Tesla to Tesla power cable (jump start)

Tesla to Tesla power cable (jump start)

It would be nice if a Tesla can think of a cable that let Tesla owners give power from their cars to other Teslas that need power. Something similar to a jump start cable on ICE cars. Say a Tesla vehicle battery is dead but they know someone with another Tesla or they have another Tesla at home. Someone can give electricity from their Tesla to charge the battery of the Tesla with a dead battery using a special cable. Maybe there is a limitation I'm unaware of but I thought the idea can be useful now there are more and more Teslas out there.

EVRider | November 14, 2018

Unless you are really careless, you’ll never have a dead main battery in an EV.

jimglas | November 14, 2018

@EVR: iranout of gas in my Prius, twice. Chit happens, as does careless and stupidity.

GHammer | November 14, 2018

It's way more complicated than just having a cable. There would need to be a DC-DC converter in line to regulate the charge rate. High current DC-DC converters are very expensive.

DTsea | November 14, 2018

not going to happen.

Vawlkus | November 14, 2018

Impossible for a layman to do safely, and I say that as an electronics engineering technologist.

jolov | November 14, 2018

I agree with @EVRider. This is just completely unnecessary.

After 60K+ miles (half in a short-range LEAF, half in an S), I've never come close to needing such a thing.

Tesla2018 | November 14, 2018

So that means if someone has free supercharging and anyone person doesnt then the one car could suck free electicity from the other car? They should make it and call it the Tesla Tapeworm.

EVRider | November 14, 2018

@jimglas: It’s easier to run out of gas in an ICE car because you don’t have to plan as carefully, and you can generally get up and running again quickly. EV’s take more planning, and the cost of making a mistake is much higher. In theory, a car that runs out of gas could siphon gas from another car, which is analogous tonwhat the OP proposed, but in practice I’ve never seen that happen on the road.

Yodrak. | November 14, 2018

"Something similar to a jump start cable on ICE cars."

Not a proper analogy. The ICEV analogy to an EV running out of charge would be a syphon to move gasoline from one car's gas tank to the other car's gas tank.

syclone | November 15, 2018

A jump start is probably not possible without a lot of equipment. A tow start is possible and has been demonstrated. A one mile tow gives 10 miles of range.

jimglas | November 15, 2018

@sy: That is interesting

GHammer | November 15, 2018

It's impossible that 1 mile of towing gave 10 miles of charge.

jamesguan117 | November 15, 2018

You misread that. He drove an additional 10 miles before giving up.

“The Tesla was towed for 1 mile, and he was then able to do 10 more miles of similar driving before giving up and driving home,”

wisam.alrawi | November 15, 2018

I'm not an electrical engineer so I really don't know how complicated that can be. I just was thinking of those USB power banks that can power your gadgets. Say a laptop can charge your phone via USB. I think of a Tesla Model S as a giant battery that can give power to another device (Tesla).

Donz_S | November 16, 2018

If it were a simple solution, it would be pretty neat to have (like Yodrak mentioned with syphoning gas for ICEs), but in reality it doesn't seem at all feasible. Towing on the other hand... Call AAA and ask them for a 1 mile tow! :-) | November 17, 2018

Ok, this comes up every 6 months or so over the last 5 years. It is a very expensive solution for a very rare event. I estimate it would add at least $1000 to the price of the car, and likely double that. You have to convert the 350-400 VDC from the source car to AC then back to DC. You can skip the last step, since the car already has a AC to DC charger built in if you are willing to limit charging to about 30 miles/hour. Costs go up dramatically if you want faster power transfer.

The issue is to charge the lithium-ion battery it needs to be a very precise voltage/current - you can't just stick any old voltage to the battery. So your source car has a 100% SOC battery at 400V, and the drained car is at 340V. Numbers are illustrative, not exact. If you connected these two directly together both batteries would be quickly destroyed. Likely both cars would catch on fire too!

The equipment required would also add about 100 lbs to the car, so it would also reduce the EPA range of the car slightly.

So, yes it can be done, but I doubt many owners are willing to pay an extra $1-2K to help another stupid owner and get reduced range as well - for an event most will never see.

kichwas | November 17, 2018

Only example I know of an M3 going fully dead was on the “what if we try this” (or something like that” video series where the guys drove in circles around a supercharger station until the car died.

It took them a while past “0” to actually have the car fail.

NKYTA | November 17, 2018

@kich, “broder” is the term.

The ultimate in “fake news” before we had alternative facts.

Hit piece on the original MS.

wisam.alrawi | November 18, 2018

Thank you for enlightening me. Great points!
Certainly, it doesn't make sense to go through all this trouble for a rare case of dead battery here and there.

kichwas | November 19, 2018


No idea what that means. Video I an referring to is a series where the author posits a “what about this” question or takes them from viewers and then tests them. In this case folks wanted to know what it took to run out the battery to fully dead and how to recover. So after they drained it out, they had a tow truck tow them ti the nearby charger and then were back and running normally a few minutes later.

TabascoGuy | November 19, 2018

I think NKYTA meant "bricked" but had an auto correct slip through.

NKYTA | November 19, 2018

@Tabasco, bricked is what happened to the traction battery. Broder was the idiot that caused it.

saxxon | November 20, 2018

I think the practical way this would be done is with a portable battery pack. IE a Powerwall setup configured to fit in the back of a Tesla vehicle and then have a connector inside to plug into to directly power the system.

Problems are weight and cost. Weight, I think the Powerwall is listed around 250#s. Cost, not practical for the owner (who's going to bring it) but for a service company, you would bring the battery pack to the motorist, they would pay a fee and deposit and return the battery after they got to a charger.

Doable, not sure how often someone manages to get stranded.

TabascoGuy | November 20, 2018

@NKYTA, my apologies. Trying to read quickly is probably not a good idea here.

kcheng | November 20, 2018

I suppose the OP means like the movie In Time, a simple transfer, as opposed to a jumpstart. | November 20, 2018

To those who think it would be a major technical hassle to build a "jumper cable" for a Tesla... well I *am* an electrical engineer and while I am not expert at power electronics it is not hard to do the job. When you plug into a 240 volt, 90 amp wall connector there are no smarts in that cable. The power converter and charge controller is in the car being charged. The only thing needed is to generate AC from the battery DC. That's the solution I understand the best and if Tesla has provided for the battery to provide power to the charge port it would be fairly simple.

Then it might not be a big deal to go one step further and provide direct DC power to the car being charged. There are pretty beefy power controllers in the car already and Tesla may have already provided for this... or not. Can't say since they haven't shared the design with me. But even if it would only be on new cars with a new design for the battery electronics, it is likely that this could be provided as well.

But as some say, don't run out. Bjørn Nyland showed a video where they had to jump the 12 battery on a car before they could unlock it to tow it on a flatbed to a charger. lol Nothing was easy that day. It went dead because the owner parked it with 30 miles left and the night cold caused the range to drop to where it wouldn't keep the 12 volts up. Norway!

NKYTA | November 21, 2018

"well I *am* an electrical engineer and while I am not expert at power electronics"


"When you plug into a 240 volt, 90 amp wall connector there are no smarts in that cable"

Which cable? The UMC? Maybe it isn't smart, but "no smarts"??

"Then it might not be a big deal to go one step further and provide direct DC power to the car being charged. "

Yep, no big deal.

With such a lofty username comes great responsibility...

DTsea | November 21, 2018, the 14-50 is AC. the car has no AC output.

Yodrak. | November 21, 2018

"I *am* an electrical engineer and while I am not expert at power electronics ..."

Thankyou for admitting that you don't have expertise in the issue at hand. It saves us from wasting time reading the rest of your post.

SO | November 22, 2018

If you are that concerned about running out of charge, take a generator with you. | November 22, 2018

I'm actually an electronics engineer and I know a bit about the Tesla. See my response above. There are no hidden electronics in the car to do this, and it will requires a lot of additional expensive electronics. More importantly, there is really zero need for it.

Let's put this in the perspective of a gas car. How many people carry a gas siphon hose (maybe $5?). Now how many people do you see that have run out of gas on the road - can't say I've seen anyone in the last 10+ years. I'm sure it happens, and I'm willing to help someone, but it's not worth it to spend $5 for something I've never in my life have ever needed. Now consider there are at least 1000 times more ICE cars than EVs today on the roads. As others pointed out, It's a very expensive solution looking for a problem.