I literally just moved my 2016 MX 90D on the driveway to charge another car. Tried getting back in the X, it unlocked but the door didn’t open. I can’t access it on the app either as it’s just loading. Went over to the front and these lights are on and red. What does that mean? I can’t find anything online about this.
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Help! What does this mean??? (PIC)
- Thread starter jdsalinas
- Start date
The LV battery is necessary to "wake up" the HV battery. Once the HV battery is awake and enabled it supplies 12v to the car systems/LV battery, and the car can operate as normal. At that point you can take the 12v battery out and you should be fine until you park and let the car go back to sleep. After which point you wouldn't be able to wake it up without jumping the LV system.
But even there, it seems that Tesla detects the failing LV battery and keeps the HV battery awake when the car would normally be sleeping, which is why it gives the message that it will consume more energy when idle.
Of course, things can go wrong, so I'm not sure I would continue to drive it, other than one way to get the LV battery replaced, without a jump pack handy.
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Not quite true.
Back story with my MX:
I jumped the dead 12V. Everything booted up as normal. I pressed the brake pedal to close the door. The screen said "Unable to drive...etc" when shifting to D and proceeded to shut down immediately.
The next day, mobile tech came out, jumped it, and was able to shift to D.
One astute poster made the observation that I pressed the brake to close the door, whereas the mobile tech did not do so before shifting gear (driver door was open).
What happened was after jumping the 12V battery, the car booted up, but the DC-DC contactor had not engaged to charge the 12V. It would only engage when the car is truly "on" like when you shift to D. By pressing the brake to close the door, power was used and drained it of all juice required by the DC-DC contactor to engage. So it shut down again.
This DC-DC contactor is not always on. It only engages to charge the 12V battery when the 12V battery's voltage drops low enough. The 12V battery is of course being used to power all electronics in the tesla. If you somehow remove the 12V battery while driving, chances are the DC-DC contactor is not engaging at that point in time, and all electronics will immediately go black.
This is also the reason why the 12V battery in a tesla dies so fast (1-2 years.) It has to withstand deep discharge cycles, whereas an ICE 12V gets continually charged while the engine is running.
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No, absolutely true. I said "Once the HV battery is awake and enabled it supplies 12v to the car systems/LV battery," just opening the vehicle doesn't wake up the HV battery. That requires either "starting" the car, or starting to charge the HV battery.
That sounds like your jump pack didn't have enough capacity to close the door and wake up the HV battery at the same time.
The DC-DC is enabled/operating anytime the HV pack is awake. So, when the car has been started or is charging. It doesn't cycle on and off while you are driving, it supports the 12V load the entire time the car is driving.
But it is charged anytime you are driving. However, it is a much smaller battery than what a typical ICE vehicle has, and it is of a deep-cycle variety to account for it use differences. (And they do last more than 1-2 years for most people.)
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Mine is 3.5 years old and, fingers crossed, hasn't presented any problems.
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I stand corrected. The HV contactor/DC converter remains on whenever the car is "on".
The issue that I had was the auto-closing-on-brake door while jumping the car. The jump pack charged the 12V enough to power everything on, but closing the door caused voltage to drop again, which didn't allow the HV contactor to engage. So it's best to shift to D to engage the HV contactor/DC converter immediately to allow 12V charging after jumping.
TMC is full of posts with people's 12V lasting 1-2 years using the old lead acid. Both my older MXs had to have replacements in about the same time frame. The new lithium type is lasting much longer.
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And just to clarify, mine is lead-acid. I believe climate can be a big factor in 12v longevity... hot climates cause them to die faster. Also, the lithium batteries are 16v, right?
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Are you saying you disconnected the jump pack before you tried to "start" the car? Yeah, I wouldn't do that, just like you don't disconnect the jump pack from an ICE vehicle until after you have started it.
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Correct me if I’m wrong but I think it might depend on just how much juice your dying 12v has left. I jumped mine and disconnected it before I “started” the car and it didn’t die again. Although I was prepared and drove around with my jumper pack in the frunk, I also had no further issues as I drove it 2 more days before mobile came and replaced it.
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