A Tesla Model 3 has two batteries, and the name on the side of the car does not tell you which one failed. Knowing the location of each one tells you what kind of help to call for. If the 12-volt died, you need a jump. If the traction pack is empty, you need a mobile Level 2 charge. If you are reading this from a Denver shoulder, call (720) 738-6950 and we will match you with an operator who quotes before any cable goes in.

The two batteries, in one sentence each

The traction pack is the big one. It sits under the floor of the car, flat between the front and rear wheels. That is the battery the trip meter reads in miles. It is also the battery a Supercharger or a Level 2 stall fills.

The 12-volt battery is small and ordinary. It sits under the hood, near the front of the car, behind a plastic trim panel. It runs the computers, the contactors, the door locks, the lights, and the touchscreen. It is not what moves the car. It is what wakes the car up.

The two batteries do not swap jobs. The pack cannot start the 12-volt. The 12-volt cannot move the car a single inch. When a Model 3 looks completely dead, one of them has failed, and the symptoms are different.

Why the 12-volt is the one that strands you

The traction pack is heavy, sealed, and managed by its own thermal system. It shrugs off cold Denver nights. The 12-volt is a small lead-acid or lithium-ion brick that loses voltage when the temperature drops. Park the car at DIA for a week in January. Park it in a Highlands Ranch driveway through an arctic blast. Park it on a Wheat Ridge street for a long weekend. The pack may still show 60 percent. The 12-volt will read low or flat when you come back.

When the 12-volt dies, the car looks identical to an empty pack. Touchscreen dark. No clicking. Doors will not unlock from the handle. The mobile app shows the car asleep and will not wake it. A bystander would call it a dead EV. The owner calls it a dead EV. Tesla calls it a dead EV. Mechanically, it is a small battery that needs a jump or an on-site replacement.

This is why a Tesla 12V jump is its own service and not part of a charge. A charge fills the big pack under the floor. A jump wakes the 12-volt under the hood so the car can wake itself up.

Where the traction pack actually is

The traction pack is the long, flat module that runs the length of the floor pan. You cannot see it without lifting the car, and you should not lift it on a shoulder. What you can see is the charge port, which is the small door on the rear driver-side taillight. That is the only place a charge cable connects. The cable feeds the pack through an onboard charger, which converts AC to DC before it fills the cells.

A mobile Level 2 source brings 240 volts to that port. Tesla drivers get a native NACS plug on the lead. The operator connects the cable, the car wakes up on its own once it sees the power, and the pack begins to take a charge. That is the whole procedure on the outside. There is no flap under the car to lift, no panel to remove, no special tool the operator needs beyond the right plug.

Where the 12-volt actually is

The 12-volt sits at the front of the car, under the hood, in the frunk well. To get to it, you open the hood. On most Model 3 years the hood releases from inside the car or through the mobile app. On a dead 12-volt, neither works. The mechanical release is a loop of wire or a small panel at the front of the car, just below the nose. Pull it. The hood pops a quarter inch. Lift it.

Once the hood is open, the 12-volt is under a plastic cover near the firewall. Two cables come off the terminals, one red and one black. Those are the same kind of posts you would jump on a gas car, smaller and closer together.

The operator connects a portable lithium jump pack to the posts, waits for the car to wake, then disconnects. The car’s own DC-DC converter will recharge the 12-volt from the traction pack once everything is running. The whole sequence takes minutes when the 12-volt is the problem.

If the 12-volt is too far gone to take a jump, the operator can swap one on site. That is a different job, still under the hood, still not a charge.

Which battery actually died, from the driver’s seat

The simplest tell is the gauge. If the dashboard showed 20 percent or 5 percent or zero before the car stopped, the pack is empty. A mobile EV charge is the right call. If the car showed normal range and then would not wake, the 12-volt is the suspect. A jump is the right call.

Cold weather scrambles the tell. A pack that read 50 percent at 70 degrees may read 30 percent at 5 degrees. The car may also refuse to start in cold weather even with a healthy pack, because the 12-volt is sluggish. That overlap is why so many cold-morning no-wake calls turn out to be the 12-volt and not the pack.

A second tell is the accessories. If the doors unlock, the lights come on, and the touchscreen shows the Tesla logo, the 12-volt is alive. The car is awake. If the screen is dark and the doors will not open, the 12-volt is the problem.

A third tell is the app. If the Tesla app shows the car as awake and charging, the pack is taking a charge somewhere. If the app shows the car asleep and unresponsive, the 12-volt is likely dead.

What an operator brings to a Denver shoulder

Charge Pro DEN matches you with an independent local operator. The operator carries a portable 12-volt jump pack and a mobile Level 2 source. Both pieces of gear fit in a single van. The operator confirms which battery the car needs before quoting, and the quote is a number you hear out loud before any work starts. The operator bills you directly for the work performed.

For the pack, the cable adds 10 to 20 miles of range in 15 to 30 minutes of charging. The clock starts when charging starts, not before. That is enough range to drive under your own power to a Supercharger or a home charger. For the 12-volt, the jump takes minutes. If the 12-volt needs to be replaced, the operator can do that on site as well.

If the car needs a tow instead of either, the operator will say so. A bent suspension, a body-on-frame accident, or a pack that will not take a charge at all are tow jobs, not rescue jobs.

Where this matters in the Denver metro

The Capitol Hill apartment dwell is the most common Denver call. No home plug. A cold morning. The car will not wake. That is a 12-volt failure nine times out of ten, and the traction pack still has range. The parking-garage no-wake pattern looks the same in the Tech Center and at the Anschutz campus in Aurora. Long dwell, marginal battery, dark screen.

The I-70 climb from Golden is the other shape. A driver who left town at 80 percent watches the gauge drop on the grade. By the time they hit the Idaho Springs Supercharger they may have 8 percent or less. That is an empty pack, not a 12-volt failure. A jump does nothing. The right call is a charge to a usable margin, then drive to a stall.

The DEN airport lot call runs the other way. A traveler leaves the car for a week. Returns to a dark car. The pack still shows a normal state of charge in the app. The 12-volt is dead. The right call is a jump, not a tow to a stall.

What to try before you call

A few minutes of work can save a service call. Confirm the car is actually asleep, not just slow to wake. Try the Tesla app. If the app shows the car awake, the problem is something else. If the app shows the car asleep and will not wake it, the 12-volt is the prime suspect.

For a 12-volt, the mechanical hood release under the nose of the car is the only path when the electronic release is dead. Pull it. Once the hood is open, do not jump the car yourself unless you know which posts to use. A jump on the wrong terminal will damage the car’s electrical system. The right posts are the small 12-volt posts under the hood, not the orange high-voltage cables that run through the pack.

For an empty pack, the right move is a Level 2 charge to the rear charge port. Make sure the port is unlocked. If the port is stuck or frozen, that is a different problem. A stuck charge port needs the latch released before any cable goes in.

If neither a jump nor a charge solves the problem, the car needs a tow. A Tesla cannot be towed with the drive wheels on the ground without risk of damage. A flatbed is the only safe option. AAA, Tesla roadside, and a local tow operator can all dispatch a flatbed. For the full split, read AAA, Tesla, and a local mobile rescue.

When to call Charge Pro DEN

Call (720) 738-6950 when the car is on a shoulder, in a driveway, or in a parking lot, and you cannot tell which battery died. An operator will talk through the symptoms with you. If the symptoms point to a 12-volt, an operator with a jump pack can be on the way. If the symptoms point to an empty pack, an operator with a Level 2 source can be on the way. The operator quotes before any cable goes in. You pay the operator directly.

Charge Pro DEN is a referral line. We match you with an independent local operator. We do not own trucks, employ technicians, or set prices. The operator does the work and bills you for it. The phone number is the matchmaker, not a promise of an arrival time.

If the car is in a travel lane or another unsafe position, call 911 first. Stay in the car with your hazards on if that is the safer choice. CRS 42-4-1202 covers a disabled vehicle on a highway shoulder, and hazard lights must be on under 42-4-230.

Frequently asked questions

Where is the Model 3 12-volt battery?

The 12-volt sits under the hood, near the firewall, under a plastic trim panel. It is the small battery that runs the touchscreen, contactors, and lights. The traction pack is a separate, much larger battery under the floor.

Where is the Model 3 traction pack?

The traction pack is the flat module under the floor of the car, between the front and rear wheels. The only place to charge it is the rear driver-side charge port. A Level 2 cable feeds the onboard charger, which fills the pack.

Can I jump the Model 3 12-volt myself?

You can, with a portable lithium jump pack and the correct posts. The posts are under the hood, not the high-voltage orange cables. If you are not sure which posts to use, call an operator. A jump on the wrong terminal can damage the car’s electrical system.

Does a mobile charge fill the traction pack?

A mobile Level 2 charge adds 10 to 20 miles of range in 15 to 30 minutes of charging. That is enough to drive under your own power to a public stall or a home charger. It is not a full charge. The operator confirms the added range before quoting.

What if the car will not wake after a cold Denver night?

A cold-soak no-wake is almost always a 12-volt failure, not an empty pack. A jump or on-site 12-volt replacement is the right call. The traction pack may still show normal state of charge in the Tesla app.

What if the gauge showed low range before the car stopped?

An empty pack is the right diagnosis. A mobile Level 2 charge is the right call. A jump on the 12-volt does not help because the 12-volt is not the problem.

Does Tesla roadside handle the 12-volt?

Tesla roadside can dispatch help for a 12-volt failure on a covered plan. Coverage varies by year and plan. Confirm in the Tesla app before you wait. The operators we refer handle the same job for drivers who want a quote first.