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12V battery access and location

VerityZooms

Member
Apr 19, 2016
131
108
Chicago, IL
So, I've found these two ‘battery posts’ (at least, for jump-starting the 12V system) under the service panel, in the frunk — strangely, they're on *opposite sides* of the car, nowhere near one another:

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However, I need to attach power-leads specifically at the point where the 12V battery grounds to the chassis; does anybody know where, within the body of the car, the actual 12V battery is mounted / located?

(In that vein: is there an easy way to remove the interior lining of the frunk? I need to mount a transceiver package to the inside-edge thereof, and I'd like to remove the lining before I drill any mounting-holes.)
 
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VerityZooms

Member
Apr 19, 2016
131
108
Chicago, IL
Okay, so I'm … mildly concerned again. Maybe I'm overthinking this, but,

  1. This is a battery under load — I haven't found a way to truly turn the Model X off? Unless I'm missing something, the doors always operate, the screens light up immediately when you sit down / the computers are obviously always running, etc etc etc. Thus, whenever the circuit is closed with the battery, there's going to be some current.
  2. I can't get to the actual battery to detach the negative lead from the battery's post in one motion; instead, as shown in the pictures above, I'm going to be fishing the negative lead (currently attached to the chassis), out past … a ton more chassis. With a metal tool.
  3. If (when) the lead, or my tool, or anything, touches any part of the chassis, then unless I'm very confused, the battery's circuit is going to close again, probably causing current-draw from whatever electronics are always-on in the car? If it touches parts of the chassis multiple times on the way out, I'm effectively applying and killing power to the car's electronics over and over? Right?

Has anybody actually disconnected the 12V in a Model X, and could speak up as to their experience? I'm super-paranoid about this now.
 

VerityZooms

Member
Apr 19, 2016
131
108
Chicago, IL
@VerityZooms, did you ever make progress on your efforts in this thread?

I'm considering accessing the 12V system for another purpose, and would love to hear anything you learned along the way.

Yep! Got sparks, car shut off, I was overly scared, everything was fine when I finished and reconnected it.

Just remember that since the accessible terminals in the X are not the actual battery posts, but rather the opposite end of the battery's leads, you need to reverse the traditional wisdom of the battery (disconnect the hot lead from the battery's hot terminal first). The goal, of course, for anyone reading along, being to avoid creating a short-circuit across the chassis if you slip and drop whatever lead you disconnect first … traditionally, if you disconnect the hot lead from the battery, and you drop it, you either drop it against the chassis (where the negative-lead is already grounded, thus doing precisely nothing), or back onto the battery-post, which merely has the effect of restoring the normal, non-shorted circuit. (Not great for the electronics; but also a lot less bad than an exploding lead-acid battery, amirite?)

However, since we don't have access to the actual battery, then if we're holding the other end of the hot-lead, and we drop it, it has the opposite effect: if it touches any part of the chassis (or worse, some unfused electronics' terminals), then there's a short-circuit: +battery → +lead → chassis (or worse, an expensive piece of electronics) → −lead → −terminal. Do not want! Instead, you disconnect the negative lead from where it attaches to the chassis (see photos above) first; in this case, your worst case, dropping that lead anywhere within the chassis, is again simply resuming the (properly fused) circuit. Secure that lead well, so it cannot come into contact with the chassis, before beginning work on the positive lead's attachment to the distribution box.

Not as ideal as disconnecting directly at the battery, but waaaay easier than trying to get access to it.

Apologies if that's obvious to you; just recording it for posterity coming across this thread.




I've already had to do this twice, and am looking forward to installing two more systems on the 12V bus (thank you, 2500W DC-DC converter! ); so I'm going to disconnect it one last time and install a RigRunner, and further installation or reconfiguration can be done in a moment with Anderson PowerPole plugs (and properly fused ) … without fiddling with the Tesla's distribution block or battery leads again. lol.
 
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ohmman

Upright Member
Global Moderator
Feb 13, 2014
10,436
19,346
North Bay, CA
No, that was not immediately intuitive to me, but it makes perfect sense.

So I'm also looking to install Anderson Powerpole connectors capable of attaching 1/0AWG cables to cover something like a 50A draw off of the 12V bus. Have you found the DC-DC converter to be adequately sized for your draw?

Mind sharing what your project is? Looks like possibly ham radio related?
 

Dazureus

Member
Jan 9, 2015
335
396
Michigan
I can't get to the actual battery to detach the negative lead from the battery's post in one motion; instead, as shown in the pictures above, I'm going to be fishing the negative lead (currently attached to the chassis), out past … a ton more chassis. With a metal tool.

Why can't you access your 12V battery? My 12V battery is just to the left of the drivers side fuse box near the frunk and it looks like the positive terminal is on the left and negative on the right. Couldn't you just disconnect it there?
 

VerityZooms

Member
Apr 19, 2016
131
108
Chicago, IL
Why can't you access your 12V battery? My 12V battery is just to the left of the drivers side fuse box near the frunk and it looks like the positive terminal is on the left and negative on the right. Couldn't you just disconnect it there?

… in the Model X? Are you talking about the distribution-block (big array of fuses, pictured at the top of this thread with the positive-lead's terminal circled), or is yours just laid out totally different from mine?

Mind shooting a photo?
 
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Dazureus

Member
Jan 9, 2015
335
396
Michigan
… in the Model X? Are you talking about the distribution-block (big array of fuses, pictured at the top of this thread with the positive-lead's terminal circled), or is yours just laid out totally different from mine?

Mind shooting a photo?

The Atlas BX is the battery and mine is just to the left of the distribution block you reference.
 

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