Battery Isolator and Charging

Battery Isolator in the Jeep and Diode in the Trailer

 

We found out the hard way that the trailer will 'suck' the car battery dry when left connected. Even while the engine is turned off and keys removed. The connector on the 7-pin plug supplies constant 12 volts to the trailer. So the trailer battery and car battery drain each other until both are dry.
We had three such instances where the Jeep almost didn't start. Once back home, the research started. To make a long story short, we needed a way to disable the flow of electricity when the Jeep engine is not running.

Now it was time to look at the big picture and come up with a plan. The Master Plan
There are some rather expensive solutions out there, but we settled for the cheapest option, a 'solenoid'. This is a relay and the price is less than $30, But more important, it was a solution that could be installed in less than an hour.

But this is not where the story ends. The solenoid isolates the car battery when the engine is turned off, a good start to prevent most problems. It does not solve the problem where the trailer battery does not get fully charged.

We added Off Road Lights, CB Radio, Garmin GPS with Backup Camera and Dash Cam to the Jeep. We installed a Break Controller for the Electric Breaks on the Trailer. The Fridge in the Trailer runs on 110V, Propane and 12V (sort of). We added a Solar Panel and we also upgraded the Water supply system in the trailer. To make sure we don't run out of electricity, we bought a small Generator.

Electric Current and cable size
Before we dig into the individual items, here is a crash course on Electric Current. Electric Current is like water in a garden hose. Big hose supplies lots of water, small hose - not so. If you connect a small hose to the tap, you don't get lots of water at the sprinkler end, no matter if the sprinkler terminates with a big hose.
Same with cables. A small cable carries less Electric Current than a fat cable. And to confuse the topic even more, a 14 Gauge cable is thinner than a 8 Gauge cable. In a practical application, a wire from the Jeep battery to the Trailer battery is about 9 Meters. Most wires that are installed are about 14 Gauge and are original wiring. And that is our limitation.
Now it's time to explain all the individual components in more detail.
8 gauge vs 14 gauge

Solenoid
The Solenoid is just beside the Jeep Battery and connected with a 10 Gauge wire. The connection has a 15 Amp fuse and feeds the Solenoid on the right side. Two cables are connected on the left to feed the 7-pin wiring harness and the Off Road Lights.

When the ignition is off, there is NO power on the 7-pin Trailer Connector and there is NO power to the Off Road Lights. The orange cable on the front center of the Solenoid connects to a fuse inside the Jeep Fuse Box. This cable supplies power only when the ignition is on and this closes the circuit inside the Solenoid.

Electric Breaks and Break Controller
Just above the Solenoid to the right are two connectors attached to the Thermal Fuse, or Auto-Reset Fuse. This supplies power to the Break Controller and in turn to the Electric Breaks in the trailer. It is all document in the Towing a camping trailer.

Solonoid and Thermal Fuse
Trailer Battery, Diode and Inverter
To find out what cable size you need to install, enter 'cable calculator 12 Volt' in your search engine and you will get several options to find the correct type. You need to know the cable length and the required Electric Current (Amps).12 volt wireing
The cable is not a single stretch of wire, it's a patchwork that makes up the connection. In our setup, the power goes from Jeep battery to a Fuse, to the Solenoid, to the Jeep Trailer Harness. Then via 7-pin connector to the Trailer Wiring, the Diode and then splits to the Inverter and a Fuse that connects to the Trailer Battery.
We installed the MOPAR 7-pin Wire Harness that terminates with the 7-pin connector beside the hitch. See Towing a camping trailer for details and part numbers.
The Trailer wiring starts with the external wire, a bulky and sturdy cable connected to the male 7-pin connector. The wires are packed into the connector and fastened with screws on terminals. As we found out, if the plug hangs on an edge, the cables are pulled out of the plug without damage. The no-damage is the good thing, the loose wires and empty plug not so. It was dark already and Things happen when on the road, I guess. After a few minutes trying to reconnect, I postponed this undertaking to the morning.
The bulky 7-pin connector on the trailer leads to the Inverter and finally to the Trailer Battery. The bulky cable terminates just inside the trailer and continues with a wire along the inside of the trailer. This wire may be simple to replace with an 8 gauge wire, by looking at the outside size, it may be 10 or 12 gauge.

The Diode was mentioned several times so far, but never a good description or it's purpose. "A Diode is a device that allows the flow of electric current in one direction only", that's it. Electric Current now flows from the Jeep to the Trailer, but not the other way. Sounds great? But it may not be the best solution. A Diode may loose up to 0.6 volt and this in turn may cause the Trailer Battery to not get fully charged (when connected to a towing vehicle). A car battery requires about 13.5 volts to fully charge. With the Diode in in the line, only 12.9 volts reach the battery. This may cause battery damage due to permanent undercharging.
Not a major issue for us, we frequently have Hydro connection on the camp sites AND we have a Generator. During our Maritimes Trip, the lack of camp sites with electrical hook-up drained the Trailer Battery several times to below 12 volts. It is a deep cycle and it can handle the discharge. It is however frustrating when the fridge complains about Low Voltage when running on Propane. That was our reason to by a Generator. We got the Honda Generator EU1000i that provides 7.5 Amps. Plenty to charge the Trailer Battery and run the Fridge on 110 volts when parked for one or two hours during a lunch break.
"With great Power comes great Responsibility". Please obey the Generator hours posted in most camp sites.
Honda EU1000i

The Inverter is the WF-8735P Power Center from WFCO and controls the three different input sources, 110 volt, 12 volt from the Jeep and the 12 volt from the Trailer Battery. The two 12 volt sources are very likely one and the same cable. When the 110 volt is connected, the Inverter feeds power to the Trailer Battery and therefore charges the battery. To be clear, the Diode is NOT between the Inverter and Trailer Battery.

The Inverter acts like a battery charger, Bulk Charge Mode when the battery is low and Trickle Charge Mode when the battery is fully charged.
The rear of the Inverter has a lot of wires as well as the 30 Amps 100 volt utility power cable. This is a standard connector at many camp sites.<br>The front of the Inverter has two 110 volt breakers and a bunch of 12 volts fuses. The 110 volt breakers are for the camp site 30 Amps feed and the fridge. The 12 volt fuses are for the lights, fans, heater and whatever else is there. Make sure you carry some spare 12 volt fuses in the correct size. The size refers to the physical size, the car fuses are likely smaller than the inverter fuses.

Trailer Inverter WFCO 8735

Solar Panel
We got a good deal on a small Solar Panel. It generates up to 40 Watts at optimal conditions. These 40 Watts are just enough to keep the battery from draining with the Gas/Smoke Detector running and the Fridge running on Propane.
This is based on the label on the appliances and strictly mathematical. The calculation is based on 6 hours/day of average charging time.

Never really tested this theory except we know that after about 4 to 6 days of use, the battery dropped to a warning level. We did use the lights for maybe 15 minutes/day and the exhaust fan for maybe 5 minutes/day.

40 watt solar panel
We looked at Solar Panel options that really keep the trailer running but it comes with a big price tag. If our Maritimes trip is an indication, half of the camp sites were in forested areas. We had a few days on Grand Manan without any tree coverage, but most days were foggy or overcast and rain. It seems that our current Solar Panel is likely more an option to keep the battery charged when stored between trips. Our off-grid solution is the Honda Generator.
We talked about permanently mounting the panel on the roof of the trailer. Some of the new trailers as seen on RV exhibits are equipped with them. Our panel would fit nicely behind the roof fan. We still have over two months to make this decision. Like some other projects, this is in the planning phase too.
The wiring is already in place, The solar panel transformer is beside the Inverter and wired directly into the Trailer Battery. There is no Solar Panel port on our Inverter.

Off-Road Lights
The Rigid D-SS PRO Spots were installed with the Roof Rack and documented in All the Lights we need from Rigid.

Dash Cam & Power Pack
The new Dash Cam is mounted above the mirror. The first cam was a cheap version and lasted for one summer. The current cam is running since early 2018. Read the Dash Cam & Power Pack to see how we solved the problem with continuous recording and making the cam stick to the dash

Garmin and Backup Camera
The Jeep is not very user-friendly when backing up. Therefore, a Backup Camera was on the wish list for a long time.
We finally got the Garmin BC-20 Wireless Backup Camera and upgraded to the bigger Garmin Nüvi 68LM GPS at the same time. We use the Garmin GPS to record our travels. The unit stores the coordinates and they can be saved to the Computer. This file is input for many other applications like synchronizing GPS tags in images. The Sony Alpha digital camera does not record the coordinates. But with the GPS file we could update the images. This GPS file can also be imported into Google Maps to review our travel history.

CB Radio
Almost a must when going off road and no cell tower around. But the biggest benefit is when you are stuck in traffic somewhere on a highway. Big trucks in front, big trucks behind you. The truckers keep in contact with CB. It usually doesn't take long until we know exactly what is happening ahead of us.

But even a CB Radio kann leave you stranded in the Back Country. So we invested in a Satellite Tracker with two-way communication. We bought the SPOT X device, all documented in SPOTX Satellite Tracking.

Water and Grey Water
The trailer is equipped with a sink and a fresh water tank. We removed the tank, it was too big and requires more maintenance than we are willing to do. Instead of one big tank we use smaller 10 liter canister. Simple to refill, replace and keep clean.
The water spout in the sink has a manual pump. It works unless you need to clean veggies or salad. This job requires three hands, humans have two. The answer is an electric 12 volt water pump. With free flowing water also comes the need to drain and correctly dispose of the waste or gray water. It is not toxic or harmful, but may contain tooth paste, biodegradable soap and some food scraps. It still has to go to the dumping station at the camp site.
Our trailer has no gray water tank, so we purchased one that can be placed under the trailer below the pipe. The water collection problem is solved. We still have to figure out a way to carry the tank with us. As of now, the thought is to attach it to the back of the trailer with some kind of simple rack.
Both the gray water tank and the 12 volt pump are projects in the planning phase :-)

Fridge and Gas/Smoke Detector
The Gas/Smoke Detector is required by law. And with all the Propane connection in and around the trailer, it is a good thing to have. We had a few alarms after disconnecting the stove outside the trailer and storing the stove inside the trailer. The sensors are very sensitive and we are happy they work. The unit has very low power consumption.
The fridge runs on Propane and uses 12 volts to power the controller (cooling on/of, fan in the back for cooling, fridge control panel). It is very efficient on Propane and obviously on 110 volts. The fridge DOES NOT run on 12 volts while driving, it is actually disabled in the trailer. We were told that it will run on Propane while driving. We never tried this yet and always started the fridge when we stopped for a longer break.
If you choose to run the fridge on propane while driving remember that it is required by law that you stop and turn off all gas appliances before entering a gas station. This means you must do it before you even pull up to the pump.
There are dangers associated with a pressurised rubber or copper gas line while driving. Please read the operating instructions for the trailer and appliances to make your own informed decision.

Next Page: Installing the Roof Rack

First published on February 15, 2018

Timestamp: 12/05/2019 12:35:55 PM EST [on srv7cps]
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