12V battery

[Mini2nut]

The good news? The 12v battery location was moved to a better location around 2016 on the Model S.

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[ajdelange]

It is indeed much easier to access it in the later ones. Disconnect the frunk LED connector, pull off a couple pieces of trim, undo a dozen bolts (with a power driver_, lift out the tub nd there it is.

 

[Red61224]

Of course I have no idea as to where the battery will be in the CT. In other Teslas it is in the frunk - well behind the frunk actually. To get it out you have to remove several bits of plastic surrounding the frunk rim, then take out a dozen bolts and remove the frunk (its a tub). At that point the battery is pretty accessible held into place with typical hardware. There should be You Tube videos on how it's done.

As for longevity: as you may know there have been problems with short lifetime of the 12 V battery. Some owners have replaced the lead acid stock battery with a Li ion battery made by Ohmu. Quite expensive but the surprising thing is that the warranty is only 3 yrs - not that much better than what one gets out of a good lead acid.

Thanks A.J.
I looked it up. $439.

https://www.ohmmu.com/

Decent warranty

Warranty | Tesla | All Models - 12V Battery
Warranty Terms

• 4 Years (48 Months) from Date of Purchase (no receipt necessary)
• 100% Full Replacement Coverage on performance failure of any sort
• Physical damage or use outside of intended purpose voids warranty

Warranty Claims
To file a warranty claim, please contact us via web chat or send an email to: [email protected]

Please be sure to include description of the problem, approximate purchase date, purchaser name, and address along with any relevant photos.

• Replacement units are approved within 24 hrs of claim receipt and shipped within 24 hrs of approval.
• Original unit must be returned using the return label and packaging included with the replacement unit. If old battery is not returned within 14 days, you will be billed to payment on file for the replacement unit
• Adapters are not included on replacement units and should be saved.

Ohmu
2604 W 1st St, Suite 42
Tempe, AZ, 85281
USA

 

[ajdelange]

Can't say whether they have added a year or if I just remembered it wrong.

 

[Red61224]

That's all that is required to swap the battery in the MX. Now as noted earlier you have to take out the frunk to get to the point where you can see those parts.

If you want to replace with the Ohmmu they certainly are.

I have seen some ICE cars where you had to remove a tire to replace the battery. Oh what fun.

 

[android04]

To anybody concerned about the work involved in replacing the 12v battery:
The early Model S was a pain because the 12v battery was buried underneath some electronics at the corner of the firewall. It was redesigned later and now it's easier to get to them on Model S and X. The best news is that on Model 3 and Y it's extremely easy. You open the frunk, pop off two plastic trim pieces, and use a 10mm wrench to loosen 1 bolt for the battery bracket. That same 10mm wrench loosens the battery posts. The vent hose that connects to the top of the 12v battery easily pops off.

 

[Friday]

ICE vehicles with ESS (electronic start-stop) have a second smaller battery paired with the normal battery. When the ESS battery fails or goes weak, it causes all kinds of problems, including not restarting the vehicle when it comes to a stop at an intersection. And there's no real monitoring system for ESS battery, so you have 2 batteries to worry about failing. I run with my ESS turned off due to the unreliability of the system.

 

[JBee]

It's unlikely 12V will go anywhere soon, as it is the defacto standard supply voltage for motherboards, on which FSD and most of the automation and entertainments runs in a Tesla. AS CPUs get faster the voltages get lower, so there will be at least 3-400W with of power required at 12V to run just this at full power.

There was some talk decades ago to switch to a 48V system for auto electrics, but this was mostly driven by an integration of mild hybrid vehicles (like the original Honda Insight), and of course driving peripherals directly from 48V, like HVAC, power steering, Air suspension etc. Now with higher voltage EV taking the stage, it's unlikely it will continue evolving to much.

As for Teslas "flex" wiring or whatever everyone is calling it, it won't eliminate 12V usage in a car, nor will it limit what voltages can be used. It's primary function is to reduce wiring harnesses in cars, by overlaying a comms signal to control devices on the same supply cable, without having to run separate cables to each. This means you can have say five lights on the same 2 core cable, and you can still switch each one individually. This is the same sort of thing you can do with a LAN over powerline adapter, where a data signal is superimposed over the power line voltage, and neither impacts the other (mostly).

 

[ajdelange]

It is possible to send power and signals over the same conductors as is done with the Dallas One-wire system (actually the signal IS the power in this case) or in the case of the Enphase system. But I would like to point out that in POE there are 4 pairs (green (data), orange(data), blue (power), and brown(power)). One pair carries transmit data, another receive data and the third and 4th the actual power.

 

[JBee]

It is possible to send power and signals over the same conductors as is done with the Dallas One-wire system (actually the signal IS the power in this case) or in the case of the Enphase system. But I would like to point out that in POE there are 4 pairs (green, blue, orange and brown). One pair carries transmit data, anothe receive data and the third the actual power. I don't know what the 4th pair is for.

LAN over power line is not the same as POE. Typically it digitally modulates a 2-50Mhz signal on the power line and then uses a high pass filter and demods it on the reciever end. There's quite a few standards for onewire, or comms over power in the microcontroller world which could be used for bus control over power in a vehicle.

 

[ajdelange]

No, it isn't the same. For example the Enphase system I mentioned puts the signal on a 240 VAC bus. Problem with those systems is they are low bandwidth relative to POE because they are piggybacking data on a power distribution system. But they can handle lots of power.

The auto guys seem to be intrigued with POE which is more than suitable for a camera or processor or modem which doesn't require much power relative to say a window motor which does not require much bandwidth. I think Lucid (?) is using ethernet in their cars. Or is it Rivian? Or maybe both. The 1000 base POE scheme uses each pair for two way signalling in differential mode and two of the pairs for power transmission in common mode. Can't send that much power through a pair of No. 18 in parallel but the connected devices need bandwidth and not so much power.

So I think we are going to see POE make its way into cars more and more. At the same time I think we will see windshield wipers, window motor assemblies, horns, lights etc. on a DC ring bus (or buses) which also carries the low data rate signals they need to control them.

Note: with DC you don't need filters. Isolating the AC data from the DC power is easily done with a cap (which I guess is actually a filter).

 

[Crissa]

https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_implementation

PoE uses higher voltage, and is what Tesla was discussing powering its components from.

The 12v battery doesn't power any of Tesla's big iron computers, it mostly powers the radios, which also can run on the higher (or lower) voltage.

But PoE doesn't eliminate the need for the auxiliary battery. They need it because converting DC voltage is inefficient unless you know the exact constant amperage of your load. So you can DC convert to power an LED no problem. To power a standby system? Not so good. To power a radio? Big problem.

-Crissa

 

[Diehard]

Thanks A.J.
I looked it up. $439.

https://www.ohmmu.com/

I used to have tons of battery problems on my motorcycle and wife’s scooter regularly and had to replace them frequently. It has been years since I switch to Li. I do not take care of these relatively cheap batteries at all and still zero problems. Highly recommend.

 

[Diehard]

Has any EV owner ever brought a dead or confused system back to life with a portable 12v jumper unit long enough to get home? Does it makes sense to carry a small one with you? What are your thoughts? I know not every battery is exposed and user friendly like ID4 but if you could get to it easily on CT, would you carry a 12V backup plan?

 

[ajdelange]

I haven't had to do it and fervently hope never to have to but my son gave me a little LiPo battery pack that comes with a set of jumper cables and the claim that it can start an ICE vehicle. Clearly the loads presented to the 12V battery aren't any where near what they are cranking an ICE machine so even this little battery should be able to do the job. All it has to do is boot the computer and let it run to the point that it closes the traction battery contactors which then energize the car's DC/DC converter which will run all the low voltage loads (computers, displays, lights...) thereafter. Now if the 12V battery has failed by shorting the DC/DC converter will not be able to maintain 12 V across it but while it is common for a cell to short the liklihood of all 6 shorting is small.

Now if you have one of these packs and remember to keep it charged and it has a "cigarette lighter" plug (which is one of the common ways of charging it, you ought to be able to pull off this "jump start" without having to take out the frunk simply by plugging into the cigarette lighter. It doesn't take much juice to run the computers and displays. If it is more than the cigarette lighter can carry its fuse will blow and you'll have to access the battery itself.

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