How much 12v current is available?

AB4EJ · Mar 5, 2015

I am into amateur (ham) radio. If I would like to install a 2-way radio in a Model S...

Would there be 15 amps of 12-v available to power that radio while it is transmitting?

Would the 50 watts of RF coming out of the antenna pose a significant risk to the very complex Model S electronics? (typically 144 mHz band)

Does anyone have definitive (i.e., based on known facts rather than speculation) answers?

jgs · Mar 5, 2015

AB4EJ said:
Would there be 15 amps of 12-v available to power that radio while it is transmitting?

Would the 50 watts of RF coming out of the antenna pose a significant risk to the very complex Model S electronics? (typically 144 mHz band)

Does anyone have definitive (i.e., based on known facts rather than speculation) answers?

The 6.0 manual (p. 80) says "The 12V power socket is suitable for accessories requiring up to 15A or a maximum of 180 watts."

I doubt you'll find anyone able to answer your second question based on known facts rather than speculation -- even aircraft manufacturers don't seem to be able to provide definitive answers to such questions. If the car is susceptible to failure due to a 50 watt RF source nearby though, I'll be VERY disappointed.

scottm · Mar 5, 2015

AB4EJ said:
I am into amateur (ham) radio. If I would like to install a 2-way radio in a Model S...

Would there be 15 amps of 12-v available to power that radio while it is transmitting?

Would the 50 watts of RF coming out of the antenna pose a significant risk to the very complex Model S electronics? (typically 144 mHz band)

Does anyone have definitive (i.e., based on known facts rather than speculation) answers?

Curious where/how you would mount the antenna. Maybe placement matters. There are antennae all over the car for its purposes.

NigelM · Mar 5, 2015

Might be useful reading:

an-important-note-about-the-key-fob-and-RF-interference

Stuck-on-top-of-a-mountain-radio-frequency-issue-Car-won-t-see-the-key

AB4EJ · Mar 5, 2015

This might have been tried

jgs said:
The 6.0 manual (p. 80) says "The 12V power socket is suitable for accessories requiring up to 15A or a maximum of 180 watts."

I doubt you'll find anyone able to answer your second question based on known facts rather than speculation -- even aircraft manufacturers don't seem to be able to provide definitive answers to such questions. If the car is susceptible to failure due to a 50 watt RF source nearby though, I'll be VERY disappointed.

THANKS for the info on the current availability.
Regarding RF susceptibility - I worked as an engineer for GM years ago, and we had some RF chambers where we would bombard a running car (on the dyno) with all kinds of RF, to see what would affect it, and how. At the time, it took quite a strong RF field to affect a vehicle (way more than a typical ham mobile rig would produce); but the Tesla seems to have a lot more electronics than the cars I worked with. I was thinking that probably somebody has tried this and could provide actual test results.

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scottm said:
Curious where/how you would mount the antenna. Maybe placement matters. There are antennae all over the car for its purposes.

There are a couple of options. Several types of antenna are available with mounts to the trunk lid. Brave souls also will use heavy mag-mounts (risk here is scratching the paint). But what I really hope to do is to get a Model X with the trailer hitch; there are inserts that will let you put the antenna on the trailer hitch, with a tennis ball to help cushion it from banging into the back of the car.
Placement is a minor consideration. In the past, when I had a cheap car, I would drill through the roof and put a commercial antenna mount on, like on a police car or taxi, - this will give you your best RF pattern; but I wouldn't do this with a high end car - too much loss of value from the body damage. For casual use, you can mount an antenna almost anywhere; the car has enough metal mass to create your ground plane.

NigelM · Mar 5, 2015

AB4EJ said:
Several types of antenna are available with mounts to the trunk lid. Brave souls also will use heavy mag-mounts....
<snip>
For casual use, you can mount an antenna almost anywhere; the car has enough metal mass to create your ground plane.

You know the whole bodywork on Model S is aluminum...

FlasherZ · Mar 5, 2015

There are a couple of other things to note, if you don't want to use the lighter/accessory outlet. The nosecone terminals will give you up to 50A of current (it's protected with a dedicated fuse). However, you also have to mind the voltage... the Model S voltage can vary between 12 volts (static battery voltage, all powered down) and 15.1 volts (rapid charge cycle for the AGM 12V battery). Most equipment is built to survive this, but you should check.

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NigelM said:
You know the whole bodywork on Model S is aluminum...

The bumper and B-pillar have steel!

saladman · Mar 5, 2015

My intentions are to install the base unit of a Kenwood 700 in the Frunk, leaving me to install the faceplate in the interior. This should give me access to the battery terminals up front, leaving the 12v adapter free. And then a lip mount for the antenna on the back hatch.

The 2011 Nissan Leaf was not susceptible to any interference that I could find.

I've never drilled any of my cars for a radio install. Certainly not going to start here.

NigelM · Mar 5, 2015

FlasherZ said:
The bumper and B-pillar have steel!

Not sure either of those is good for a mag mount antenna!

herbvdh · Sep 15, 2015

Has anyone had any success installing a 2 Meter 440 Amateur Radio yet??? K2VDH I have heard that some Ambulance Squad member installed there Radio's but never found any solid info out.

AB4EJ · Sep 15, 2015

herbvdh said:
Has anyone had any success installing a 2 Meter 440 Amateur Radio yet??? K2VDH I have heard that some Ambulance Squad member installed there Radio's but never found any solid info out.

Diamond makes an antenna that can bolt (without drilling holes) to a typical trunk lid, so it would likely work on the MS hatch. Earlier in this thread, it is reported that plenty of current is available at the 12v battery terminals, but due to the fast charge circuit, it might be necessary to include a regulator in the circuit to protect the radio (these are readily available).

TaoJones · Sep 18, 2015

One can also draw from the battery (unswitched) via a dedicated connection with a (e.g., 15A fuse). Please keep in mind that the 12V console source is switched, meaning that it will shut off 30 minutes after the "Car Off" message appears.

Oba · Sep 19, 2015

The DC to DC converter is rated at 100 amps, therefore you could make a fused dedicated lime from the 12 volt battery to power your equipment.

What you need to know is how much power is actually available out of that 100 amps. Put an ammeter on the 12 volt battery, turn everything on (radio blasting, heater fan on full blast, all lights on, etc) and see what's actually burnt.

mspohr · Sep 19, 2015

NigelM said:
You know the whole bodywork on Model S is aluminum...

Aluminum works as well as steel for a ground plane. It does not need to be magnetic, just conductive.

markn455 · Apr 28, 2016

FlasherZ said:
There are a couple of other things to note, if you don't want to use the lighter/accessory outlet. The nosecone terminals will give you up to 50A of current (it's protected with a dedicated fuse). However, you also have to mind the voltage... the Model S voltage can vary between 12 volts (static battery voltage, all powered down) and 15.1 volts (rapid charge cycle for the AGM 12V battery). Most equipment is built to survive this, but you should check.

Where are the Nosecone Terminals located?

FlasherZ · Apr 28, 2016

markn455 said:
Where are the Nosecone Terminals located?

If you pop the nosecone off the front of the car, you will find a 12V positive terminal. search for "inverter in the frunk".

TaoJones · Apr 28, 2016

FlasherZ said:
If you pop the nosecone off the front of the car, you will find a 12V positive terminal. search for "inverter in the frunk".

Have they not moved the location of that terminal in later models?

FlasherZ · Apr 28, 2016

Perhaps. I drive one of the classics, so I only know where mine is.

In the Model X it's now underneath the cover at the back of the frunk.

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How much 12v current is available?

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