Permanent 12V Aux Battery connected to 12V car Battery. Will it work?

[globile]

So I forgot to plug in the car before applying a software update. 5 hours later, car was dead. Something wonky with the update (2020.20.17). This is a 2018 Model X, with 2.5 years and 70K km.

Jump starting was effective, but not immediate. I had to "revive" the old battery for at least 20 min with the jump start cables, before I could get enough life back from the battery to open the charge port.

The "12V battery must be replaced soon" message shows, but it disappeared only to come back again (after a deep reset).

Tested the battery voltage and it shows a constant 11V, so definitely gone bad.

So, the issue is I have a 10 hour ferry trip ahead of me, and I won't be able to plug the car in. It will be idle with no cell coverage.

I have an auxiliary 12V (60Ah) battery, that I was thinking of connecting to the old battery.

Will this provide enough juice to the systems (and old battery), so I can start the car after the trip?

The other option I was thinking of, was to enable Camper mode, and hope it doesn't drain the battery pack past the 20% mark over the 10 hour period.

Anyone had any issues like this?

Thanks!

 

[jmaddr]

I don’t get it. Why not just replace the 12v? I’m guess it’s not available quickly enough for your ferry trip? There is nothing magical about the Tesla 12V other than its smaller than most since it doesn’t have to provide cranking amps.

 

[globile]

I don’t get it. Why not just replace the 12v? I’m guess it’s not available quickly enough for your ferry trip? There is nothing magical about the Tesla 12V other than its smaller than most since it doesn’t have to provide cranking amps.

Yep, Battery is not available at the moment. Searched for a similar battery to the atlasbx 60B19RS that Model X carry, even if just temporary, but it has to fit exactly or I'd have to put it somewhere else.

Also, access to the model X battery is not exactly a 5 min job so wanted to avoid that if possible, but yes, that would be the ideal solution.