can I charge the 12v battery through the 12 v socket?

[jashines]

My 12 V battery is apparently dead and has locked the charge door, and the frunk, so I can't get to the battery itself. If I use a car battery charger with the 12v socket attachment, will that charge the battery enough for me to be able to start the car and get it to the dealer?

 

[CanisLupus]

I think the answer is No . The 12V sockets time out and turn off when the car is turned off , so they must be controlled somehow . Hence they are not connected directly to the 12V battery . Below the 'Frunk' , 'Trunk' (and 'Gas Filler' if you have a Rex) buttons there is a small pop open cover that reveals a wire to open the 'Frunk' . I don't think you should just charge the battery while it's connected to the car though . The HV connection should at least be disconnected before doing anything . Search for 'Changing the 12V battery' . There are many topics with instruction as well as videos online .

 

[Anonymous]

If the 12v isn't totally dead or unable to take a charge, it should charge up from the HV traction battery, if the car itself is plugged in to charge. There is a manual cable to open the charge port located on the inside of the driver's side passenger door frame

 

[alohart]

If the 12v isn't totally dead or unable to take a charge, it should charge up from the HV traction battery, if the car itself is plugged in to charge.

I believe this is a catch-22. If insufficient 12 V power exists due to a discharged or weak 12 V battery, the high-voltage system and DC-DC converter can't start, so the high-voltage battery pack can't charge the 12 V battery.

 

[Anonymous]

I believe this is a catch-22. If insufficient 12 V power exists due to a discharged or weak 12 V battery, the high-voltage system and DC-DC converter can't start, so the high-voltage battery pack can't charge the 12 V battery.

Yeah, that's the caveat - has to be enough of a charge left in the 12v for the car to initiate the 'handshake' between the car and the charge source and start charging.

 

[jadnashuanh]

To get into the vehicle, you may have to resort to actually using the key. To get access to the key slot in the driver's door, you have to use the key in a small slot underneath the handle to pry out the plastic cover, which should pop out, gaining access to the actual key slot. Once you're in there, you can use the manual controls to open the hood.

All of that is shown in the user's manual, and you can download an electronic copy if you don't have access to the physical book.

If the fob remote will open the door, there should be enough power in the battery to enable charging. If it isn't sufficient to fully activate everything, there's a phantom 12vdc charging path that, over time and if the battery can accept it, recharge the 12-vdc battery slowly versus the normal path of the DC-DC converter from the high voltage battery pack.

From what I've heard, depending on the MY and software version, you may or may not have to disconnect the HV while charging the 12-vdc battery. But, it's generally simple to disconnect the HV...sometimes, getting it closed again can be tricky, though.

 

[semimadscientist]

I'm curious as to experiences here. Just before leaving for a vacation, my 12V battery started going wonky (2015 i3 w/REX). So, I'm worried that it will be stuck when I get back home even if I leave it connected to the EVSE. I own a 12V charger, but not a trickle keeper. Would it be safe to just expect the battery to die and then goose it enough to get it running when I get home where it's first trip will be to the dealer to get the battery changed (already made the appointment)?

 

[EvanstonI3]

You would be better off disconnecting the negative lead to the 12v battery terminal while gone and then seeing the voltage when you return and then charging it separately to see if you can make it to the dealer. You just need a 10mm wrench and should be able access this without removing the FRUNK tray.
If you insist on leaving a failing 12v battery connected for an extended period of time, you risk it causing all sorts of errors that would need to be cleared if it failed while your car was just sitting.

If the 12v is failing, there is nothing you can do to prevent this or make it last longer.

As for charging while you are gone, the car will not allow the 12v battery's voltage to drop below 12.0 volts (normally 12.7-12.9).
The car will come on and boost the battery for one hour at a time in an attempt to keep the 12v alive, but if the battery is failed to the point of not being able to Hold a Charge, the car will apparently give up in this eventually.

 

[cdnji]

As for charging while you are gone, the car will not allow the 12v battery's voltage to drop below 12.0 volts (normally 12.7-12.9).
The car will come on and boost the battery for one hour at a time in an attempt to keep the 12v alive, but if the battery is failed to the point of not being able to Hold a Charge, the car will apparently give up in this eventually.

Learned something new today... Thanks!

 

[alohart]

As for charging while you are gone, the car will not allow the 12v battery's voltage to drop below 12.0 volts (normally 12.7-12.9).
The car will come on and boost the battery for one hour at a time in an attempt to keep the 12v alive, but if the battery is failed to the point of not being able to Hold a Charge, the car will apparently give up in this eventually.

Learned something new today... Thanks!

This seems to be something that wasn't widely known until recently when an i3 owner with a 12 V battery monitor installed noticed that when his i3 was parked, the DC-DC converter was charging his failing battery for an hour whenever the battery's voltage dropped to 12.0 V. A 12 V battery monitor (~$20 at Amazon) seems to be the best way to detect when a 12 V battery is gradually failing, so I installed one.

 

[Egbert]

This seems to be something that wasn't widely known until recently when an i3 owner with a 12 V battery monitor installed noticed that when his i3 was parked, the DC-DC converter was charging his failing battery for an hour whenever the battery's voltage dropped to 12.0 V. A 12 V battery monitor (~$20 at Amazon) seems to be the best way to detect when a 12 V battery is gradually failing, so I installed one.

I just received mine today. It will be installed sometime this week.

https://www.amazon.com/dp/B09W4R2L8P?psc=1&ref=ppx_yo2ov_dt_b_product_details