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Video: Standard 9V Battery vs Model 3 Frunk

Discussion in 'Model 3' started by MarkS22, Feb 23, 2018.

  1. MarkS22

    MarkS22 Member

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    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.

     
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  2. ℬête Noire

    ℬête Noire Active Member

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    A true and trusty pioneer, you are! :D 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???? :p
     
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  3. favo

    favo P3D+ owner

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    Yeah, if OP is feeling brave, try disconnecting the car's 12V battery and see what happens.
     
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  4. MarkS22

    MarkS22 Member

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    That's an excellent question. If the 12V was truly dead, could the 9V open the frunk to do a proper jumpstart? Maybe, maybe not. But I think it's important for everyone to know about this, either for personal security or in a pinch. If the 12V had some power left, it's possible it could still open it without needing a full jumpstart.

    Hah... it's never dry during this time of year in New Jersey.
     
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  5. gregincal

    gregincal Active Member

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    Yeah, definitely don't want to be leaving anything valuable in the frunk.
     
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  6. MarkS22

    MarkS22 Member

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    The sole use for this would be to open the frunk. I think the concept of using the portable 12V jumpstarter is that you use it to open the frunk and then recharge the main 12V battery. This would only be useful to open the frunk and then you're stuck again.

    I suppose this would allow you to keep a portable 12V jumpstart battery in the frunk? Then you just need a 9V somewhere on the exterior of your car and you never have to worry. In theory, because we don't know if a 9V would work if the 12V is completely drained.
     
  7. favo

    favo P3D+ owner

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    The idea was to see what would happen if the 12V battery in the car were depleted. Rather than trying to abuse your battery, I suggested you just disconnect it. Of course, the battery would be present and connected in most cases. I guess the disconnected battery may not be a good substitute for depleted battery, though, if the electrical connection from front bumper relies on the battery being there somehow. Only one way to find out. :eek:
     
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  8. MarkS22

    MarkS22 Member

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    A couple notes:

    (1) I did use a multimeter to ensure those jumper cables weren't somehow supplying 12V. It turns out they're they read less than 9mV. The 9V battery I used was registering at 9.22V. I just wanted everyone to know I am taking precautions.

    (2) A standard alkaline AA battery did not open the frunk. The AA I used was outputting 1.623V. So, clearly the frunk needs more than 1.6V. Furthermore, it's some evidence that it doesn't use the existing 12V to supplement the power requirements to open the frunk.
     
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  9. ℬête Noire

    ℬête Noire Active Member

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    If you don't have at least a 12V trickle charger and the 12V battery is dead you aren't gaining much opening the frunk.....unless you store the trickle charger in there...but why, and that's a lot of baggage to pack around for very rare edge-case benefit.
     
  10. Jays200

    Jays200 Member

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    I keep my Noco GB70 in the frunk too BUT the Model X has a manual emergency frunk release, unlike the M3's.

    We are driving our MX the 4000kms across Australia (hopefully the first MX and a proper family vacation) in June/July and this coincides with the 12v battery dying and the keyfob batteries simultaneously going flat ;) Our first supecharger will be 2600kms from our start point and I don't know about Tesla's response time to a break down on the Nullabor.
     
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  11. ℬête Noire

    ℬête Noire Active Member

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    #11 ℬête Noire, Feb 23, 2018
    Last edited: Feb 23, 2018
    Yeah, I was thinking maybe it could be two potential paths with one a MOSFET relay signal line that's gating the 12V battery supply. A 9V should be able to drive that no problem, the lower voltage AA not enough.

    Then it's got a NOT gate that fails-open a path in the case of a completely dead onboard 12V that can directly release driving from that front port. Still sounds plausible when I type it out? *shrug*

    Something gets crossed up in the communications between the engineers and the documentation writers, you end up with that incorrect entry in the manuals.

    ---

    That it's just a low power required latch is also possible, of course.
     
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  12. MarkS22

    MarkS22 Member

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    After I had a (rare) 12V battery failure due to a firmware issue, it got me thinking: What's the easiest way to open the Model 3 frunk in an situation like you're describing... where Roadside Assistance or other cars might not be nearby. If it means keeping a 9V in your pocket and a 12V charger in the frunk for those long trips, I feel this technique could be useful.

    Personally, I like the idea of it opening with such a common, tiny battery. As you note, the S/X have manual pulls to open the frunk, so it's not like this is a security concern if you're aware of these facts. I suspect Tesla would have the ability to monitor voltages and update the firmware to (1) require more than 9V to open the frunk and/or (2) prevent the frunk from opening if ~12V is detected from the battery like the manuals describe.

    Let me be clear: Absolutely nothing I'm discussing here gives you access to the main cabin or the car itself. This only opens the frunk. Most people were concerned about this "electrical" frunk mechanism, so I see this as a positive.
     
  13. PoitNarf

    PoitNarf My dog's breath smells like dog food

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    Thanks for testing this! Very interesting stuff. As someone else mentioned it would be great if the Tesla app alerted you when the frunk is forced open like this. I can totally see a market for a little 9V kit that can be securely and discretely affixed to the underside of the Model 3 somewhere for emergencies.

    And I definitely consider myself warned that nothing of value should be stored in the frunk!
     
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  14. markb1

    markb1 Active Member

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    A portable jump starter isn't a lot of baggage, these days. This one is will crank a 6.5L ICE:

    https://www.amazon.com/DBPOWER-18000mAh-Portable-Starter-Charging/dp/B01D42TYFC/

    For a Model 3, it should require much less current, so you could get away with something even smaller.
     
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  15. MarkS22

    MarkS22 Member

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    I have a DBPower and they're great little devices, but they're still not small enough to keep outside your Model 3. They're also not great for temperature extremes. This whole thread started with the thought of "What's the smallest, most convenient way to open the frunk in the event of a 12V power problem?"

    In my original frunk opening demos, I specifically used the:
    https://smile.amazon.com/gp/product/B074WM8855

    This one is 8000mAh for a "Gas Engine up to 2.5L" However, I don't know how much is required to get the Model 3's 12V battery back up from a discharged state to one where the car can be turned on.
     
  16. YauKwan

    YauKwan Member

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    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.
     
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  17. chojn1

    chojn1 Member

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    Very good info to have!
    Now can you open the glove compartment without power?
     
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  18. PoitNarf

    PoitNarf My dog's breath smells like dog food

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    Has anyone tested this? And yes, sick of all of this rain NJ as well...
     
  19. markb1

    markb1 Active Member

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    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.
     
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  20. Jays200

    Jays200 Member

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    No, but you can't in any Tesla vehicle ATM.

    That's what the booster is for. Once you've accessed the frunk you then connect the booster pack and that powers up the car 12v system which, amongst other things, allows you to release the electric park brake for towing, gaining access to the car cabin and using the MCU and other essential car features.
     
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