning and therefore can’t be charging anything.

[nZtiZia]

ok, so when the 45e is in electric mode (99% of the time for me), the HV system keeps the 12V battery charged via the DC/DC converter. when the 45e's ICE is running, the starter/generator spins and therefore keeps the 12V battery charged.

[AlZ4]

Originally Posted by nZtiZia

ok, so when the 45e is in electric mode (99% of the time for me), the HV system keeps the 12V battery charged via the DC/DC converter. when the 45e's ICE is running, the starter/generator spins and therefore keeps the 12V battery charged.

Yes. That is my understanding of how it works. The mild hybrid system on other models works differently, I.e. the ICE is always spinning, which I think causes some confusion.

[javapro]

Originally Posted by nZtiZia

ok, so when the 45e is in electric mode (99% of the time for me), the HV system keeps the 12V battery charged via the DC/DC converter. when the 45e's ICE is running, the starter/generator spins and therefore keeps the 12V battery charged.

Gotta be this way otherwise the 12V will keep getting depleted if one drives in electric only mode all the time.

[javapro]

Originally Posted by AlZ4

Yes. That is my understanding of how it works. The mild hybrid system on other models works differently, I.e. the ICE is always spinning, which I think causes some confusion.

Yes, non-plug-in hybrids like the Lexus RX 450h I had before charges the 12V battery off the ICE similar to normal gas cars.

[nZtiZia]

Understood. Taking it a step further, the 45e uses the 12V battery to start the ICE, not the high voltage battery, and because of its two systems that keep the 12V battery charged, the 45e won't run into that starting issue your Lexus hybrid had.

so how did you work around this issue with your Lexus? forced periodic ICE usage or battery tender?

javapro

[AlZ4]

Originally Posted by nZtiZia

Understood. Taking it a step further, the 45e uses the 12V battery to start the ICE, not the high voltage battery, and because of its two systems that keep the 12V battery charged, the 45e won't run into that starting issue your Lexus hybrid had.


javapro

You can still run into this issue if the 45e is parked for a long period (weeks) of time, even if the high voltage system is being charged. The high voltage system only charges the 12v system while in ready-drive mode not while parked. Also if your 12v battery goes bad due to age or etc, you can run into this same problem.

[biterror]

Originally Posted by nZtiZia

Understood. Taking it a step further, the 45e uses the 12V battery to start the ICE, not the high voltage battery, and because of its two systems that keep the 12V battery charged, the 45e won't run into that starting issue your Lexus hybrid had.

I _think_ the ICE is started by the electric engine which runs off the HV battery (no 12 starter motor). However, the 12 V systems control everything in the vehicle, so without 12 volts, nothing works.

And I believe the 12 V battery/batteries are not charged by the DC/DC converter when the car is sleeping. The DC/DC converter is running when the car is running - and probably when the HV battery is being AC charged.

I really wish BMW gave us more information.

[nZtiZia]

Originally Posted by AlZ4

You can still run into this issue if the 45e is parked for a long period (weeks) of time, even if the high voltage system is being charged. The high voltage system only charges the 12v system while in ready-drive mode not while parked. Also if your 12v battery goes bad due to age or etc, you can run into this same problem.

a scenario like this?
my 45e sits for many weeks, depleting its 12V battery. high voltage battery is fully charged, though. my car is coded to start in Sport Individual, but because the 12V battery is depleted, it won't start the ICE or go into drive-ready mode. at this point, can i select ELECTRIC, HYBRID OR ADAPTIVE modes to get into electric drive-ready mode and drive away? then as i'm driving, the high-voltage systems begins to charge the 12V battery? or will i not even be able to get into electric drive-ready mode because i coded my car to start in Sport Individual?

Originally Posted by biterror

I _think_ the ICE is started by the electric engine which runs off the HV battery (no 12 starter motor). However, the 12 V systems control everything in the vehicle, so without 12 volts, nothing works.

And I believe the 12 V battery/batteries are not charged by the DC/DC converter when the car is sleeping. The DC/DC converter is running when the car is running - and probably when the HV battery is being AC charged.

I really wish BMW gave us more information.

yeah, something more informative would be nice. i don't think BMW really understands there are enthusiasts who want to understand its vehicles' technicalities deeply.

Auricom anything in your notes?

[AlZ4]

Originally Posted by nZtiZia

a scenario like this?
my 45e sits for many weeks, depleting its 12V battery. high voltage battery is fully charged, though. my car is coded to start in Sport Individual, but because the 12V battery is depleted, it won't start the ICE or go into drive-ready mode. at this point, can i select ELECTRIC, HYBRID OR ADAPTIVE modes to get into electric drive-ready mode and drive away? then as i'm driving, the high-voltage systems begins to charge the 12V battery? or will i not even be able to get into electric drive-ready mode because i coded my car to start in Sport Individual?

Auricom anything in your notes?

If your 12v battery is dead, no you can’t put in it any mode as the electronic are controlled by the 12v battery and the electronics would not start up. There would be no starting it at all without a jump or charging the 12v battery first. Once started either the high voltage or ICE would charge it if the dead 12v battery would accept the charge.

[nZtiZia]

Originally Posted by AlZ4

If your 12v battery is dead, no you can’t put in it any mode as the electronic are controlled by the 12v battery and the electronics would not start up. There would be no starting it at all without a jump or charging the 12v battery first. Once started either the high voltage or ICE would charge it if the dead 12v battery would accept the charge.

yes yes! cuz the 12V battery controls all electrical systems...
moral of story: don't let the 12V battery die...ever

[javapro]

Originally Posted by nZtiZia

Understood. Taking it a step further, the 45e uses the 12V battery to start the ICE, not the high voltage battery, and because of its two systems that keep the 12V battery charged, the 45e won't run into that starting issue your Lexus hybrid had.

so how did you work around this issue with your Lexus? forced periodic ICE usage or battery tender?

javapro

I had to jump my Lexus

[javapro]

Originally Posted by AlZ4

If your 12v battery is dead, no you can’t put in it any mode as the electronic are controlled by the 12v battery and the electronics would not start up. There would be no starting it at all without a jump or charging the 12v battery first. Once started either the high voltage or ICE would charge it if the dead 12v battery would accept the charge.

This is exactly what happened to my RX hybrid - the 12V battery died after the car hasn't been driven for two weeks. So, I had to jump it. The only difference between non-plugin Toyota hybrids and PHEVs is that the 12V battery is charged not only by the ICE but also by the hybrid battery since one can drive on PHEV without ever using the ICE.

[codex57]

Teslas work the same way. There's a separate 12v which does get charged by the main battery similar to how the BMW does it. If the 12v goes dead, the car is dead (until replaced). It's sort of a hot topic on the Facebook groups I'm in because the Tesla 12v sometimes gives very little warning before it dies. You can get anywhere from 2-3 weeks to no warning at all until it's already dead.

[jad03060]

The i3 has a backup 12vdc trickle charger if that battery dies and it is plugged in with an EVSE...it will take a very long time to bring that battery back up, if ever. I do not know if that same logic/hardware exists in the X5 45e.

But, all of the computers, fans, etc., in the vehicle are primarily powered by 12vdc, so it won’t turn on unless there’s enough voltage on that bus to recognize you actually pressed the button.

[Walrusmode]

Just came across this thread and after reading through all the posts, I'm still very confused.

So there is def both a 12v battery and an EV battery, that is clear. 12v battery starts up the car and powers the electrical equipment like radio, navigation, etc.

EV battery powers the electric drive motors only or are there other things it powers too such as A/C?

So does the EV battery charge the 12v battery or not?

Does it only charge while driving (either in Electric mode or a mode that uses ICE too)?

How much and how often do you have to drive in either mode to make sure your 12v maintains sufficient charge to not die?

How long can one leave the car idle before the 12v battery dies?

If the 12v battery dies, can you no longer start the car unless you get a jump?

[dynamic]

Originally Posted by codex57

Teslas work the same way. There's a separate 12v which does get charged by the main battery similar to how the BMW does it. If the 12v goes dead, the car is dead (until replaced). It's sort of a hot topic on the Facebook groups I'm in because the Tesla 12v sometimes gives very little warning before it dies. You can get anywhere from 2-3 weeks to no warning at all until it's already dead.

It is quite interesting and most enlightening to read these threads which relate real life, real world, experiences and the dark side of this EV stuff as they currently exist.
Hopefully the many shortcomings of these vehicles can be rectified soon.