Bye2Gas
Member
The current Model Y Owners Manual lists the signals on the trailer hitch wiring connector. Pin 4 is for low voltage power (i.e. 12v), but the manual on page 99 says this:
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Living with the 16v LV battery
- Thread starter TheTinRam
- Start date
I rented a U-Haul utility trailer. I connected it by using a 7 to 4 pin converter. The lights on the trailer worked just fine. No brakes on that trailer though.
Did you also put some kind of spare battery in the frunk? If so, what did you use?
Thanks for pointing that out! I am not very experienced with towing. I went to that page in the manual but there is not much more about this. Does this mean that the power output of the hitch outlet is limited on lithium LV batty cars? What "auxiliary power" are they referring to?
I wanted to be able to run a 2 CFM air compressor, which draws 34 Amps when under load. After wracking my brain for a solution, I came up with this. I tapped into the cigarette lighter wiring in the center console and installed an SAE flush connector in the frunk. I use the charger below to charge a 100 Amp Hour Lifepo4 battery. It can be set for 2, 4, or 8 amp charging. I only installed it today, but it seems to be working like a charm. I haven’t mounted anything yet as I wanted to test it first. The charger does get hot, but the bms on the battery says it is receiving just a hair over 8 amps.
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I have no idea what 12v would be used for in a trailer. Perhaps a tiny camp trailer with a small battery so it can charge when driving? Or some sort of aux circuit fir something that needs powered all the time like a power trailer gate? But the wiring is pretty small guage so couldn’t pull too much. Guess it would be smart to not hit something with 16v that wasn’t expecting it. Probably not used very frequently.
But it doesn’t have anything to do with brakes.
typical plug pin outs attached.
But it doesn’t have anything to do with brakes.
typical plug pin outs attached.
Attachments
Mostly no sir.
The 12V aux pin on a 7 pin purpose is to charge the aux battery. The aux battery's primary purpose is for trailer breakaway. Basically a small switch is connected similarly to breakaway chains. When pulled it uses aux battery power to apply trailer brakes. While I've never seen it enforced, I believe it's a ticketable violation to run w/o said battery when trailer brakes are required.
This circuit is also commonly used for inside lighting for enclosed trailers as well as rear and side floodlight for loading/unloading. So long as the aux battery is there it can be used for larger 12v loads too. One has to watch out for over-draw on the charging circuit though...
Hope this helps clarify the intent of the 12V aux pin.
Interesting. Thanks. My trailers with brakes and an electronic brake controller never had a on board battery.
Yes, I figured it was mostly inside lights for horse trailers and the like.
But I can see that sending out 16v would wreck havoc on a 12v lead acid battery. Really need to build in a 12v regulator.
Happy to help. Yes, it would not be good to pin the 12v out if using the battery. Likekly wouldn't hurt brake servos. Mind you the stepdown transformer I showed would work just fine. Or thought I showed. Maybe in a different thread.
Here is a step down transformer that should work very well:
Here is a step down transformer that should work very well:
The problem with these converters (not technically a transformer) is that they consume power when unused.
tm3lrawd
Member
I have a 1Up USA bike rack with LED lighting. The lights work when attached to my 2023 MY. One strange feature. When I park the car, the LED lights blink about every 10 seconds for a little while after I lock the MY. This blinking eventually stops.
TomB985
Member
Fully functional, and all of this is in the manual. One of the circuits on a typical 7-pin connector is a constantly-powered 12v circuit to charge a trailer battery. This pin is not powered in cars with the Li-Ion LV battery, but the other 6 work as usual. I tow trailers frequently with mine, and the lights work just fine.
A well made point. However, unless you wire direct to battery unlikely to be an issue. When the car sleeps it power off it's accessory ports. I'm going to power my trailer adapter off of the rear power adapter port, so... In fact, at the moment I intend to simply connect the step down to a 12v power plug and plug in when needed.
I actually ordered this one:
This as I have other plans...
If it matters I see it's no load current demand is .01A, so .12W/hour @ 12v, .18W @ 16v. Even if it ran around the clock I can afford the 4 watts per day. I think the bigger questions is "does it actually work", "is stable", "is it reliable", and etc. These, and more, I don't know.
I think an improved question might be:
At what voltage are the trailer lights being driven on a LION LV EV?
My take has been they are seeing 16V. Will that have an affect on some trailer lights? dunno.
OP:
My BonAire twin cylinder from Costco work just fine on a '23YLR w/LION LV. I brough a small portable up to 100 psi so it appears to both fire up and run. Voltage drop being what it is I expected most air pumps to work. Long cords (usually) and all. It's a TC12C, and looking around my no longer be for sale. Shame, it's pretty fast.
My BonAire twin cylinder from Costco work just fine on a '23YLR w/LION LV. I brough a small portable up to 100 psi so it appears to both fire up and run. Voltage drop being what it is I expected most air pumps to work. Long cords (usually) and all. It's a TC12C, and looking around my no longer be for sale. Shame, it's pretty fast.
Since its purpose is to open the frunk when it is locked due to a dead low-voltage battery, you must obviously not put the emergency battery in the frunk.
The connectors for emergency power are under the lid in the front bumper. That's where I put the battery.
It is a small 12 V battery, a bit bigger than AA size. Found it on Amazon. I don't know the type any more.
JayPaul
Member
I just upgraded my 6x12 Aluminum trailer to have trailer brakes and added a breakaway system. My trailer weights about 760 lbs, and my motorcycle weighs about 800 lbs (or slightly more) so following Tesla's recommendations I am right at the "should have trailer brakes" weight. Plus, if I ever want to fully load my trailer (total weight 2990 lbs) I will be over.
In NY, brakeaway controllers are only required for commercial vehicles/trailers, but since I was adding brakes, it wasn't much of an additional charge to add the system. But, if you have a brakeaway system, it has to work, and be able to hold the trailer for 10 minutes (I think).
My 7 pin 12V is used to charge the 12v battery in the trailer's brakeaway system. I have a '21, so no 16V system... The battery would not recharge without the functional 12V wire in the 7 pin plug.
joeinNFLA
Member
Which brand? My Uniden R8 reads 15.7v manual says in range and it works perfect.
One quoted has been Escort Redline 360c.
16v is above 15.7v, which is above the typical car 14.5v. Who knows how much guard band it actually has in the design. Glad yours is working.
TomB985
Member
I’ve never seen 16v out of my outlets. My cooler reads 15.2v resting from the rear plug and 14.5 when running, which draws 45w.
