How to prevent a low 12V battery alarm when away for a long period

[scrambler]

Hi,
We are away 2 or 3 months at a time, and I am worried that one day the 12V battery could die or discharge to the point where the alarm would go on and drive the neighbors nuts.
So I have the following questions.

1. If the low 12V battery alarm goes on, how long will its stay on?
2. Is there a way to deactivate the low 12V battery alarm, may be with something like bimmercode?
3. If there is no way to deactivate that alarm, would the best way to proceed, be to disconnect the 12V battery and its High voltage connector while we are away?
4. If so would the prolonged 12V battery disconnection cause any issues with the car?

Thank you for any insights

 

[EvanstonI3]

If the alarm goes off, it means your 12v battery is failed. It is just one of many symptoms when the 12v fails.

If you do not want to simply replace the battery now BEFORE it fails so you can have at least 3 years of driving/use of the car without worrying about the 12v battery, then you should disconnect the negative terminal of the battery before you let it sit.

If the battery is in good condition, it can sit for months while disconnected without losing more than 1-2 volts, which means you can hook it back up when you return and everything will be fine.
If the battery is NOT in good condition, or fails while sitting disconnected, the car will not function when you return but replacing the 12v battery will bring everything back to normal with minimal fuss.

If the car sits for an extended period of time while connected to a failing/failed 12v battery it will cause all sorts of issues and error codes with the car because the car does try to keep it charged and "alive" but at some point it will not be able to keep up and the car gets bricked.

 

[alohart]

There is no 12 V battery alarm. As @EvanstonI3 wrote, the burglar alarm can be triggered when a 12 V battery is failing. However, this would occur only if the 12 V battery's voltage decreases significantly. This feature prevents a burglar from disabling the burglar alarm by disconnecting the 12 V battery because the alarm includes its own internal battery which powers the alarm. The 12 V batteries on our i3's have failed twice without triggering the burglar alarm.

I have stored our i3's 8 times for periods of 3 to 9 months each time. I have always disconnected the HV disconnect followed by disconnecting the 12 V battery's negative cable as @EvanstonI3 suggested. I have always been able to start our i3's after ending their storage by merely reconnecting the 12 V battery's negative cable followed by connecting the HV disconnect. To be safe, I have always charged the 12V battery with a battery charger after disconnecting it and again before reconnecting it. This reduces the possibility of a weak 12 V battery being reconnected at such a low voltage that spurious and occasionally troublesome diagnostic trouble codes (DTC's) might be stored. This isn't necessary for 3 months of storage assuming that you've been driving your i3 regularly prior to storage so that the charge level of its 12 V battery is high.

Some tips:

• Don't disconnect the 12 V battery with the burglar alarm armed (i.e., the doors locked) to avoid triggering the alarm;
• Close but don't latch the hood so that it can be opened when you return without using the emergency unlatch cable;
• With the 12 V battery disconnected, the front windows won't drop when the doors are opened, so be careful opening and closing the doors to prevent damage;
• Lock the passenger door from the inside and use the physical key in the fob to lock the driver door;
• Be sure to reinstall the driver door lock cover securely so that it doesn't fall off while driving.