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I am curious. What is charging the 12V battery in P8? Is it charged from the main Li-Ion battery or only while driving?
 

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What is charging the 12V battery in P8?
According to the user manual (under the topic "Jump starting using another battery"):
Under normal conditions, the 12 V battery is charged when the vehicle is charged, and through electrical current transfer directly from the high-voltage battery when the vehicle is not plugged in for charging.
I interpret this to mean it's constantly charging from the high-voltage battery - both when the car is plugged in for charging, and when not.
 

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Speaking from personal experience w/ my recent Model 3:

If the 12V battery dies, nothing else works - can't start the car, can't charge the car, can't put it in tow mode to drive it onto the transporter going to the repair shop, can't communicate with it (no cellular or WiFi signal reception) etc. This little unassuming 12V battery is the real jewel in the crown that must be protected at great costs, which means no boosting other cars, no charging any device that might put a kink in this delicate balance of power. period.
 

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If the 12V battery dies, nothing else works - can't start the car, can't charge the car, can't put it in tow mode to drive it onto the transporter going to the repair shop, can't communicate with it (no cellular or WiFi signal reception) etc.
Not sure about Tesla, but our Volvo user manual says we can jump-start the 12V battery if this happens:
Jump starting using another battery | Starting and switching off vehicle | Starting and driving | XC40 Recharge Pure Electric 2021 | Volvo Support (volvocars.com)
 

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Not talking about jump starting, which is permissible with Tesla too. It's boosting another vehicle that's the caveat.
As the owners manual says on that page from your link:
"The charging points of the vehicle are only intended for jump-starting the vehicle in question. The charging points are not intended for jump-starting another vehicle. Using the charging points to start another vehicle could cause a fuse to blow, which would cause the charging points to stop working."
 

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Not talking about jump starting, which is permissible with Tesla too. It's boosting another vehicle that's the caveat.
You're certainly correct - you can't jump-start other people's cars. I wasn't debating that, sorry if I gave the wrong impression.

I just wanted to make sure people were aware if your 12V battery has died, you are not totally screwed: you can jump-start your 12V battery from another car.
 

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has anyone one tried using a lithium battery brick that you can use for jump starting an ICE car?
 

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The "car 12v battery" in both the Tesla and the Volvo XC40 EV are smaller than normal ICE car batteries. They are also a bit "hidden" in the front Frunk area and not easily accessible. And that is I believe done for a reason. THEY DON'T WANT YOU USING THEM TO JUMP START OTHER CARS. They are smaller since there is no "starter" motor to spin a gas/diesel engine. They are charged from the EV batteries. And yes, if you know how, ,you can access them and use a charger or jumper battery to "charge" them back up in case they are drained and your EV car won't start.
 

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Didn't realize this and jumped my neighbors car this morning. It was fine, just took a while to get through the frunk. I guess I won't be doing that anymore.
I now have 2 EV cars, Volvo XC40 & Tesla X. Neighbor needed a "jump" so I took over my good ol battery charger and that makes more sense. Nothing to remove in the Frunk to get to a battery that is TOO small to properly and safely do the job. But I believe you could probably have your car "running" and connected to put some charge into another car's battery. I just would not like to have them connected when the other car is "starting up." Not only is it a large draw on your 12v battery there are extraneous voltages, spikes, etc that possibly could come from the other car and possibly affect your XC40 "computer systems."
 

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Tesla and Nissan state that using an electric vehicle to jump start a gas vehicle will void the warranty. It is not recommended.
 

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The "car 12v battery" in both the Tesla and the Volvo XC40 EV are smaller than normal ICE car batteries. They are also a bit "hidden" in the front Frunk area and not easily accessible. And that is I believe done for a reason. THEY DON'T WANT YOU USING THEM TO JUMP START OTHER CARS. They are smaller since there is no "starter" motor to spin a gas/diesel engine. They are charged from the EV batteries. And yes, if you know how, ,you can access them and use a charger or jumper battery to "charge" them back up in case they are drained and your EV car won't start.
I need to check with service, but on volvocars.com if you pull up the 12V battery specs for the P8 and say a T5, they are identical 760CCA and 70aH.

 

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Speaking from personal experience w/ my recent Model 3:

If the 12V battery dies, nothing else works - can't start the car, can't charge the car, can't put it in tow mode to drive it onto the transporter going to the repair shop, can't communicate with it (no cellular or WiFi signal reception) etc. This little unassuming 12V battery is the real jewel in the crown that must be protected at great costs, which means no boosting other cars, no charging any device that might put a kink in this delicate balance of power. period.
Exactly what happened to me suddenly and without any good reason. Car was 4 months in my possession with about 4000 miles. Shop found a defective 12V battery. Replaced and so far so good. Maybe the battery should be tested every so often.
 
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