Video: Standard 9V Battery vs Model 3 Frunk

[markb1]

Here are some tiny 12V 23A alkaline batteries:

https://www.amazon.com/Powertron-23A-Alkaline-Battery-Pack/dp/B002B8SOFM

I wonder how many amps are required to close the high voltage contactors?

Edit: Actually, think "23A" might refer to the form factor, not the amperage. But still, I wonder what it really takes to close the contactors?

 

[MarkS22]

I was referring to the possibility of keeping a jump starter in the frunk, and use a 9V to get into the frunk to retrieve it and to access the car's 12V terminals.

I don't think you necessarily have to charge the car's 12V battery. The jump starter could provide enough power to close the contactors that enable the high voltage system, which would then allow the car's 12V systems to run off the DC-DC converter. You might be able to drive it with a completely dead 12V battery.

Gotcha. We’re on the same page. The question is how big a battery is required to close the contacts? I’d imagine it takes less than starting a “2.5L gas engine.”

But do you really just need to connect the high voltage? What about the various computer systems?

 

[mwu]

If the frunk is open, can you manually close the latching mechanism for the frunk without actually closing the frunk? I assume the latch is similar to a car door on most cars where a metal loop is on one side and the latch is on the other. The latch can be manually closed on the door without actually closing it (but don't close the door / frunk with the latch already closed)

If so, you could disconnect the 12V battery and with the frunk still open, flip the latch, and use the 9V to release the latch thereby solving the question as to whether the 9V will do the trick even with a dead 12V battery without potentially locking yourself out of your car.

 

[insaneoctane]

@MarkS22, you perfectly answered the question I was after in this thread:
If your 12V battery dies....
I will keep my 12v jumper in the frunk. It's quite small. Now, thanks to you, I know hiding a 9v is one solution. We need to get you an A123 12V to try! Now if Tesla fixes the frunk to NOT open when standard 12V is present we have a real winner!

 

[MarkS22]

@MarkS22, you perfectly answered the question I was after in this thread:
If your 12V battery dies....
I will keep my 12v jumper in the frunk. It's quite small. Now, thanks to you, I know hiding a 9v is one solution. We need to get you an A123 12V to try! Now if Tesla fixes the frunk to NOT open when standard 12V is present we have a real winner!

23As will be here on Monday with small alligator clips/wires to solder on each end.

 

[markb1]

Gotcha. We’re on the same page. The question is how big a battery is required to close the contacts? I’d imagine it takes less than starting a “2.5L gas engine.”

But do you really just need to connect the high voltage? What about the various computer systems?

I agree. Doesn’t seem like it should take much.

Assuming the DC-DC converter is functioning properly, once the HV contactors are closed, the converter should power all of the 12V systems. At least, that’s my theory.

 

[MarkS22]

I agree. Doesn’t seem like it should take much.

Assuming the DC-DC converter is functioning properly, once the HV contactors are closed, the converter should power all of the 12V systems. At least, that’s my theory.

My thought is, for safety reasons, a computer would need to boot first. For example, to make sure there are no error conditions and the main pack is in a safe state... and then it closes the connector. Normally, this probably happens very quickly because the system is awaking from a sleep state. Just speculating... there are probably others here who understand the process more.

 

[MarkS22]

A true and trusty pioneer, you are! Huh, I wonder if it's using a boost from the 12V and that if the 12V was truly dead you'd have to have hook up a 'proper' supply?

It also quickly brings me to the question, can I set up the frunk opening to alert me on my phone. Because the 'kids' are surely going to get wind of this very quickly.

EDIT: Another question occurred to me. When you made sure the phone was off had you left the car alone long enough to enter the full sleep mode, I think 5 min or something people are reporting?

P.S. Is your car ever dry????

Regarding “full sleep mode,” I believe so but I can’t be 100% as I didn’t intentionally wait a specific time. I can say the mirrors folded, the doors were locked, and the charging cable was locked. I specifically checked to make sure the car wasn’t allowing any access. If we’re talking about securing valuables, shouldn’t it work under the same circumstances as the door locks and charging cable? Doesn’t seem right to get “more secure” a few minutes after you leave. But, could testing the handles have reset the sleep timer? Totally possible.

After opening the frunk, I even went back to check that the doors/charging cable were still locked. Just to make sure nothing strange happened that authenticated access to the car. Everything remained locked.

I’m not particularly concerned about security. I’m actually pleasantly surprised that smaller, more readily available batteries may provide access. It’s likely Tesla will check for 12V in future versions/firmware, so it’ll be more secure than the S/X.

 

[RyanS]

Great find.
I am wondering if 23A would fit into that space. Just tape 23a battery with wires and store it inside of that pocket.
What about 5V? If 5V works then any USB power/port could open frunk

 

[K-MTG]

Regarding full sleep mode...so when you walk away from the car (you hear a click). The car is in sleep mode after the click occurs. I found the car alarm isn't active until you hear the click...the alarm only sirens after the click occurs (when you open the door). The click occurs on my 3 within 3 minutes but sometimes it takes a bit longer if my phone is close by (or I lock the car with the key card) instead of walking away with my phone.

 

[RayK]

This thread reminds me of when I discovered how easy it was to unlock the door of 1st gen Mazda RX-7s without a key. No damage was done, no scratches, nothing left behind that could indicate how the car was unlocked, didn't need the use of a slim jim or any other potentially incriminating tool. Just a simple, long screwdriver. After some practice, it took me about 5 seconds to open the locked door. This information was imparted to me at one of the early RX-7 owner conventions around 1981. Somebody then designed a metal baffle that could be installed inside the door which prevented this technique from being used.

Note that this meant access to the interior of the car so it was much worse than what @MarkS22 has discovered. I hope that Tesla is reading all of the information discussed in this thread and can implement the appropriate fix ASAP.

 

[Dr. J]

So, with all the discussions about the Model 3's 12V frunk opening system, I thought it would be interesting to see what would happen if you didn't use a 12V portable jumpstarter... but rather a standard 9V alkaline battery.

Sir, you're a steely eyed battery man--Battman!

 

[arnis]

I thought it would be interesting

Don't be so sure
Tesla Model 3 Down: Won't Power Up, and is Inaccessible

Jump starting whole vehicle requires more amps. As there will be initial load from modules BEFORE
contactor will engage.
Keeping 12V7Ah block with comfortable alligator clips (faston terminal one end, alligators another end, AWG8 wire inbetween)
closeby AND spanner for dead battery terminal release should be enough for every situation.
Start the vehicle with this one and then, without disconnecting, connect back negative main terminal to dead battery.
Jump starting with main battery connected is likely NOT possible.

This one costs 10-20 bucks. And can give a 100Amps for 5 seconds. That is enough for everything EV has.
Even a smaller one would work but as they are more rare, price goes up Pointless.

This battery requires trickle charging twice a year.

EDIT: I think ultra-mega-cool-looking vehicle jump starters use that same battery. They are huge and cost way more.

 

[navguy12]

Don't be so sure
Tesla Model 3 Down: Won't Power Up, and is Inaccessible

Jump starting whole vehicle requires more amps. As there will be initial load from modules BEFORE
contactor will engage.
Keeping 12V7Ah block with comfortable alligator clips (faston terminal one end, alligators another end, AWG8 wire inbetween)
closeby AND spanner for dead battery terminal release should be enough for every situation.
Start the vehicle with this one and then, without disconnecting, connect back negative main terminal to dead battery.
Jump starting with main battery connected is likely NOT possible.

This one costs 10-20 bucks. And can give a 100Amps for 5 seconds. That is enough for everything EV has.
Even a smaller one would work but as they are more rare, price goes up Pointless.

This battery requires trickle charging twice a year.

EDIT: I think ultra-mega-cool-looking vehicle jump starters use that same battery. They are huge and cost way more.

arnis: could you provide a simple schematic of what you propose please? Thanks.

 

[mongo]

Start the vehicle with this one and then, without disconnecting, connect back negative main terminal to dead battery.
Jump starting with main battery connected is likely NOT possible.

I would recommend against procedures that require live reconnection of the main 12V battery. If everything goes fine, it will probably work, but if you knock off the alligator clip while moving the negative terminal, it may spike the 12V similar to alternator load dump (actual results depending on DC-DC regulation, total system load, etc).

Given that jump packs can start dead ICE cars, why would they not be able to start an EV? (Or are referring to trying to start off only a 9V battery?)

 

[arnis]

but if you knock off the alligator clip while moving the negative terminal, it may spike the 12V similar to alternator load dump

Likely not possible. DC-DC converter is not able to raise voltage like alternator (old alternator, voltage regulated alternators don't do that).
It's like disconnecting laptop from the brick while laptop is being charged. There is no voltage spike on brick side.

arnis: could you provide a simple schematic of what you propose please? Thanks.

Disconnect black from car battery. Connect jump alligators to red terminal (which is still connected to dead battery) and black terminal (which is floating in air). Start the car. Connect that floating terminal back to vehicles battery. Without disconnecting alligator clip.

 

[mongo]

Likely not possible. DC-DC converter is not able to raise voltage like alternator (old alternator, voltage regulated alternators don't do that).
It's like disconnecting laptop from the brick while laptop is being charged. There is no voltage spike on brick side.

All DC-DC converters have a frequency response limit on their control loop. Any step change faster than that response will cause a voltage rise due to inability to instantly change the control point. Additionally, (unless there is a secondary overvoltage protection) the energy in the output inductors will cause a voltage overshoot.
In the case of alternator, the field control cannot reduce the current from 100A to 0 as quickly as the the battery terminal can be disconnected.
In the case of a laptop brick, the supply us designed to handle the overshoot involved (or it has a first break signalling pin to initiate shutdown).
The intermittent connections made when reconneting the dead 12V battery might even be worse than a single small battery disconnect event.

 

[⚡️ELECTROMAN⚡️]

Turn on security alarm feature and when your frunk gets popped open when you’re not around. You’ll be notified by the app and by loud blaring sounds.

Also in jersey. My 3 haven’t been dry since I bought it.

Have you experienced this with the MS?

 

[MarkS22]

Don't be so sure
Tesla Model 3 Down: Won't Power Up, and is Inaccessible

Jump starting whole vehicle requires more amps. As there will be initial load from modules BEFORE
contactor will engage.
Keeping 12V7Ah block with comfortable alligator clips (faston terminal one end, alligators another end, AWG8 wire inbetween)
closeby AND spanner for dead battery terminal release should be enough for every situation.
Start the vehicle with this one and then, without disconnecting, connect back negative main terminal to dead battery.
Jump starting with main battery connected is likely NOT possible.

This one costs 10-20 bucks. And can give a 100Amps for 5 seconds. That is enough for everything EV has.
Even a smaller one would work but as they are more rare, price goes up Pointless.

This battery requires trickle charging twice a year.

EDIT: I think ultra-mega-cool-looking vehicle jump starters use that same battery. They are huge and cost way more.

I don’t know how many amps it needs to reboot all the systems and close the high voltage connector. Nobody is going to have a battery capable of jump starting the vehicle readily available outside their car. I thought a 23A or 9V could be hidden/attached on the exterior used solely to pop the frunk to gain access to a larger battery.

 

[arnis]

Yes. But having a small 12V 7Ah battery nearby is doable. Like somebody proposed, why not keep it in the frunk. With the spanner and clip on wires of course.
If money is not a problem, one can buy this expensive box. Compared to lead acid battery, it weighs less.
And it might work without main battery disconnecting.
https://www.amazon.ca/Multi-function-MoKo-Portable-Emergency-Flashlight/dp/B01N40PZI5

Me personally, I will just take cables. There are people around me with their cars. I can ask for help.