Propane Tank Sensor on a Motorhome – For Rough Roads


Here is some information from an RV Whisper customer and his experience installing and using a Mopeka XL Propane Level Sensor on his Class C 13 gallon (53 pounds) propane tank that is permanently mounted.

Immediately after the install, we went on a trip that involved hundreds of miles of poorly maintained roads, mostly dirt or gravel.  So far, the XL sensor hasn’t budged.

He mounted the sensor with some clever techniques to make sure it didn’t move or fall off, even when driving on very rough roads. Other customers have just put the XL sensor on their motorhome propane tank and had it work out well, but I suspect they may stay on paved roads or at least reasonably well maintained dirt roads. If you take your motorhome on rough roads, then these mounting tips might be useful to you.

Below are the customer comments and several PDF files with his complete data including diagrams. This customer was concerned about the mechanics of the Mopeka XL Propane Sensor. Specifically he was concerned about:

  • would it fall off while driving on rough roads
  • would it move while driving on rough roads

Download PDF Files:

Mounting a Propane Tank Sensor on a Motorhome

How Much Does It Matter If Your Propane Tank Isn’t Level

Propane Tank Levels Advanced Diagrams

Customer Comments from the Above PDF files:

When I saw that RV Whisper integrated with a Mopeka propane tank level sensor I was interested.  My small Class C has a 13-gallon propane tank mounted horizontally in the middle of the passenger side.  The standard gauge is very low and angled down, so very hard to see without kneeling.  But I was concerned about mounting one, given the inevitable jolting and possible gravel and other debris that might knock it off.

The configuration of Mopeka’s standard sensor seemed especially problematic.

I was afraid that by, in effect, mounting a rectangle to a circle, the long overhang would act as a lever and the sensor could come off too easily.  Mopeka also makes an XL sensor designed for larger tanks.  Its configuration is more symmetrical.

When I contacted Mopeka to verify that their XL model would work on my smaller tank, they said that for either version, the “… sensors have 2 magnets that both have around 3 pounds of pull for a combined total of 6 pounds of pull. Our sensors only weigh a few ounces each so they are quite affixed to the tanks.”  Still concerned about the overhang, I elected to try the XL version.

After I received and test fitted it, I found that my fears had been justified.  Even with the much shorter overhang, it didn’t take much force to rock the XL along the circumference of the tank, causing the magnets to lose purchase and the sensor to drop.  Also, the sensor could easily rotate on a horizontal axis and then even less rocking force would be needed.  No way I would trust it driving.

I decided to use Sugru to create a molded bed that would keep the sensor from rocking or rotating.  Sugru is billed as “Mouldable Glue”, which starts out at the consistency of silly putty but dries in about 30 minutes to a hard but flexible silicon in whatever shape you left it.  Here are the steps I took:

  1. Wash and dry the tank – to give the Sugru the best chance to adhere.
  2. Level the RV – to make the sensor as level as possible.  Don’t worry about this one too much.  Front to back leveling is actually not important since the mounting with the magnets will not allow adjustment on that axis.
  3. Cover the sensor with cellophane wrap.  Since we must change the batteries, we don’t want the sensor to be glued to the tank.  Sugru does not stick to cellophane.
  4. Fit the sensor and mark the location of the long ends.  Make sure it is level and in the center front-to-back.  You can use the leveling function in the Mopeka app.  Again, 100% accuracy is not vital here.
  5. Place two lines of Sugru straddling the ends you marked. Make sure you use enough to extend below the plane of the bottom of the tank. I used 4 packets of Sugru, two on either end of the sensor. (I mixed two colors – brown & green – which ended up helping the photo contrast.)
  6. Press the sensor into the Sugru. Make sure the sensor magnets make contact with the tank and relevel. Form the Sugru around the edges.
  7. Allow to cure, then remove. After 24 hours, pull off the sensor and removed the cellophane.  The Sugru bed should look something like this:
  8. Replace the sensor.
  9. Safety net (optional but recommended).  I used some adjustable bungee cords and elastic netting to create a cradle.

Immediately after the install, we went on a trip that involved hundreds of miles of poorly maintained roads, mostly dirt or gravel.  So far, the XL sensor hasn’t budged.

*  All illustrations from the Mopeka manuals.  Photos by me.

Pet Safety and Powering your Monitor Station

When you lose shore power is when you most need your monitor system to work. For Pet safety you should use a 12 Volt USB adapter to power your RV Whisper Monitor Station. Your WiFi router should also be powered off the RV batteries. so that your monitor station remains fully operational when you lose shore power and you need the system the most.

Here are two examples of 12 Volt USB power adapters.

Many newer RVs come with USB power ports already installed in them that are connected to the 12 Volt system. If a cigarette lighter socket is what you have, then a USB cigarette lighter adapter can be a good choice also, but be aware that during travel the cigarette lighter adapters often bounce loose on bumpy roads – so be sure to plug them in securely when you stop traveling for the day.

Adding a hardwired USB 12 Volt adapter is a fairly simple task for someone that has a drill, the right size drill bit, and some 12 Volt wire crimping tools.

Be sure to use the blue USB power cable that came with your RV Whisper monitor station, and be sure to use a USB power outlet rated for 2.1 Amps or higher. The blue cable is best because it uses 22AWG (thick) copper for the power and ground wires. Most USB cables use thinner copper and can introduce a voltage drop that will cause the monitor station to reset itself over and over. The red LED inside the RVM1 monitor stations should always be solid red when powered on. If the red LED blinks or turns off even occasionally, then the voltage is too low at the monitor station and you should switch to a better USB power adapter and/or the correct USB power cable.

So for Pet Safety, be sure both your RV Whisper monitor station and your WiFi router are powered off of the RV batteries so they can always be on. Especially when you lose shore power.

Boondocking with RV Whisper

Here is a review from an RV owner that camps in areas with no cell signal, no electricity and no hookups of any kind and uses solar panels to recharge his batteries.

We recently installed the RV Whisper product in our travel trailer early May 2019.

Installed are the DC Power Meter battery sensor w/external shunt and 3 temp sensors (fridge, freezer and indoor temp) for the purpose of knowing the environmental status of our trailer and for the historical information the RV Whisper provides.

Documentation and tech support was great, making the install easy.

We use the RV Whisper and sensors to get the following information from our trailer:

  • Battery state of charge.
  • Track how fast the batteries get charged from our solar system and other charge sources.
  • Track the fridge and freezer temps to make sure our food stays at safe temperature and to know when the fridge has cooled down and is ready to be loaded before leaving on a weekend trip.

We mainly “boon dock” / off-grid camp in our trailer on weekends. Using the collected data is very useful for operating our electronics in the evening and then seeing the energy production the next day. We can remotely review the battery state of state charge when the trailer is not in use which ensures the batteries are well taken care of.

The RV Whisper unit in our trailer is always powered on and remembers the 3 WiFi access points that I initially entered in the system, when we pull up near a known WiFi connection, the trailer automatically connects and the information becomes accessible via the internet. This is not a requirement just a fantastic feature. The steps are easy to add more WiFi access points as needed.

If no cell service exists and no internet access is available while camping, it is easy to connect to the local WiFi provided by the device itself to see all the information I need.

The free downloadable app is our primary way of accessing the RV Whisper while on the road, very fast and easy to use. The vehicle passenger can login to the RV Whisper while driving down the road to make sure all is well from the truck, making sure our food does not spoil during a long hot road trip.

We can also track how much voltage is being sent from the tow vehicle to the trailer battery system and we can tell the difference between the solar system voltage and the tow vehicle voltage being sent to the trailer.

The RV Whisper is a valuable tool for us, we really appreciate having access to the daily and historical logged information and that enhances our camping experience.

We cant wait to buy the “Tank Whisper” when it becomes available.