12V Mobile Power Unit

This project was conceived as a companion 12V power source for my RV.  

When working remotely from power mains, access to 12V power is useful, such as working on a trailer, or vehicle like an RV. RV owners know that things fail often, but that is a story for another post. Sometimes a  failure can strand the RV and even create unsafe driving conditions. The worst of these are substems that are stuck deployed such as steps, slides, and awnings. 

Common  uses for a mobile 12VDC Power Unit:

• Testing trailer lights
• Power tools that are 12V compatible such as a soldering iron. Having a mobile soldering iron when working on a vehicle or trailer makes electrical work much easier. 
• USB charger: a 12V to 5V adapter for powering USB-charged devices. 

Panel view of 12V meter and discharge monitor

Battery Stowed in box

Design

Features of this mobile power unit:

• Converts a readily available tool battery technology to 12V. In my case Ryobi batteries.
• Provide for various ways of connecting to multiple types of  loads
• Use standard power connections
• Visible voltages for all electronics

12V Power Supply

Socket for the battery

This Ryobi adapter was used to connect to the battery. It comes with an integrated fuse and a main power switch.

Ryobi Battery Adapter

Battery adapters for other vendors' batteries are also available on Amazon. They are often found under a "Power Wheel" search term.

https://amzn.to/3LPfe8I

Discharge protection

If you discharge a lithium tool battery below a specified level you will damage the battery. To prevent excessive discharge a monitor is used that switches off the load at a specified level.

Discharge monitor: Voltage Disconnect Module

This module should be set up to disconnect at a value specified by the battery manufacturer. 

Ryobi batteries discharge level should be set at 14V

14V- 12v converter

Voltage converter

Tool batteries typically output more than 12V. Ryobi batteries output 14-21VDC so a down converter to 12V is necessary.

As the battery discharges the voltage will drop. A converter that will operate across the range of the battery's output voltage is needed. In the Ryobi case, this is 14-21V. 

A suitable current capacity should be chosen. This one can handle 10A. I would have preferred 20 amps because many 12V loads are that heavy. I could not find a converter that supported a 20 amp load across this wide of an input voltage range.

This converter advertised; built-in over-temperature, over-current, over-voltage, and output short-circuit protection. I have not yet tested those features.

Fuses

My implementation uses the fuse supplied with the adapter. Additional protection at the output could be added. A fuse could be provided as an adapter. 

Fabrication

Ammo Box

Ammo box

The supply is housed in a translucent plastic ammo box. You can get these on Amazon and at Walmart.

.

Holes for mounting screws, voltmeter window, and output jacks are cut into the wall of the box  

Frame

I wanted the entire assy to be removable as a single piece. To that end, a 1/4" acrylic plate was used to mount all the parts. The plate was tapped for screws as needed for mounting the parts. Screws on the outside of the box mount the frame to the inside wall. Mounted to the frame are:

• Battery Adapter: Ryobi Battery Adapter
• Voltmeter: https://amzn.to/3LRPCrT
• Discharge Protection Module: Voltage Disconnect Module
• Bannana Jacks: https://amzn.to/3ZMt1D1
• SAE socket: https://amzn.to/46DEYNj

Shown is a converter module (upper middle of the frame)  that I am not using

Battery Adapter 

The adapter was spaced from the frame by a 1/4" acrylic subplate [see photo above]. The adapter is disassembled and two mounting holes are drilled. Then 1/2 of the adapter and the spacer plate are screwed to the frame after which the adapter is reassembled in place.

Converter

The 12V converter is mounted on the side wall opposite the frame.

Adapters

A series of adapters were fabricated to facilitate connecting the power unit to various loads. 

Example configurations:

• A load can be connected directly or through an amp meter.
• A DC motor can be connected through a reversing switch so it can be operated forward and reverse.

The adapters were fabricated using SAE cable jumpers so as to keep connections standard.

WARNING: When SAE connectors are connected end to end without an adapter the polarities are reversed. This can damage the load!

To prevent this occurrence use reversing plugs where necessary.  To determine if the polarity is correct, before connecting a load connect the Polarity Tester where the load would be connected. If the LED in the polarity tester lights the connection if correct if not add a polarity reverser plug.

Adapters for connecting to: 

• Batteries: https://amzn.to/48FeBsh
• Kwikee RV step motor: https://amzn.to/3LS9s6e
• RV's awing motor: alligator clips
• Loads that use a cigarette light plug: https://amzn.to/3Q7bMZy
• Inline amp meter: https://amzn.to/3RUX1ua I used an old meter from my parts bin.
• Reversing plugs: https://amzn.to/3F7k0L8
• Polarity tester: built using LED [https://amzn.to/3ZO5HVd] and pill bottle
• Reversing switch: https://amzn.to/46jaj8o mounted in an acrylic frame with grommets
• Not shown in photo: 2.1mm power jack and plug
• Not shown in photo: USB charging connections. 
• https://amzn.to/3toLZ6r
• https://amzn.to/3ZZRchr

Sumo Rear Bump Stops

Improving the Rear Suspension 

I am very happy with the front Sumo Springs I installed so I decided to add rear Sumo Springs to my Jayco 26Y.

I got the versions that fit an E450 rear.

I got them from Etrailer:  https://www.etrailer.com/p-SSR-130-47.html

You can also get them from Amazon: https://amzn.to/3SwLFtN

This installation was done on a Jayco 26Y with HELLWIG helper springs. I was concerned that they might interfere with the springs but they do not.

All in all the installation took me about 2 hrs. With ratcheting wrenches, this would have probably taken only 1 hr.

What is in the box

The springs arrived in about 11/2 weeks packaged well in a box. The instructions can be found here: https://www.superspringsinternational.com/instructions/SSR-130-47.pdf

The instructions were simple enough but were incomplete in these ways:

• The instructions show two holes in the mounting bracket when in fact there are 4. I used the rear hole inboard of the mounting bolt.
• The ETrailer video I watched showed a left and right version. These were not marked as such and were identical.
• I was not sure whether to use the spacer or not. There are no instructions on how to tell or why to use them.

Tools

I highly advise investing in a set of ratcheting metric box wrenches. I did it with one 9/16 ratcheting box wrench (works for 14mm) and one 15mm box wrench as I have no metric ratcheting box wrenches.

The spring mounting screw is to be torqued to 20ft-lbs but I did not have a torque wrench small enough to fit in the available space so I just guessed.

I did not use the spacers and associated bolts.

Tools, removed and unused parts

Fasteners

• 15mm for the stock bump stops
• 14mm for the Sumo mounting

Preparation

One video suggested using the hydraulic lifts to jack the RV up. I decided it would be easier to use a floor jack positioned under the hydraulic jacks. Jack stands were placed as a safety measure but the RV has plenty of clearance if it were to release from the jack and I was underneath. I jacked the frame up until it took the weight off the tires. This left about a 6 1/2" clearance between the frame and the axle.

Use the Spacer or Not

Since there were no instructions on when and why to use a spacer I decided to measure the gap between the frame and the axle before lifting the RV. From this measurement, I could get an idea of how much additional pressure the spacer would create. The resting position leaves the frame about 6 1/2" above the axle. The total height of the Sumo spring was approximately 7". I decided to leave the spacers out since there would be about 1" of compression. I guessed I would not need 2" of compression. I am guessing that adding them would make an even stiffer ride. I am not trying to stiffen up the ride but reduce the rear sway. Only testing will tell if this is the right decision. If I had to add the spacers it would only require jacking up the RV and removing/replacing two bolts.

The spacer would add about 1" of additional compression.

Passenger Side Install

Remove the stock bump stop

The 15mm nut for the stock bump stop is on top of the arced section of the frame. The exhaust pipe leaves just enough room to get a box wrench onto the nut. This is where a ratcheting box wrench would speed up the installation.

15mm box wrench at 1/2 rotation per turn takes a while to remove

A smaller rachet helps but a 15mm deep socket is needed

Used this after the box wrench loosened the nut enough to get a standard socket on it.

Adding the Sumo bracket

After removing the stock stop, insert the Sumo brackets bolt up through the stock bumps hole and add the nut and washer on the top of the frame. 

Add the Sumo Spring

Insert the spring mounting bolt into the correct hole. The rear hole inboard of the frame. Then lift the spring up and mate it to the bracket. It is a little challenging to get the bolt aligned with the threaded hole in the spring and get it started. The curvature of the bracket is the same size as the perimeter of the spring when aligned. Move the spring until it is aligned with the bracket and the bolt should screw into the spring. 

Overhead view of the bracket mounting nut and spring holding bolt

Tighten the 14mm bolt on top of the spring bracket

Completing the Passenger Side Installation

Check that the bracket mounting bolt is tight.

Then torque the spring mounting bolt to 20 ft-lbs. I did not have a torque wrench that would fit into that space so I guessed. 2 grunts is about 20 lbs :). One set of instructions suggested the use of a crows foot and a small torque wrench.

Position before the jack is released.

Fully Loaded Position

Driver Side Installation

The driver-side installation uses the same steps but has easier access because there is no muffler pipe in the way. You do have to contend with a brake line bracket that is positioned under the bump stop mounting bolt. Jack up the frame and start the driver-side install.

Removing the stock bump stop with a 15 mm box wrench

Final turns with a 15 mm socket. Note the brake line bracket. 

Installing the Sumo bracket with the brake line bracket in place using a 9/16 ratchet. Don't forget the washer! 

Aligning and fastening (20 ft-lbs) the Sumo spring with the short 14mm bolt

Completed installation prior to letting down the jack

Fully loaded spring

Final Checks

• Ensure that on the passenger and driver sides, the 14 mm bracket and Sumo spring nuts and bolts are tight
• Ensure that the installation does not hamper or pinch on any wires, cable, or tubing under the RV.

While under the RV I always look for ways to better secure tubing and cables with tie-wraps.

In Conclusion

The installation was simple and easy to complete. Ratcheting box wrenches (14 & 15 mm) would have made the job a lot easier but standard tools did work. The instructions were missing some useful information regarding the mounting holes and spacer use. I will follow up this post with a report on how well the RV rides with this upgrade after the next few trips.

Enjoy and comment,

Don

RV Trim Lights

 Let There Be (more) Light

I wanted to add some trim lights on our RV to help illuminate the campsite. The RV had only one small light above the door. So I went searching for LED strings and controllers.

RV upgrades are never as simple (or as cheap) as you initially plan this was no exception.

I got this set of lights and a controller. I figured I would mount the strip on the trim and wire them to the outdoor light switch. Easy peasy!

https://kit.co/donkjr/rv-upgrade-maint-repair/led-strip

After getting the set I realized that the controller uses an IR remote. This meant that the IR sensor needed to have a clear line of sight from the outside of the RV. That is so I can change the lighting from my camping stool.

This brought into play a whole raft of weather and vibration requirements that I did not initially intend to tackle. Mounting anything outside of an RV takes some special scrutiny. It’s challenging enough mounting the LED strip on the outside of the RV now the controller needed to be mounted there as well. Actually, this would make the fragile wiring from the controller to the strip more reliable.

I could have 3D printed a custom case but I went with the switch box approach. You can find many styles of plastic electrical boxes that can be used for projects like this. In this case, I use a switch box that has a side box area intended to accommodate expanded wiring.

I bent a form-fit acrylic cover. The controller was screwed into the box and its power plug was hacked to allow the use of a Weather Pack waterproof power connecter. The IR sensor is positioned in a notch and held in place by the cover. A blade fuse was added. The LED strip plug exits the box in a position that facilities mounting the strip on the RV frame. All the cable exits were sealed with silicone. I would call the box water resistant not waterproof.

The power for this box came from the outside lights switch inside the RV. Getting from that switch through the cabinets and out the frame was not at all fun. I had to remove/replace three rear panels in the cabinets

As I am writing this I am thinking I will add a gasket to the box's acrylic cover.

Enjoy and please comment,

Don

RV Power Cord Panel

Stowing the power cord

All RVers know the annoying process of removing the main power cord from its storage compartment. 

You pull the cord fully out of the compartment, then feed it back in and through the floor of the compartment through the slot with the hinged cover and eventually to the power box.

To stow the cord you pull it fully out through the floor and then coil it into the storage compartment. 

I researched ways to make this easier. There seemed to be two prevailing approaches:

1. Cut the cord at the opening of the compartment and add a female socket connector to the cable. This facilitates plugging and unplugging the entire roll of cable rather than feeding it in and out of the storage area. This makes it easier to plug and unplug the coil of cable but you still have to feed it through the floor???
2. Put a female outlet on the side of the RV. This facilitates taking the cord from the storage area and simply plugging it into the side of the RV. To stow, the cord unplug, roll up the cord and replace it in the storage compartment 

A Different Approach

I decided to implement # 1 because I did not want to cut a hole in the RV. However, the addition of another connection in a high current cable just did not feel like the right thing to do.

Then it occurred to me why not come up with a way for the cable to exit the compartment without going through the floor. A way where the cable is just pulled out and then recoiled for storage.

I started investigating simply putting a hold in the door for the cable to exit. The latch was in the way and I really don't like cutting into the RV's skin.

Why not open the door pull out the cable and then insert a panel in the compartment opening.

I decided this would be my approach.

The Panel

I make a template & prototype from 1/4" board so that I could get the corner radiuses correct and check the fit. The final version was to be a clear acrylic. 

• The dimensions are included in the picture in case you want to make one.
• The notch in the left side is to clear the hinge,
• The nut on the right side is for the locking bolt. The acrylic version is threaded.
• The hole in the middle is for your finger to be able to insert/remove the panel
• The notch at the bottom is for the cable

The acrylic panel fastener

The acrylic panel is locked in place. The yellow item in the upper left is an AC plug tester I leave in the socket to show proper AC power.

The Locking Hardware

The panel is locked in place by a rotating disk (washer) that interposed the back surface of the compartments frame. You turn in counterclockwise to tighten and clockwise to release.

The knob for this assembly was made by pouring hot glue into a box wrench with the bolt standing in the center.

Optional Door Latch

The wife thought the door should be secured out of the way when this panel is installed so it's not flapping freely. Two magnets were glued (Plumbers goop) on the outside of the door and fender to secure the door in the open position. I use Plumbers Goop a lot on the RV. It has strong holding power but also can be removed if necessary. We will see if this will stay attached when underway.

Final Installation

Here the panel is in place with the cord captured in the bottom notch.

Look what crawled into the compartment!!

Panel installed with the door latched open

Conclusion

To hook up:

• Open the compartment door
• Pull out the cable
• Install the cord panel
Plug in the cord

To depart:

• Unplug the cord
• Pull off the clear panel
• Coil the cord in the compartment
• Close the door
• Stow the cord panel 

Enjoy and comment, 

Don