Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register
  • TMC will be going down for some maintenance soon.

Towing Alto trailer - electric question

doghousePVD

My grandfather’s car
Dec 3, 2018
587
472
New England, USA
On maiden camping trip with 2018 100X towing a Safari Condo A2124. Had some intermittent 12 V issues earlier, which a new 12 V battery seems to have resolved.

The 7 pin plug charges/connects the trailer and car batteries. On an ICE car, it trickle charges the trailer battery - generally a good thing.

Since every mile counts when pulling a trailer, the last thing I want is discharging the car for the trailer. The trailer has PV, and we usually are in a RV park and can plug in.

Is there any downside to unplugging the fuse in the trailer so the batteries can't charge each other?

Related to this, does it make sense to keep the fridge (gas/12V/120V) turned on with 12 V? One shouldn't drive with the propane on. I know electric is terribly inefficient, but it would only be while driving, and the battery is topped off each night. At night we use the shore power to run the fridge.
 

sdmack

Member
Dec 28, 2019
91
77
St George, UT
Related to this, does it make sense to keep the fridge (gas/12V/120V) turned on with 12 V? One shouldn't drive with the propane on. I know electric is terribly inefficient, but it would only be while driving, and the battery is topped off each night. At night we use the shore power to run the fridge.
Some people, out of overabundance of caution, turn off the propane while on the road, but RV propane refrigerators are designed to safely run while moving down the road. Some tunnels and ferries require you to shut the propane off at the bottle before traveling in those areas, but otherwise, leave the refrigerator in propane or auto mode. Keeps food from spoiling, the beer cold, and the ice cream firm, too.
Refrigerator in propane mode uses much less 12v power than when in 12v mode.
 
  • Like
Reactions: X-pilot

ShawnA

Supporting Member
Nov 13, 2017
924
674
Edwardsburg, MI
Hi @doghousePVD ,

The battery charge is only supposed to go one way >>> Toward the trailer while the car is "On."
That is if you use the standard "hot" pin in the 7 pin connector.

Someone on the forum had horrible problems back-feeding the car from the trailer.
The car sees voltage coming from the trailer and goes crazy - if you back-feed from the normal circuit.
There should be a diode to prevent this back-feed.
If you want the diode you will have to install it...

Check out this thread for a reference:

Power Limited - Please Schedule Service - Potentially Trailer Mode Related?

Good luck,

Shawn
 
  • Informative
Reactions: Rocky_H

doghousePVD

My grandfather’s car
Dec 3, 2018
587
472
New England, USA
I pulled the fuse in the trailer to disconnect the 12 volt connection. I never want the car to supply power to the trailer and viceversa.

I have PV on the trailer so it gets charged, and I never want the car to waste range to the trailer.
 

ngng

Member
Jul 23, 2018
645
262
Bay Area
On maiden camping trip with 2018 100X towing a Safari Condo A2124. Had some intermittent 12 V issues earlier, which a new 12 V battery seems to have resolved.

The 7 pin plug charges/connects the trailer and car batteries. On an ICE car, it trickle charges the trailer battery - generally a good thing.

Since every mile counts when pulling a trailer, the last thing I want is discharging the car for the trailer. The trailer has PV, and we usually are in a RV park and can plug in.

Is there any downside to unplugging the fuse in the trailer so the batteries can't charge each other?

Related to this, does it make sense to keep the fridge (gas/12V/120V) turned on with 12 V? One shouldn't drive with the propane on. I know electric is terribly inefficient, but it would only be while driving, and the battery is topped off each night. At night we use the shore power to run the fridge.

if your camper has solar, disconnecting the 12v seems unnecessary. your camper battery(ies) are already going to be charged, and the 12v through the trailer connector is negligible. especially compared to all the other electronics in your x.

i would also double check and verify (if equipped) your trailer's emerg breakaway battery is still being charged as this is usually supplied through the trailer harness
 

MXWing

Well-Known Member
Oct 13, 2016
7,310
17,982
USA
Notice the vehicle in the screenshot of the youtube video? :)

1620413044479.png
 

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top