Finally discovered something that Tesla Model S cannot do. Jumpstart another car

Finally discovered something that Tesla Model S cannot do. Jumpstart another car

My daughter's needed a jumpstart and my wife took the jumper cables from her and tried to put them in the Tesla so I could go. We both laughed at the same time.

mrspaghetti | April 2, 2013

Ironic, isn't it? That a car with that much electrical potential can't jump start such a relatively small thing as an ICE battery :)

herkimer | April 2, 2013

Doesn't Model S has a 12v battery? not accessible to connect jumper cables?

mbcaffe | April 2, 2013

there is a 12v battery. no idea where it is.

GeorgeA | April 2, 2013

Perhaps Tesla could design a modified jumper cable that would plug into the wall adapter end of our charging cable and the other end into the charge port. This would only work if power could then be pulled from our batteries through this modified cable to start someones car. A software option that we would select for this may have to be added if this would even be possible. It would make it fairly easier for us to then given someone a jump vs trying to find and hookup the 12v battery we also have. It is ironic that we cannot offer a jump now. Tesla may address this as time allows in the future.

Tâm | April 2, 2013

There's a private thread on how to steal your perfectly good Model S with its perfectly good 12 V battery. That's not the header but that's the discussion.

If you read it, instead of stealing it, you can EASILY access its 12 V positive post (clip negative clamp on chassis.) The instructions & pictures are quite clear and vivid.

However, your Tesla is too expensive so I wouldn't advise to mess around with it. It's cheaper to fry your portable $50 Jump Starter than your Tesla :)

Brian H | April 2, 2013

The TM 12V is small, like a motorcycle battery.

derek | April 2, 2013

The 12v battery is on the right side of the frunk near what would be the conventional firewall location. But it is not designed to be user-accessible.

Tâm | April 2, 2013

You can see Tesla Model S left Red Positive and right Bare Negative lugs are VERY much easily accessible.

kashiraja | April 2, 2013

It probably not designed to jumpstart a car! :) Normal car batteries are bigger because of all the amps needed to crank the engine initially...

Curious why they even put a battery in there when a DC-to-DC would be sufficient to supply current to the various 12V electronics and ventilation.

Tâm | April 2, 2013


If you only rely on 1 single power source from the propulsion battery, then when you broder it down, there is no way to power up that power source to get it recharged!

It is good to have separate power systems in case something goes wrong like a driver who refuses to plug in and tries to broder it down.

A Tesla Ranger can show up to the rescue and can easily wake up the the car's control systems with the 12 V and thus allow to plug in to recharge the propulsion battery.

This is not a new concept. It has been proven since the defunct GM EV1 days.

nickjhowe | April 3, 2013

The Model S battery is 35Ah, so almost a full 'normal' car battery; not a motorcycle battery.

info | April 3, 2013

I'm not sure this would work, but..... I have a jumper cable that attaches from cigarette lighter to cigarette lighter. It was supposed to eliminate the necessity of getting dirty or worse from attaching jumpers directly to the battery. The downside was that it had to be left in the socket for 15 minutes. It was so useful that I can't find it now, don't remember if I threw it out, have no recollection of it ever starting any car and have a general feel that it was a waste of money. That being said, I think they're still being sold and they must work on something. Come to think of it, I've bought a lot of stuff that didn't exactly live up to my expectations. That feeling has been completely reversed by Tesla.

jat | April 3, 2013

@info - you can't get much current out of a cigarette lighter without blowing the fuse, certainly not enough to power the starter in the other car. So, sounds like they are charging the other car's battery for 15 minutes at a lower rate, which may or may not be useful depending on the problem in the other car. Personally I would rather just use jumper cables (but I agree the Model S isn't a good source for that either).

shop | April 3, 2013

It's been a long while since I had jumper cables. Instead I have something like this - they have versions that include a tire inflator, which would at least be useful for the Tesla.

gasnomo | April 3, 2013

Not true if you use one of those jumpers that works by plugging into cig lighter

Brian H | April 3, 2013

The lugs are also useful for jumpstarting the MS if the 12V goes flat; a booster battery can sit in the frunk and stay hooked up while you maneuver it to a Service Center or the like.

SMOP | April 15, 2013

Just replaced the garbage 12v battery that comes standard in the Model S with a Odyssey. Hopefully the problem is not with the undersized dc to dc converter that Tesla has been using in the Model S. This replacement should at least mask the low voltage issues for a few months/years before another replacement.

shop | April 15, 2013

@SMOP - What low voltage issues?

Velo1 | April 15, 2013

Damaging your Model S trying to jump start someone is revolting.

dstiavnicky | April 15, 2013

If you connect to the wrong batteries the other car will get flipped onto its roof!

patp | April 18, 2013


It's the second time my 12V is dead. Did you replace the OEM battery yourself? What were your issues prior to that?


herkimer | April 18, 2013

I picked up one of these awhile ago:

Works like a charm for jump-starts and flats. There are cheaper units available. Has come in handy several times.

rkang | April 18, 2013

The Model S is designed NOT to help ICE cars. hahahaha

Pungoteague_Dave | April 18, 2013

You absolutely can jump start a car or anything else 12-volt with a Model S. Pop off the nose cap and hook up to the color coded 12 volt studs. I started a dead ATV last weekend with our Model S.

shop | April 18, 2013

Maybe an ATV, but you are risking drawing too much current trying to jump start a car. I believe the manual tells you not to do this.

Brian H | April 18, 2013

An ATV's engine takes a lot less cranking power than a car.

Vawlkus | April 19, 2013

I suppose this means Model S is not backwards compatible :P

rlk | March 22, 2014

@SMOP Ur replacement battery working out for you?

Koz | March 23, 2014

As others have said, you can jump another car with the Model S. In fact, I had to jump start my wife's Volt with our S. Not easy to pop off the nose cone to get to it but it can be done.

Pungoteague_Dave | March 23, 2014

I jump started our diesel F-250 yesterday using the Model S. One of our employees left the truck with an empty trailer at a local boat ramp, ran the boat five miles around to our property and took an ATV back to get the truck - oops, key still in ignition, engine off, ignition on, dead battery. He called me and I took the S and jumper cables over to the truck, popped the nose cone, hooked up and it started right up.

The deep cycle batteries in the Model S are regular car batteries and there is no reason that they cannot be used to jump an ICE. Brian's comment above that they are smaller motorcycle-size batteries is incorrect. I dug around and found mine behind a panel in the frunk area. Normal, full-size battery.

Tesla does not advise doing this, but it does work. Your mileage may vary...

Mand | May 17, 2014

How is this 12v battery charged? Only when plugged in, or is it charged from the main batteries as well?

sule | May 17, 2014

Well, jumpstarting obsolete ICE cars will soon be obsolete because everyone is going to go buy Teslas and other EVS.

Other than that, when one ICE car is to jump another one is usually supposed to have the engine of the "donor" car running to provide additional power source. This is partly because more energy is needed than in a "normal" crank - powering both cars electrical systems, staring one and charging its dead battery for a short while (while connected).

hammy16 | May 17, 2014

In reality I believe you probably could jump start another car with a model S. If you remove the nose cone and
attach to the large 12 volt posts. The Tesla 12 battery is about half the size of a regular car battery
but no different than a number of "portable" jump starters available. Not sure how much current protection is in the Telsa battery connection and would also be worried about feeding back charge current when the ICE engine starts. Not for the faint of heart however..

Roamer@AZ USA | May 17, 2014

You can jump start from the front terminals but I would only do it in an absolute emergency. The Current Tesla lead acid battery is 1/2 the size of a normal ICE start battery. When the car is turned on 12 volt is supplied thru a DC to DC converter. I highly doubt that this converter is rated for the cranking amps demanded for normal ICE engine start.

Took this picture of a new 12 volt ready to be installed a few weeks ago at the Scottsdale service center. It is half the size and half the amp rating of a normal automotive start battery. IT IS NOT A FULL SIZE ICE CAR START BATTERY.

I put my hand in the photo for scale. It's a cute little guy and about half the size of a traditional ICE start battery. It is not rated for engine starting. The battery does not even have a cold cranking amp rating. It's a small deep cycle.

Roamer@AZ USA | May 17, 2014

Here is the data plate on the 12 volt battery currently being installed.

Roamer@AZ USA | May 17, 2014

Here is a catalogue listing of standard automotive start batteries and a few deep cycle batteries. The lowest rated battery listed here is twice the amp hour rating of the Tesla 12 volt. The battery in a Tesla is not a full size automotive 12 volt.

You risk damaging your battery and DC to DC converter if you use your Tesla to crank a ICE engine. You can do it but you are severely over taxing what the battery is rated to do.

Buy a portable jumper battery and don't kill your Tesla. High probability you will have a bricked car if you smoke the DC to DC power supply by drawing to many amps cranking an ICE engine. There is a reason automotive start batteries have a CCA rating for starting engines.

Roamer@AZ USA | May 17, 2014

Posted more info in this thread to clear up this weird myth that the Tesla 12 volt battery is a standard ICE 12 volt battery. It is not.

Roamer@AZ USA | May 17, 2014

I learned a lot just over one year ago when my week old Tesla died twice in one week due to 12 volt battery problems. This was back when the excide batteries, that were the size of a motorcycle battery, were failing. The replacement lead acid is just a little larger but still 1/2'the rating of a full size battery.

The car died and Tesla jumped it and drove it to service to replace the battery. A few days later it died so hard we could not even get it to power up with the Service guys portable jumper battery. I happened to have a portable jumper battery that was much larger than the service guys battery. We were finally able to power it up just long enough to get it into neutral with the brake off so it could be pushed out of the garage. Then loaded it onto a flat bed tow truck. The car didn't even have permanent license plates yet.

All this happened in the first thousand miles over one year ago. Have not had an issue since and received the current 12 volt, like the one pictured in a post above, during a later service visit.

I think the 12 volt failed first and over loaded the DC to DC converter. So the car lasted until the new battery went dead and died hard the second time. All this is ancient history and the incidence of 12 volt failures effecting customers seems to be under control.

But then people jumping cars with their Tesla are just a bricked car waiting to happen. It is not a start battery and the converter that charges it is not rated for high amp cranking loads.

Buy a portable jumper battery if you want to jump start things. If you can afford a Tesla you can afford a jumper battery.

Brian H | May 17, 2014

Thanks for that; I got reamed for saying it was half the size of a standard 12V! But I don't think you can brick more than the 12V itself by overloading it. The car would be mobile again as soon as you replaced the 12V.

Roamer@AZ USA | May 17, 2014

Brian, the scenario on my car a year ago was the battery from the bad batch of batteries died and overloaded the DC to DC converter. Back then the trouble shooting was not what it is today. They replaced the battery but the fried DC to DC converter was toast so the car lasted until the new battery went dead. At that point it was really dead. Took over an hour of jumping to finally get it to,stay on just long enough to get neutral and brake off. I have to admit it was a little scary to have all that happen in the first 1000 miles.

But life has been wonderful ever since. Also the Tesla guys that came to the house were more concerned about the problems than I was. I had to keep telling them it was fine I could drive my other cars. They were great to work with.

Roamer@AZ USA | May 17, 2014

Brian, Not sure who started the rumor that the battery is a full size automotive. Specs are specs. It's not difficult to look at the specs and determine the battery size.

Here is the spec for a Harley Davidson Electro Glide Battery

30 amp hour rating. The "upgraded" larger Tesla is now 36 amp hours. Who ever keeps saying its a full size atomotive battery never bothered to look at the specs.

It is a little less than half the rating of an automotive start battery and by no means appropriate for jump starting regular ICE vehicles unless you want a bricked car.

SongWhistler | May 18, 2014

Very informative thread!

A simple question -- please forgive my blank slate mind -- are there any circumstances when I would use a portable jump starter to jump charge the 12 V Battery in Model S itself? I like the look of the portable jump starter/compressor linked above...

It sounds like there might be, say to enable safer flat-bed loading in some circumstances...Roamer, you used one so I guess the answer might be "yes but improbable..." Do I have this about right?

I'm trying lo learn how an EV works and how to own one, envisioning various scenarios and how to handle them while waiting for delivery of my Model S. (P85, MC red.). I haven't yet seen an MS up here where I live in the mountains of Western NC...seems likely to draw attention...if someone needs a jump, I'd like to be able to oblige.



Thomas N. | May 18, 2014

Good question WEBnNC. I have one of those Costco portable compressors/jumpers with some huge initial cranking capabiliy. I used it for jumping my ICEs and have helped out a couple of neighbors here and there.

I'd like to store it in the frunk (it is a tad heavy) and be able to jump the Model S should it ever need it.

Roamer@AZ USA | May 18, 2014

WEBnNC, I don't see any reason to haul around a 12 volt jumper battery. If the little 12 volt on the car fails or runs dead for some reason you can jump the car thru the front terminals and once powered up it activates the DC 2 DC converter that provides 12 volt power from the main battery and also recharges the small 12 volt.

Last year there was a flurry of 12 volt issues, myself included. Tesla replaced the batteries, improved the monitoring systems and eventually modified the car to allow installation of the slightly larger 36 amp hour battery that is currently installed in the cars.

If you were ever in a situation that you needed to jump start the car systems you are also in a situation where the car needs to go in for service right away. Something is likely wrong or failing.

I would expect if you jump start other ICE cars with your Tesla you really increase the probability of a failed battery or damaged DC 2 DC converter. It would be like taking a motorcycle battery hooking it to a small battery charger and then using the two to crank a ICE engine starter motor. You may get buy a few times but sooner or later the battery charger or battery or both are going to short out and die. Been there done that.

Roamer@AZ USA | May 18, 2014

WEBnNC, I was a little unclear in the first sentence of my last post. You can jump the car if the 12 volt is dead. But I think it will be extremely rare that you would ever need to. Also if you did need to the car needs to go in for service, something's wrong.

Based on where Tesla buried the battery and located the emergency jumper terminals it should be pretty obvious they didn't plan on using or servicing them very often.

3-G | May 18, 2014

A different twist on utilization of the 12 volt jumper terminals located behind the nose cone (Tesla service says if you pop the cone use a plastic flat tool to do so). I have a Costco portable air compressor which has battery clips, not a cig lighter adapter. I asked the Tesla service folks if I could attach the clips to the jumper terminals to inflate a tire on the Tesla in an emergency situation. Answer, not necessarily recommended but it can be done with one caveat: keep the Tesla running by being seated in the drivers seat which will run current from the main battery through the 12 volt. I presuppose that the same advice would apply to jumping from the Tesla 12 to another battery.

NKYTA | May 18, 2014

@3-G, thanks for asking Service! That was my supposition (someone in drivers seat with foot on the brake).

Roamer@AZ USA | May 18, 2014

If you do a google search for DCS 33 size batteries you will find the primary uses are mobility scooters and UPS backup power systems. They are not a full size automotive battery. If you wouldn't jump start a car with a mobility scooter then don't do it with your Tesla. Unless you want to be a pedestrian.

Pungoteague_Dave | May 19, 2014

I have started several cars and an F150 with the Tesla. We routinely use it to start motorcycles and ATV's that inadvertently get left off their tenders for some reason. No issue in a pinch. I discussed this with the local service center and was told "not recommended, but probably can't hurt anything unless you short it."

Pungoteague_Dave | May 19, 2014

BTW, I was guilty of spreading the incorrect "full size" size info, as that is what I was told by the technician who did my first deep cycle 12-volt upgrade. Sorry.

My Kubota 4wd diesel tractor has a 33AH battery and it works just fine to start that puppy. Not good for routine use, but that is plenty to start most cars or small trucks.