12 volt battery location and charging

[mindmachine]

I tried searching but couldn't find the posts on this topic
I am buying an i3 Rex that has been at the dealer for months
I always like to top off the 12 volt battery on any newly purchased car
Where is it, and is ther any thing special about charging it .
I have a deltran 3 amp trickle charger

Thnks in advance

Charging the 12 volt battery directly is not recommended as it is charged when you charge the HV battery using EVSE. Even if the 12 volt battery drops to low to activate the computers, BMW says to plug in the EVSE to charge the 12 volt and not to try charging it directly. The 12 volt is also charged when the vehicle is in ready mode and while being driven via the HV battery.

 

[jadnashuanh]

The owner's manual says you can damage the car if you try to charge the 12vdc battery! IOW, DON'T! Now, I suppose if you disconnected it, you could, but not sure what effect that would have on things like many of your presets which may be held because of the 12vdc battery.

 

[GodFollower]

It is under the passenger side frunk velcro panel, but way back towards the firewall. Not easily accessible. And as others have said, not a good idea to put a charger on it. You can toast the capacitors in the EME if it kicks on the DC/DC converters while you are charging it, if your voltage is higher than it is.

 

[Junior Tibby]

Question: when you remotely activate climate control does this charge the 12v battery?

 

[EvanstonI3]

Question: when you remotely activate climate control does this charge the 12v battery?

Yes but it is not necessary as I have documented that if the 12v battery discharges to exactly 12.0 volts, the car comes on automatically and "boosts" the 12v battery for exactly One Hour.

If the 12v is in good health, this will continue as long as needed.
If, however, the 12v battery is failing and self-discharging rapidly, the car will not be able to keep up and at some point the 12v battery will just die.

 

[Junior Tibby]

Yes but it is not necessary as I have documented that if the 12v battery discharges to exactly 12.0 volts, the car comes on automatically and "boosts" the 12v battery for exactly One Hour.

If the 12v is in good health, this will continue as long as needed.
If, however, the 12v battery is failing and self-discharging rapidly, the car will not be able to keep up and at some point the 12v battery will just die.

Excellent. I’m installing a thinkware u3000 and they encourage you to purchase their backup battery to avoid draining the 12v (battery) but going by what you say this would be redundant.

 

[EvanstonI3]

Excellent. I’m installing a thinkware u3000 and they encourage you to purchase their backup battery to avoid draining the 12v (battery) but going by what you say this would be redundant.

perhaps. but don't plug it into the power plugs as they all shut off after about 15 minutes when the car is turned off. Depending on the draw, you may encounter "Battery Discharged While Stopped" error messages, which would refer to the HV battery draining (to charge the 12v) while the car is not "on".

 

[Junior Tibby]

It’s connected via the OBD2. It also discovered it has a feature within the settings to switch itself off if it has drained the battery too much.

 

[alohart]

Yes but it is not necessary as I have documented that if the 12v battery discharges to exactly 12.0 volts, the car comes on automatically and "boosts" the 12v battery for exactly One Hour.

If the 12v is in good health, this will continue as long as needed.
If, however, the 12v battery is failing and self-discharging rapidly, the car will not be able to keep up and at some point the 12v battery will just die.

I wish that I could find documentation for this automatic 12V charging feature. Even though my 12V system logger has recorded this happening at voltages as high as 12.5V, I don't trust it to maintain the 12V battery while we're away for 3 or more months. In these cases, I just disconnect the 12V battery's negative cable to make sure that it isn't discharged while we're away.

 

[alohart]

Depending on the draw, you may encounter "Battery Discharged While Stopped" error messages, which would refer to the HV battery draining (to charge the 12v) while the car is not "on".

The i3's battery warning messages aren't always clear as to whether the battery referenced is the HV battery pack, the 12V battery, or the fob battery. I have always interpreted "Battery Discharged While Stopped" as referring to the 12V battery because the HV battery pack doesn't discharge noticeably while an i3 is off. I have seen this message even when automatic 12V battery charging had not occurred, so the HV battery pack's charge level hadn't decreased noticeably while that of the 12V battery had.

 

[robthebold]

The i3's battery warning messages aren't always clear as to whether the battery referenced is the HV battery pack, the 12V battery, or the fob battery. I have always interpreted "Battery Discharged While Stopped" as referring to the 12V battery because the HV battery pack doesn't discharge noticeably while an i3 is off. I have seen this message even when automatic 12V battery charging had not occurred, so the HV battery pack's charge level hadn't decreased noticeably while that of the 12V battery had.

It's sometimes impossible to determine what a German means by their words alone. Even a simple checkbox in a configuration only means "check this box once, and once only mein leibschen, after vich vee schall szee" and not like checked and done that the rest of the world might assume when finishing their shopping list.