[Ninja_H]

This topic just came to my attention and I'm interested to know the answer for.

Been doing so when I'm away for few weeks but someone said it will not charge the battery and sometimes drain it.

Curious for the answer and please someone explain the mechanics behind this.

[TurtleBoy]

Depending how long you are away it won't do a remote start as it starts to shut things down to save the battery. Whether or not it will charge the battery when you start it depends on the state of charge of the battery. The vehicle uses brake energy regeneration so the alternator is on a clutch and only charges when coasting or braking. The exception to that is if the battery is below a certain percentage, 60% is most often stated then it will charge until it reaches a specific percentage, 80% it seems. I would assume even idling in park it will engage if it is below the threshold.

[AvGeek]

Best to just leave it on a trickle charger imo, e.g. CTEK 7002.

[BlkGS]

It depends.

If you're talking about just the 12v starting battery in a normal vehicle, yes, it will charge the battery. But, because the vehicle is idling, it won't do so very quickly. You'd likely need to idle it for 15 minutes to pick up any appreciable charge. The alternator spins as a speed based off engine rpm, the faster it spins, the more power it makes, typically they don't make their rated power until 2500rpm or so (it can vary wildly based off many factors)

If you're talking about the mild hybrid or PHEV battery, then no, it won't.

[tooloud10]

Originally Posted by BlkGS

If you're talking about just the 12v starting battery in a normal vehicle, yes, it will charge the battery. But, because the vehicle is idling, it won't do so very quickly. You'd likely need to idle it for 15 minutes to pick up any appreciable charge. The alternator spins as a speed based off engine rpm, the faster it spins, the more power it makes, typically they don't make their rated power until 2500rpm or so (it can vary wildly based off many factors)

Like TB said, it will likely only charge at idle if the charge level is too low, otherwise it will only charge while coasting and braking.

The Fxx cars (at least my old F25) used to have a gauge under the tach that would tell you if/when the battery was charging but they seem to have removed it over the years.

[TurtleBoy]

Originally Posted by tooloud10

Like TB said, it will likely only charge at idle if the charge level is too low, otherwise it will only charge while coasting and braking.

The Fxx cars (at least my old F25) used to have a gauge under the tach that would tell you if/when the battery was charging but they seem to have removed it over the years.

Not sure about 8.5 but iD7 has a BC panel that shows when it is being charged. It is the one displaying the trip data MPG and it has a meter that fills with blue when charging.

[davchr]

If your starting battery NEEDS to be charged when you are gone for a few weeks you NEED a new battery. A few months, put a trickle charger on it.

[TurtleBoy]

Originally Posted by davchr

If your starting battery NEEDS to be charged when you are gone for a few weeks you NEED a new battery. A few months, put a trickle charger on it.

I would agree. I don't use a charger on the M340i when we are gone for a month and have not had any problems.

[tkim91321]

Originally Posted by TurtleBoy

Not sure about 8.5 but iD7 has a BC panel that shows when it is being charged. It is the one displaying the trip data MPG and it has a meter that fills with blue when charging.

TurtleBoy

On iD8/8.5, comfort and eco modes have the battery charge indicator on the gauge below the power/rpm meter. You can also go to the Live Vehicle app to see charge status.

[TurtleBoy]

Originally Posted by tkim91321

TurtleBoy

On iD8/8.5, comfort and eco modes have the battery charge indicator on the gauge below the power/rpm meter. You can also go to the Live Vehicle app to see charge status.

Excellent, thank you for the info.