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"Voltage supply too low" error

whitex

Well-Known Member
Sep 30, 2015
6,825
8,671
Seattle area, WA
On a 2018 model S, does this error mean the 12v voltage or main pack voltage is to low?

I suspect DC converter is not working. How do I check it’s fuses? I can’t find them anywhere.

Thanks!
You will know real quick if your DC converter is not working, you 12V will be dead within few hours. Personally I think it's something else, did this error show up when plugged into a charger, or while driving?
 
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outdoors

.
Supporting Member
Aug 10, 2014
1,759
3,069
North Pole
I had this on a rental X in January. It subsequently stranded me and they had to come tow the vehicle. The 12v battery needed replacing.

Which is a good reason to proactively replace battery(not on rental). Another member recently chided my about replacing a "good" battery that had nothing wrong with it. Car has 100k miles. In the middle of nowhere I often find myself. Don't like to add the words stranded to that.
 

whitex

Well-Known Member
Sep 30, 2015
6,825
8,671
Seattle area, WA
Which is a good reason to proactively replace battery(not on rental). Another member recently chided my about replacing a "good" battery that had nothing wrong with it. Car has 100k miles. In the middle of nowhere I often find myself. Don't like to add the words stranded to that.
Have you proactively replaced you emmc or MCU for the same reason?
 
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outdoors

.
Supporting Member
Aug 10, 2014
1,759
3,069
North Pole
Have you proactively replaced you emmc or MCU for the same reason?

Oh so true. I have FSD. For my frame of ownership and the amount I don't use things I am good for a while. I don't really listen to music or stream stuff. I drive silent. Yes. Life of the party I know.

Tesla looked at it and cleaned out some crap. I don't believe it. I have yet to have any of the symptoms of MCU failure.

I plan on having them install my HW3 prior to the MCU infotainment upgrade. This would be screen #3 and obviously to MCU2. Basically the other way around the way they would like it(with my $2500)
 

mba83

Member
Jan 10, 2019
135
66
South Carolina
Would like to confirm: This message is about the 12V voltage level, and likely means the battery is going bad. In my case, it was because the on-board charger was bad (which disabled the DC-DC converter).

And FYI, if DC-DC converter fails, the car will turn off in minutes, not hours. The car pulls a lot of amps from DC-DC converter just to stay on.
 
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aerodyne

Nose cone car - to LR - 1-23 / 2-05?
Nov 19, 2018
3,723
6,051
Los Angeles
Must be a thing. Just got this low voltage error today. Car has not been driven in weeks. Noticed a car will not start error some time ago, which cleared. Then, high vampire drain and SMT showed the 12v being drained. Proactively changed the 12v, old battery tested and showed 33% loss of capacity. Everything was fine for a day, then the new batt started to get drained. Put it on a charger and still got errors, plus the low voltage, even though 12v on 10A charge, and 12.8v at the accessory socket.

Guessing the DC-DC converter is going which I guess means pulling the HV pack. Not happy on this low mileage, babied car.
 

whitex

Well-Known Member
Sep 30, 2015
6,825
8,671
Seattle area, WA
Must be a thing. Just got this low voltage error today. Car has not been driven in weeks. Noticed a car will not start error some time ago, which cleared. Then, high vampire drain and SMT showed the 12v being drained. Proactively changed the 12v, old battery tested and showed 33% loss of capacity. Everything was fine for a day, then the new batt started to get drained. Put it on a charger and still got errors, plus the low voltage, even though 12v on 10A charge, and 12.8v at the accessory socket.

Guessing the DC-DC converter is going which I guess means pulling the HV pack. Not happy on this low mileage, babied car.
With Tesla's updates trying to keep batteries from dying and/or catching on fire, my 2015 MS is running battery coolant pumps almost around the clock (in 70F degree weather my batteries are kept so cold that my regen is limited when I start driving!). Those pumps run from 12V battery and suck decent amount of power. That will exercise both the 12V battery and the DC-DC converter. Added stress will speed up wear, so more likely to push already aging components to failure. Up next, a surge of coolant pumps failing.

Welcome to Agile development - fix stuff as they start breaking, worry about what the fix breaks later, vs. comprehensive design and test. Works for software, not so much for hardware where damage cannot be undone via an OTA update. This is not the first time (think logging causing premature emmc wear, or permanently raising standard suspension height causing issues with drive-shafts - famous shudder problem), and probably not the last.
 
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aerodyne

Nose cone car - to LR - 1-23 / 2-05?
Nov 19, 2018
3,723
6,051
Los Angeles
@whitex...."Probably not the last"

You got that right. I won't charge above 78% unless I have too, to avoid wear on the pumps

Took me 24 years to buy another car. I rather fight back than cash in my chips.

Using SMT has been invaulable. Today I finished a mod bypassing the jump posts so I can keep the 12v at the optimum 13.6v, and lessen the wear on the contactors. Although, looks like they just went out...

First pic is the installation. Second is with the trim piece over it. Completely hidden, connector tucks away inside hood latch opening, and all parts can be removed without a trace should the car go to the SC...
15893346616391651283663896103515.jpg
15893349041665316060863220268192.jpg
 
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whitex

Well-Known Member
Sep 30, 2015
6,825
8,671
Seattle area, WA
I won't charge above 78% unless I have too, to avoid wear on the pumps
Aha! I think I just figured out Elon's plan here. People complained about capping battery range so that Tesla can avoid the 8 year warranty obligations, so instead Elon found a way to push the wear to non-warrantied parts. Basically, instead of capping you, you are presented with a choice, cap your own range or else the car will wear out the pumps, the contactors, and the DC-DC converter - none of which are part of the 8 year warranty. This also indirectly reduces your range since it increases the vampire drain, but guess what, vampire drain was never warrantied as part of battery degradation. As long as the battery charges to some % of original capacity, the fact that the car will chew through however many miles a day of that range running the cooling pumps is not considered battery degradation (even though indirectly caused by battery needing to be cooled so much).

Elon really is an evil genius.
 

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