Solar System Upgrade - Update

My solar system for the Roadtrek has changed. I first installed a solar charger and portable panel in 2014. This was for the AGM lead acid batteries. 

200W Panel on Roof
Wiring incomplete

Then a second panel was added so I could charge both the coach and chassis batteries.  I later replaced the AGM batteries with LiFePO4.  The chronology is included in this post.

Why Solar and LiFePO4 battery combination?

I think this is the ideal approach to keeping the coach battery charged and in best condition.  Lithium batteries include a Battery Management System (BMS) which is electronics that monitors and controls the charging and the balancing of the cells.   The BMS protects from overcharging the batteries and prevents charging in temperatures below 32F.  

A battery has several cells, each of which when fully charged provide 3.65V of output.  Four cells combined in the battery provide 14.6V at full charge, or a nominal 12.8 VDC. Each of these cells will charge at slightly different rates, and one of the duties of the BMS is to control this so that eventually all of the cells will be fully and equally charged, or "balanced".  

Solar provides the energy to accomplish this, unattended.  An alternate approach is to use a 120VAC charger, but that requires a power cord and access to a power outlet.  My system does accommodate AC charging or charging via the alternator.

My Circumstances

My goals have changed since 2014. I have a 3-way refrigerator which can use propane but the controls are 12VDC. Some battery power is necessary for it, as well as lighting, etc. 

Running the refrigerator on 12VDC and conserving propane is a primary goal.  A secondary objective is running battery heaters on 12VDC when the vehicle is disconnected from shore power and in cold weather.

If 12VDC is selected for the refrigerator, the specifications indicate that 175watts or more are required, intermittently.  That's 13.7A at 12.8VDC.  I prefer to use 12VDC while in motion so that I can conserve propane.  Of course I could connect the alternator to the coach, but the solar panel provides DC during stationary periods. 

Before heading out on a trek we turn on the refrigerator and pre-chill it.  I can use 120VAC, but 12VDC is easier.  The solar supports this.

I have no intention of living off the grid, but I might be off of it for a day or two.  I had done some research and it requires about 300W to keep the Roadtrek battery charged when plugged into AC.  Part of this is losses in the Tripplite charger. However, I did add a NOCO 10A charger with LiFePO4 mode.  This more closely matched the battery manufacturer charge specifications.  I can use either the NOCO or the Tripplite.

The battery manufacturer recommends charging at up to 20A. I'd prefer to charge entirely off of solar power at any time the Roadtrek is stationary and unused.

Procedure

This is an entirely "home built" and designed system. I've been using a 100Ah battery, but using newer, smaller LiFePO4 batteries I could install two 100Ah  batteries in the original space.   Real estate in a Class B is precious and I prefer not to use it for batteries. 

My earlier posts delve into the pros and cons of LiFePO4 batteries and compare specifications to lead-acid AGM batteries.  I won't repeat that in this post.

Solar panel output and life decrease under higher temperature conditions.  For that reason, mounting of the solar panel is important.  My 210P has a fiberglass roof and it was tempting to "glue" the panel directly to the roof, as some do.  However, that may increase the panel temperature.  It is better to mount the panel slightly above the roof, but that may increase wind resistance. 

I decided upon a semi-flexible 200W panel, which was the largest that the Roadtrek roof could accommodate. I did not want to drill holes in the fiberglass roof, and that would have necessitated adding reinforcement.  I instead mounted T-track to the roof using 3M VHB tape. The solar panel was mounted atop this.  I also installed polycarbonate plastic panels under the solar panel. This provides a "sandwich" which slightly elevates the panel above the roof, supports the panel and promotes airflow beneath the panel.  The wind resistance is slight.

I routed the solar wiring through the heat pump area, at the rear of the Roadtrek and avoided drilling holes for this in the roof. 

I want to avoid roof leaks too.  I want the operation to be as maintenance free as possible. The Roadtrek 210P has had no leaks and I want that to continue.

The system installed accommodates using the rooftop panel or a portable panel. I installed a jack for a portable panel in one of the rear exterior bays. I can use a portable panel or I can plug-in 12VDC devices and charge them or use them. 

I chose a better quality battery that does not include internal heaters.  LiFePO4 batteries cannot be charged at below 32F.  So, they must be heated in cold weather.  I decided upon using external 120VAC and 12VDC heaters, independently controlled with thermostats.  When it is cold and the coach is on AC power I use 120VAC to heat the battery.  At other times I use 12VDC. When in movement I can supplement the solar and use the alternator to heat the battery.  

The heaters were installed in 2022 and have worked well. 

The battery BMS assures that the battery does not overcharge of over discharge.  I also installed a "Battery Protection" device.  This monitors the battery voltage and automatically disconnects the battery if the voltage decreases to a preset low limit.  The purpose is to disconnect the battery while there remains some useful energy. I can remotely reconnect and provide power if necessary.  It is controlled using my Android phone. 

The solar system charge settings are matched to the battery manufacturers requirements.

The installed system can provide 20A for 5 hours when off of solar (overnight) or about 8A for 12 hours.  On solar it can provide 10 to 15A continuously without draining the battery. This is determined by the solar energy available. The battery can function down to 10.4V, which is the voltage at which the BMS will disconnect the battery. 

Why only one 100Ah battery?

The Lithium battery I installed can be discharged down to 10.4 volts.  However, it better to avoid this so discharging to 11.2 to 11.8 volts is preferred to achieve the design life of the battery.  That's in the range of 5-10% SOC or State of Charge. 

For comparison, an AGM battery shouldn't be discharged below 50% SOC to achieve rated life.

This implies that a 200Ah AGM battery can routinely provide 100Ah of capacity, but more at the sacrifice of battery life. A single 100Ah LiFePO4 battery can provide 90-95Ah with little degradation. So, a single 100Ah lithium battery can nearly replace a 200Ah AGM battery. 

What I could gain using two 100Ah of lithium is about 180-190Ah of useable capacity, which exceeds that of 200Ah AGM batteries. 

In 2022 I surmised that one would work.  I also concluded that improvements in manufacturing and battery technology would allow me to add a second battery, or replace both for less than $400 at some time in the future.  That is where we are, today.

For more on my transition to Lithium see the links to solar on the right.  Here is one such link: 

https://roadtrek210.blogspot.com/2022/04/transitioning-to-lifepo-batteries.html

Chronology

2014:  That first panel was a portable 30W solar panel to keep the engine battery charged. I stored the Roadtrek outdoors and there was no AC outlet available.  Then I added a de-sulfating solar controller with portable 50W solar panel for the coach AGM batteries. My goal was simple:  keep the batteries charged when stored outdoors.

2022:  I made a major change in April & May 2022.  I installed a better solar charging system for a larger 200W solar panel, replaced the AGM batteries with LiFePO4, and added both 120VAC and 12VDC heaters for the battery.  Lithium batteries can't be charged at below 32F, so some type of heat is necessary for winter use; my coach battery is located outside the coach interior and is exposed to freezing weather.  I continued to use portable solar panels. 

I also installed a device to protect the battery from low voltage discharge.   I used a setting of 11.80V as an automated cutoff.  This is adjustable and lithium can tolerate deep discharges better than AGM batteries. 

2025: I installed a 200W solar panel on the roof.  Circumstances delayed this, and I decided to delay further until we completed our 2025 mult-month, 7,200 mile trek. 

I created several blog posts about this. 

My goals have changed. I have a 3-way refrigerator which can use propane but the controls are 12VDC. Some battery power is necessary for it, as well as lighting, etc. If 12VDC is selected for the refrigerator, the specifications indicate that 175watts or more are required.  That's  13.5A at 13VDC.  If I use 12VDC while travelling I can conserve propane.  Of course I could connect the alternator to the coach, but the solar panel provides DC during stationary periods. 

Before heading out on a trek we turn on the refrigerator.  I can use 120VAC, but 12VDC is easier.  The solar supports this.

I have no intention of living off the grid, but I might be off of it for a day or two.  I had done some research and it requires about 300W to keep the Roadtrek battery charged when plugged into AC.  Part of this is losses in the Tripplite charger. However, I did switch to a NOCO 10A charger with LiFePO4 mode.  I'd prefer to charge entirely off of solar power at any time the Roadtrek is stationary and unused.

In 2022 I added a Renogy solar charge controller. At the time I was using it with a portable solar panel.  This was an entirely "home built" system of my design.  

When I installed, I intended to put a solar panel on the roof in the future.  It took a while to find the appropriate panel.  Dimensions were the problem. I found a suitable 200W semi-rigid panel.  I also purchased materials to fasten it to the roof, but I wanted it to "stand off".  One issue with solar panels is heat.  This can reduce power output and the life of the panel. On the other hand, I also want to minimize wind resistance.  

I chose metal T-track to fasten to the Roadtrek roof.  The roof of the 210P is fiberglass, and I didn't want to puncture it, or glue the panel directly to it.  Instead, I purchased polycarbonate greenhouse panels, aluminum T-Track, 3M VHB tape and bolts.

The track is attached to the roof using the VHB tape. A polycarbonate panel can be set between the tracks to provide airflow and support the panel if one should lean on it.  The panel is attached at eight points to the track using bolts, nuts, washers and lock washers.

Alternately, the polycarbonate can be installed above the T-Track. This raises the panel about 1/4 inch and aids airflow. 

Circumstances delayed the project.  The earliest I could have done this in Spring 2025, but decided to do it in the fall.  So, here we are!

Solar Panel wiring will be routed through the air conditioner enclosure into the interior of the Roadtrek. I'll add a slot to the cover of the AC, but there will be no penetrations of the roof.   

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Note: No AI tools were used to produce this blog. Most photos are unretouched.

(c) 2025 N. Retzke 

Solar and Potential Savings in a Class B RV

 

Financial benefits of solar on a 210P

Is there a financial incentive? At the AZ resort, electricity is $13.00 basic service charge monthly + $0.07612 for the first 500kWh, then $0.09337 for each kWh in the range 501-1000. To this are added Arizona assessments, environmental compliance charges, a utility ‘power supply’ charge, a PPFAC charge and taxes.  Typical energy charges adding all of these is about $0.1495 per kWh.

I’ve monitored the AC power used to simply power the coach, keep the AGM batteries charged and a vent fan running. The cost for that amount of electricity is about $51.67 each month.  Using solar and a good battery may reduce my 120VAC power bill by about $310 each season in AZ. If the batteries run well for 7 years, that’s a possible $2,170 in electric bills I won’t pay. 

The other six months of the year, at our “lily pad” in MI the cost per kWh is currently $0.14. That’s a cost of $290.30 to charge batteries, power the 12VDC coach, etc. for six months.  

Add the possible AZ and MI savings, and I may save $600.30 each year, or $4,202 over the projected life span of the coach battery. 

These are approximate numbers taken with intermittent readings prior to replacing the AGM batteries with LiFePO4.

Of course, to this add any 120VAC consumed.  I don't have a "full-solar" installation. At present the Tripp-lite charger/inverter is "Off" and I use AC for the Cool-Cat air conditioner/heat pump, the refrigerator 120V heater and microwave/convection oven. 

If more solar were available, I could probably run the refrigerator off 12VDC during daylight hours, increasing the savings from solar. However, "full solar" existence isn't practical in my opinion.  The Cool-Cat heat pump requires 1,227 watts when the compressor is running and cooling.  To that add electricity for the refrigerator, etc. as well as battery charging current to be stored for overnight use.  I'd need a lot of batteries and a lot of solar panels.  The roof of the 210P has space for at most 200W of panels.  I can add portable panels to the capacity of the controller and more batteries but living off the grid is not my goal.

Why? I won't park a Roadtrek in full sun in Arizona when the ambient reaches 100F in the shade. That's a recipe for a human BBQ.  

This season a couple moved into the resort after a trial at boondocking in nearby Quartzite.  Their several months-long experiment occurred with peak temperatures only about 80F.  They related their experienced and told us that they made the decision to get a site in the resort. They decided the resort fees were worth it as this provided unlimited running water, sufficient power for air conditioning, easy tank dump, etc.  Oh, and a bar & grill, swimming pools and internet access, too. 

Measuring AC Power consumed

I have two methods. One is the Power Protection Device at the 30A connector.  It includes an ammeter display. It is useful for roughly monitoring the amperes being consumed @ 120VAC.

AC Amperes with Cool-Cat AC running, Tripp-lite charging, refrigerator on AC

The other device I use is a Kill-a-Watt meter.  This can be used to determine the amperes and watts consumed on 120VAC circuits, or for individual appliances.  It is accurate and precise. It allows a variety of measurements and price calculations at any entered cost per kW. It will calculate the power consumed at any entered price per KWh and it will totalize this cost.  Here's an example of an instantaneous ammeter reading:

Kill-a-Watt indicates Coach 120VAC at 10.23A. Measurement 
with Cool-Cat air conditioner running, Tripp-lite not charging and
minimal appliances powered up

Measuring the Solar Power Available

The MPPT controller has calculations and historical data available. Data is accumulated and stored monthly. Some of the statistics available:

• Power generated
• Charge Ah same day
• Max charge power
• Max battery volt
• Running days total
• Battery full charge times
• Battery charge Ah total
• Generation amount kWh

Initial Observation

How is the LiFePO4 battery and charger doing?  So far, very well. I keep the coach powered up on solar with the vent fan running. The Tripp-Lite charger/inverter not being used. This is an experiment.  Every day the coach battery is fully recharged after a few hours in the morning sun.  Of course, this is AZ with a lot of sun.  On the other hand, this is a small 50W solar panel which is showing its age. Power output has decreased and peaks at about 85% of rated. 

It is premature to call this a success, or the LiFePO4 battery superior to the AGM batteries. For one thing, this trial has been a little over a month in duration and we are stationary. For another, I did install the coach battery in the outside compartment. It is a well-known fact that the battery management system (BMS) of a LiFePO4 battery will not allow it to be charged if the battery temperature falls below 32F. G and I have trekked and camped overnight in temperatures as low as 5F. As a consequence I did install low-wattage 12VDC and 120VAC compartment heaters.  We’ll see how that works. 

There are some LiFePO4 batteries which incorporate 12VDC heaters in the battery.  I could have chosen this type.  However, I am concerned about how much energy those heaters may use when off the grid or while the Roadtrek is stored in cold weather and not plugged into shore power. I decided two 12VDC and a 120VAC heater and solar power were a better solution, in my circumstances.  I also installed an automatic low-voltage disconnect for the battery.  The BMS will disconnect and prevent the battery from completely discharging, but LiFePO4 batteries are best disconnected at a higher voltage threshold if maximum cycles and life are to be achieved. Ergo the automatic disconnect. 

Increasing the solar Available

My plans will increase the amount of solar for the Roadtrek.  There are limitations because of the available roof space.  I have no such limitations in AZ under the shelter, so I can add even more kW on my shelter roof. 

Background Information

It was time to replace the coach batteries in my 2013 210P.  I attended the FMCA Convention in Tucson in March, and I used that opportunity to visit with battery suppliers and manufacturers in the exhibit hall. There was a battery seminar scheduled, but an issue prevented the presenter from being there so that seminar was cancelled.

I had to choose:  AGMs or LiFePO4. To assist in making that choice I wanted to review the latest technology and I didn’t want to overspend on Lithium-ion if I went that route.

My Roadtrek is relatively new, but the first set of AGM batteries were ruined when the Roadtrek control panel “Inverter OFF-ON” switch failed to open when I put it in the “OFF” position.  Sitting in storage in that condition for a couple of weeks completely depleted the AGM batteries, ruining them. After that experience I turned off the inverter function when I store the Roadtrek.  I did this by changing the Tripp-lite mode switch to “Charge Only”.

When the first set of AGM batteries failed I replaced them with similar batteries and installed a 50W solar panel and 180W desulfating solar controller to keep them charged.

LiFePO4 Today

LiFePO4 technology continues to evolve. I’m currently aware of two different cell construction techniques. I investigated different constructions and manufacturers.

Prices for a 100Ah battery range from about $350 to $950 each, plus shipping and tax.  Why is that?  There are differing cell qualities.  There may also be large mark-ups by some sellers.  I determined that there is no standard for determining cell quality in China, where many or most of the “internals” in these batteries are manufactured.  As a consequence, it is important to purchase from a reputable manufacturer. It is possible to overpay, if one assumes the higher the price the better the quality.  On the other hand, there is a lower price threshold below which it would be better to avoid.

A Decision in favor of LiFePO4

I continued my research and decided upon a  LiFePO4 battery from a quality manufacturer.  Delivered and with state sales tax the price was   $624.93.  It arrived on April 1, 2022.

I'll run some of the solar numbers later in this post. However, I concluded the LiFePO4 would be more reliable and therefore more likely to achieve the solar performance I wanted.  Solar panels are only a  portion of the system.  Energy storage is also very important.

The was shipped 30% charged, which is normal for this manufacturer.  I promptly charged it using a 10A charger which was compatible with the specifications for this Lithium-ion battery.

A new MPPT solar controller

I had determined that my solar controller with a de-sulfating mode was not ideal for the Lithium-Ion battery. It was ideal for AGM batteries.  I replaced the solar controller with an MPPT type; it had a user mode with custom settings which were ideal per the battery manufacturer’s specification.  I installed that, entered the proper settings and have since allowed it to charge the coach battery and run basic appliances off the grid (lights, fan, etc.).  I’m satisfied with the initial performance.

I’m currently in southwest Arizona with the Roadtrek on my winter site. It is parked under a shelter, which is why I used a portable solar panel. The panel is currently on the shelter roof. The ambient may be 60F at night but can reach 90F during the day. We do get some morning sun loading in the front of the Roadtrek. I run the vent fan most of the day unless I am using the Cool-Cat heat pump/AC.

(c) N. Retzke 2022

Solar Installation

 

Solar Panels don't work when the Roadtrek is under cover.

Solar system upgrade

Shortly after I purchased the Roadtrek I installed a portable solar panel and controller.  I decided to use a portable panel because when camping in the summer I prefer a shady location.  Solar panels don't work well in full shade, but the Roadtrek is far more comfortable when parked that way. 

I installed the panel to keep the coach batteries charged when off the grid and in particular when storing the Roadtrek.  Our boondocking experiences are short, so I don't need a lot of solar energy, preferring the Onan generator to run the AC appliances and Cool Cat heat pump.

Our winter "lily pad" is in Arizona and it can get quite warm, even in winter.  Particularly if we are parked in full sun.  When at the site in the photo above, the solar panel is on the roof overhead and so it is providing electricity most of the day, while the Roadtrek is in the shade.

When we are camping and park in the shade, the interior of the Roadtrek is generally whatever the ambient temperature is.  If it is 78F, then the interior is 78F because we ventilate it. Of course, when trekking full shade is not always available.  So, we are sometimes in partial shade and at other times in full sun.  The benefits of rooftop solar is reduced because of the shade. Ergo the portable solar panel.

An opportunity for change

In recent years the quality of flexible Monocrystalline solar panels, their price and warranties have improved. We also have the benefit of the experiences of early adaptors who have experimented with a variety of mounting approaches and panels.

When I decided to replace the AGM coach batteries with Lithium-ion LiFePO4, I also had the opportunity for other improvements which included expanding the solar systems.

Of course, one of the challenges of a Class B is living with the space limitations of the interior and exterior compartments.  I wasn't willing to use a lot of interior real estate to house batteries, the solar controller, wiring and etc. 

Ultimately, I decided to mount the LiFePO4 battery in the outside compartment, install 12VDC and 120VAC heaters to warm the battery when the compartment temperature falls below 40F.  I mounted the components and routed the wiring via a variety of nooks and crannies. 

I've posted recently about the selection process and heaters, so I won't repeat that here.  This post will focus on some of the other installation details.

Currently, the Roadtrek is under a shelter with limited space above. Furthermore, it was 96F yesterday, and today it is a balmy 91F in the shade.  In this weather I won't be mounting the rooftop solar until we get to our lily pad in Michigan.

Instead, I concentrated on installing everything to support the portable solar panel, with some preparation for the rooftop solar.

Solar wiring and controller

Solar MPPT Controller, battery voltage 13.3V

I reviewed the available locations, the paths for the wiring of the heaters, the availability of 120VAC and so on.  I decided to install the MPPT solar charge controller on available wall space adjacent to the TV in the rear of the coach. I installed a bulkhead fitting beneath the controller for plugging-in the portable solar panel. A second connector will be installed for the rooftop panel. There is also a 65A connector for the controller 12VDC output.  I want to easily disconnect the controller if necessary for maintenance purposes.

Bulkhead connector for solar panel wiring

A matching connector was installed in the exterior compartment. This is where I plug-in the portable solar panel. I included a MC4 adapter. What remained to do was to route the solar cables to connect these bulkheads. I did come up with an approach to simultaneously use both rooftop and portable panels, if that is desired to collect more solar energy.

Connector for portable solar panel

The solar cable was routed from the exterior compartment, into the coach electrical compartment at the rear of the Roadtrek, and from there into the compartment adjacent to the interior fresh water tank. It was terminated on a fuse and terminal block and from there it was routed behind the fabric panel to the armoire and to the interior electrical bulkhead.   I wanted to install a fuse and terminal blocks to provide access for future maintenance. 

Solar cable exiting exterior compartment and upward into coach electrical compartment

Portable solar panel cable in electrical compartment

I routed the solar panel wiring from the electrical compartment to the terminal blocks installed adjacent to the interior fresh water tank.  I removed the 12VDC wiring cover in the armoire. and pushed a solid 14AWG behind the fabric side panel, from the armoire to the fresh water tank compartment.  I then used that to fish very flexible 18AWG.   The 18AWG would be used to pull the solar cable through.

I soldered and taped the solar cables to the 18AWG so they could be pulled. Solder is a superior strength connection and smaller in diameter than a butt slice connector.  This approach was necessary because the wiring was a tight fit.

Solar cable prepared for pulling

To give myself sufficient space to grab the wires in the wall I temporarily removed the fresh water tank fill line and pulled the solar wire through.

  

Solar cable at fresh water tank

To do the pull I removed the wiring cover inside the armoire and disconnected the cable for the power seat, at the UP-DOWN switch. This permitted me to move that cable out of the way.

  

Power seat switch electrical connector in armoire

I then pulled the solar cable into the armoire and connected it to the bulkhead connector.

 

Solar cable into armoire.

    

Bulkhead cable connected to solar cable

   

Front of solar bulkhead connector on armoire below MPPT controller

The mid-point of the solar cables were terminated in the compartment adjacent to the interior fresh water tank. This for maintenance purposes, and I did install a fuse on the solar panel positive.

Solar terminated adjacent to interior fresh water tank

I then put the armoire interior wiring cover back in place. 

      

Interior of armoire

I terminated the12VDC power at the MPPT controller and powered it up. I then entered the necessary battery parameters.  Prior to connecting the MPPT controller to the bulkhead solar connector I plugged-in the solar panel and checked the polarity at the bulkhead connector. Satisfied it was proper I plugged in the solar cable at the controller.

Operational MPPT controller, 12VDC power and solar panel connected

     

Portable solar panel

  (c) 2022 N. Retzke

Notes:

1. This is not a how-to-do-it post.  I'm providing it as-is and it is not a recommendation or a procedure manual.
2. I'll be installing a rooftop panel when I'm at my summer lily pad location.

  

New LiFePO4 battery, new solar, battery compartment heaters

 

Work station in Arizona

The modifications are substantially complete.  Earlier posts go into the pros and cons of LiFePO4 batteries, and the issues encountered when attempting to charge them in below freezing conditions.  I decided to install small heaters in the outside battery compartment.  I also upgraded the solar system I had installed in 2014. 

I'm of the opinion that components should be sized and selected carefully so as to extract the best benefits from the system.  In other words, the components should be selected to perform as a system.  It is desireable to get the best performance for a specific cost. System component selection includes the type and wattage of solar panels, the solar controller type and capacity, the Ah of the battery, the wattage of the inverter and other components, and even the size and ampacity of the wiring.   To do otherwise means overspending on some components while being performance limited by the weakest links in the chain.

In my experience, too many of us RVers are inclined to spend our money to get what we think we might need, rather than spending it on what we will use.  Experience may be the best teacher. 

When I decided to replace the coach batteries, I concluded this was an opportune time to evaluate the performance of my existing solar-battery charging system and make any alterations. In doing so I unconcealed  the weak link in the chain and decided to so something about it. Of course, this is an iterative process; once the weakest link is eliminated, there is the next one on this particular chain to deal with. 

I suggest some self-control and restraint may be in order. Otherwise, one might build a Roadtrek with a "warp-drive" Lithium-ion battery pack.  Oops, G just reminded me that this has already been done.  LOL.

This is the list of tasks:

1. Remove AGM coach batteries, install Lithium-ion LiFePO4 battery.
2. Mount shunt on the new battery (for the existing remote volt-ammeter display).
3. Remove existing de-sulfating solar controller used with AGM batteries.
4. Install (2) 12VDC battery compartment heaters and controllers.
5. Install (1) 120VAC battery compartment heater and controller. This heater has adjustable wattage.
6. Install MPPT solar controller. I chose a controller which accepts "user" settings which precisely match the recommendations of the battery manufacturer.
7. Install Blue-tooth communications module for MPPT.
8. Install low battery voltage automatic cutoff switch. 
9. Install fuses and wiring for the above.
10. Connect existing solar panel. Convert this to a remote portable solar panel.
11. Prep for a new rooftop solar panel. (2 total panels). This is anticipated to be a 100W solar panel on roof (to do). Wattage limited by the rooftop real estate available. 
12. Retain 120VAC power in battery compartment (installed 2014).
13. Install connector for portable Li-ion battery charger in the battery compartment. This is optional, but permits charging the battery without solar or the use of the Tripp-lite charger/inverter installed by the Roadtrek factory.

Remaining, to do:

1. Complete the solar panel wiring.  Add new rooftop 100W flexible solar panel. The goal is to have one mounted on the roof and one portable.  The existing panel is wired as the portable. This will allow parking in shade while simultaneously acquiring some solar energy via the portable panel.  I expect parking in the shade will be preferred to parking in full sun when the outside temperature is above 100F.  This is based upon our experience. LOL. 

Wiring:

All wiring is properly sized for the amperes which will be carried.  Fuses were added to protect the DC wiring. I did install a fuse for the portable solar panel. 

1. Battery wiring modifications are 4AWG.
2. The main Solar Panel wiring is 10AWG. Portable solar panel wiring is 12/14 AWG.  All solar wiring is new.
3. The 12VDC MPPT output is 10AWG and fused for 20A. 
4. The 120VAC compartment heater is sourced by the Roadtrek installed GFCI outlet under the side door passenger seat.  A power strip with circuit breaker was added. The power strip has an Off-On switch. This heater is controlled by a temperature controller and an adjustable watt control was added to vary the heat.
5. The 12VDC from the battery to power the 12VDC heaters is wired with a SAE connector cable, 16AWG and fused at 10A.  After the fuse each controller and each compartment heater is wired using 18AWG. Each controller/heater combination has an Off-On switch and a fuse. Actual connected amperes per controller = 2.0A (24W), but 18AWG can accommodate a significantly higher wattage heater, up to 200W and the controllers can each manage up to 120W.  None of the components should be stressed as sized.
6. DC power connectors are rated 65A.
7. Shunt for remote volt-ammeter was connected to the new battery.
8. Tripp-lite charger-inverter was retained. 
9. A plug-in connector is wired to the battery for a portable Li-ion charger, if that is desired to charge the battery. 
10. Each controller has a temperature sensor.  These are located in the battery compartment. Two are connected with 18AWG and one uses the factory provided cable, about 1/8 inch OD (AWG unknown).
11. The MPPT solar controller is wired with connectors for quick and easy removal, if that should be required.
12. The MPPT solar controller includes a temperature sensor. This is located in the battery compartment.  This is not necessary for the functioning of the MPPT controller with LiFePO4 battery, but it is a convenient method of monitoring the compartment temperature.  The controller and battery parameters including compartment temperature are displayed on a LCD display as well as via a smart-phone blue-tooth app. 

Top view - Heater Controls installed beneath rear-side entry passenger seat.
These are accessed by flipping up the seat bottom which is on a hinge.
When not in use or not required heater power is OFF using the switches.

Under side wiring - Heater Controls Shelf

Initial Heater settings (adjustable, using battery compartment temperature). System design can accommodate higher wattage heaters if this is determined to be necessary.)

. 

Battery Installation - Heater wiring and temperature sensors exposed,
prior to being covered.

Silicone heat pad cover and 12VDC heater controls fuse

Top view - 12VDC from MPPT Solar controller-
Mounted adjacent to interior water tank - Not yet installed:
portable solar panel fuse blocks

Battery Monitor DC Voltmeter-Ammeter mounted adjacent to RT power center. Voltmeter added in 2014. This is connected to the coach battery via a shunt and the circuit is fused. Connections are before any disconnect, so the battery voltage can be read even with the Roadtrek DC disconnect in the "off" position. 
I repeat, the circuit is independently fused!
An Off-On switch turns off power to the meter when not in use.

MPPT Solar Controller smart-phone App. 
Other screens provide more detail, control of load and history

Issues, Observations & Procedures:

1. I installed the MPPT solar controller, but two days later the LCD screen went blank.  I thought it might be some sort of "screen saver" but pushing the front buttons got no response.  The Blue-tooth (r) smart phone application worked fine and indicated the controller was functioning normally.  I contacted the factory and they suggested a hard reset (disconnect solar panels and power down the controller).  After 30 minutes I powered it back up. No change.  Renogy had me take some voltmeter readings to confirm all was properly connected. I sent photos to them and even several smart-phone screens at their request.  They agreed that the controller was performing normally but the LCD screen was inexplicably blank. They concluded it was a failure and the controller was replaced at no cost to me by the supplier.  
2. Making certain wiring changes in a class B can be challenging.  It took a bit of thinking and disassembly to determine how to do this; where to mount components, route the wiring, etc.  I determined a course of action prior to purchase of the various components.  Purchasing the battery was the easy part, after I had decided upon 1) Manufacturer, 2) AH, and 3) Where to mount it.
3. I didn't want to remove the side fabric panel in the inside rear of the Roadtrek.  To do this would have required more deconstruction than I wanted to do.  As it is, I had to temporarily remove some of the freshwater plumbing to gain access.  It took a bit of effort, but I was able to fish a stiff wire behind the fabric panel and pulled the new wiring for the portable solar panel into the space between the liner and the exterior fiberglass coach shell.  A new plug-in connector for the portable panel will be installed inside the passenger side rear exterior compartment. 
4. The solar panel system will be designed to accommodate using one or two panels, one fixed and one portable. The reason to have a portable panel is this will allow adding solar when the vehicle is stationary.  It also permits parking the Roadtrek with the rooftop panel in the shade while the portable panel is placed in full sun. However, if one panel is in full sun and the other in partial/full shade, series wiring is not optimal.  The design addresses this.
5. I built and wired the battery heater controls and tested them with the heaters on a bench.  This proved the wiring and functionality.  I wanted to bench test so that if any issues occurred after installation in the Roadtrek it would be attributed to the coach wiring and more easily isolated and corrected. 
6. I used ring terminals throughout which is prudent in an installation subject to vibration and jolts.  I used heat-shrink tubing to protect, insulate and support smaller wires at the connectors. I installed the heat-shrink tubing where appropriate. 
7. The 12VDC for the heaters is wired directly from the batteries with an ATC fuse. The fuse is within a foot of the battery + connector. In this manner the 12V heater system is protected and can operate independently of the Roadtrek power disconnect. I used an automotive SAE connector dis-connect cable.  There is no acceptable way to install a terminal block and I won't use a butt-splice for power. I joined the coach battery cable to the SAE cable using ring terminals bolted and insulated with shrink-tubing. 
8. The solar controller for the AGM batteries was installed by me inside the battery compartment in 2014.  This was disconnected when I installed the LiFePO4 battery. The replacement controller is larger, and I wanted it installed inside the coach. This required a change in DC wiring.
9. I decided upon a more costly MPPT solar controller so as to extract as much out of the solar panel(s) as possible.  I don't plan on living off the grid with solar.  But I do want to have sufficient solar to keep the battery charged and sufficient 12VDC for the basics of the coach (refrigerator controls, hot water heater controls, overhead fan, propane alarm, lights, PC, phone charging, etc.  But not all at once, LOL.).  
10. I oversized most of the heater circuit electrical components. Temperature controllers are rated 10A or more, wiring for the heaters has greater ampacity than required. Cabling for longer runs is 16AWG multi-conductor with jacket. This did increase the cost, but should provide trouble-free operation. Wiring outside the coach is protected and is installed in wire-loom split tubing which is properly supported.
11. I used 65A protected connectors for the battery connection to the MPPT solar controller.  This is an independently fused circuit, but I wanted a means to easily and safely disconnect battery power at the controller.
12. Solar panels are connected with MC4 connecters. 
13. I made several simple wiring sketches of how to add the low-voltage battery disconnect and placement relative to the existing 50A circuit breaker and the inverter.  I was able to mount the disconnect adjacent to the Tripp-lite inverter/charger.  I was able to re-arrange the 12VDC+ wiring for the disconnect and was able to add 12VDC wiring from the solar controller using available space.
14. The heater wiring was designed in my head, no sketches made.  I made a mental list of what was required, compared this to my inventory in Arizona and purchased what was needed.
15. I marked various power conductors and other wiring clearly.  I'll make a drawing for posterity and future maintenance.
16. I have a bit of clean-up to do in the battery compartment, but the project is essentially complete.
17. I'll add the second solar panel when convenient.  I'd like to see how this performs before I do that.
18. When not is use all heater controls are turned off using the switches I installed for this purpose. 
19. With adequate solar, the battery separator can be in the OFF state when travelling.  

Parts and Costs:

I used off- the -shelf components.  To reduce the cost of the battery compartment heaters, I used 12VDC temperature controllers which display in degrees Celsius.  The 120VAC control does display degrees F.  This list is not necessarily all-inclusive; see Note 1 at the end of this post.

Temperature control and compartment heater components:

120VAC temperature controller: $19.00.

12VDC temperature controllers: $7.00 each. (Total $14.00)

120VAC heater: $13.00.

4-outlet AC power strip with circuit breaker: $9.00.

12VDC heaters: $9.00 each (Total $18.00).

Heat Resistant Thin Silicone Grade Rubber Gasket Sheet $9.00.

Off-On toggle switches: $2.00 each (Total $4.00).

5-pair 65A connectors: $7.50 (one used).

SAE Quick connect bulkhead fittings 2-used, $5.00 each (Total $10.00)

MC-4 to SAE portable solar panel connector, 35A, 10AWG: $15.00.

Five 4-point terminal blocks: $2.40 each  (Total $12.00).

Two ATC/ATO inline fuse holders $6.00 ($3.00 each, one shunted for 12VDC negative). 

Solar and battery related components:

Automatic Low-voltage battery disconnect: $83.00.

MPPT solar controller:  $111.00.

Li-Ion LeFePO4 battery, 100 Ah: $575.00.

6-terminal buss bar (battery negative to MPPT): $13.00.

60 ft. 10 AWG wire for solar: $40.00

Two ATC/ATO inline fuse holders $6.00 ($3.00 each). 

4 AWG cables with lugs for automatic low-voltage battery disconnect: $13.00.

Battery manual disconnect switch: $15.00.

MC-4 connectors for solar cables w/ tool.  10 pairs $16.00.

Hardware, misc. wire and terminations (some from my inventory):

2/C 18AWG, 65 ft: $13.00.

2/C 16AWG, 33 ft. $23.00.

#16-14 butt splice connectors.

#22-16 butt splice connectors.

Thermal adhesive tape, about 5 ft. used.

20 ft. 1/2" wire loom split tubing: $13.00.

M8 bolt, nut, washer.

M4 screws, nuts, washers.

8-32 pan head machine screws, nuts, washers.

Heat shrink tubing, various diameters.

Nylon screw mounting cable clips, various sizes.

Zip wire ties and adhesive mounts, various sizes.

3/14" wide double coated foam tape.

Ring type wire connectors, various sizes #18-#10AWG.

#8 x 3/4" self-drilling pan head screws.

#8 x 1-1/4" wood screws. 

1-1/2 x 1-1/2 aluminum angle.

3/4 x 3-1/2 wood slat, length as required.

3/4 x 7 wood shelving. 

Gorilla glue.

Notes:

1. This is not a how-to-do-it post.  I'm providing it as-is and it is not a recommendation or a procedure manual.
2. When not in use all heater circuits are turned off using the switches I installed for this purpose. The 12V heaters are fused and controlled independent of the Roadtrek battery disconnect switch.
3. My solar panels for test purposes are (1) 30A and (1) 50A.
4. I'll be installing a rooftop panel and have wired for a portable panel. 
5. Every trekker has goals and expectations.  It is useful to outfit the Roadtrek so that their personal goals can be realized.  This included comfort expectations, the available heat, 12VDC and 120VAC power, cooling and water. 

(c) N. Retzke 2022

Adding LiFePO4 cold weather heaters, solar, etc.

 

3- Stage battery compartment heating

The installation of the LiFePO4 battery in the exterior compartment of the Roadtrek was straightforward.  This is a progress report.

Second step was to upgrade the solar power system.  This is nearly complete.  Integrating it into the existing Roadtrek 12VDC did require some effort, because I wanted to retain the Tripp-lite charger-inverter and space is at a premium.

Third step was to install battery compartment heaters.  We do trek when the outside temperature is below 32F.  At that low temperature the internal battery management system (BMS) will not allow charging of the battery. This restraint was one of the reasons I resisted replacing the AGM batteries with a LiFePO4 upgrade.  

I decided that to have a useful LiFePO4 battery install I'd need supplemental heat in the exterior battery compartment. Otherwise, I would be restricted to warm weather trekking.  The fresh water system on the Roadtrek 210P is rated down to 14F, if specific steps are followed.  Cool weather camping will be determined by the weakest link in the chain.  I decided the batteries would not be the impediment. 

Approaches to keeping LiFePO4 batteries above 32F

Keep in mind that the batteries do generate some heat when discharging.  However, in an unheated compartment that is insufficient as temperatures fall, and the amount of heat is determined by the discharge rate.  In other words, batteries connected to a robust solar system do little self heating unless they are discharging, and the heat generated may be insufficient to keep the battery internal temperature above 32F.

There are two low temperature charging conditions to be dealt with:

1. While in motion, temperatures fall below 32F.
2. While stationary, temperatures fall below 32F.

It is possible to insulate the batteries, but that can create complications in hot weather conditions. So, while some compartment insulation is desirable, it must be used carefully in summer heat, which can reach 110F in the Southwest U.S. 

Today, one can purchase 12V LiFePO4 batteries with internal heaters.  The challenge with these is it is possible for the heaters to fully deplete the batteries if they aren't recharged on a frequent basis.  Of course, if one has sufficient solar panels, the battery heaters can run for extended periods while solar provides the necessary DC energy.

I decided that the most flexible approach was heaters external to the batteries:

1. One set would be powered via 12VDC when on solar or travelling with the alternator providing DC.
2. The second set would be 120VAC and would be powered via shore power or the generator.
3. In really cold conditions, all three heaters could be used if 120VAC is available.

Choosing the heaters

One thing I wanted to avoid was "hot spots" on the battery. Cooking the batteries is undesirable and dangerous.

I decided to use three heating pads, each independently controlled, with heat distributed.  I sized the wattage of the heaters using the SWAG method because I don't know the thermal contribution of the batteries as they are discharging, nor do I know the actual heat loss of the battery compartment.  I decided upon smaller wattages, realizing the inherent limitations. 

I can always increase the wattage of the heaters based upon experience. 

I realize that as ambient temperatures fall, there will come a situation that with the heaters on, the battery temperature will decrease below 32F and charging will be impossible.

The system

I did add some insulation.  Passive systems are preferred to active ones.

I'm using three independently controlled heating pads. Two are 12VDC and are intended to be used while the Roadtrek is in motion, or not on 120VAC shore power.  These can be switched off from within the coach, if it is desired to conserve battery resources, or if they aren't needed due to ambient conditions.

One heater is 120VAC and is intended to be used when the Roadtrek is stationary and on shore power.

Each heater is independently controlled, and On-Off settings are independently adjustable.  

I ran a system test today and the heaters worked as intended. Of course, the outside temperature is currently 68F.  The test was a functional test. 

The solar charging MPPT controller includes a temperature sensor. I've installed that in the battery compartment.  Of course, each temperature controller also has a sensor.  So, I'll have four sensors monitoring the battery compartment temperature.  LOL.  As I write this the compartment temperature is 68.1F.

The Challenges

Space in a Class B is very limited, as we all know.  I gave up my wine storage location for the temperature controllers.  LOL. 

Next..................

I may post a few photos once this is completed.

(c) N. Retzke 2022

Practical Solar

 

Making coffee in the morning in the "Solar powered" Class B
Must turn off the hot water heater before using the burner!
Outside ambient: 20F,  Inside: chilly!

Realistic expectations  

We trek and we have spent up to 100+ continuous days in our Roadtrek.  But first, we rented a "100% electric" solar powered Sprinter coach and took it to the National Parks in Utah.  It was mid-October 2013. Nighttime temperatures were about 20F.  It was a good test of how well a solar powered, electric coach would perform.  That was our purpose in choosing it, and I wanted to see how the BlueTec engine performed, etc. 

From a comfort perspective, it was not ideal, and G had to ask "How is it that one would spend $100K to buy this?" Adequate if the ambient temperature was in the range 50F to 80F and if one wasn't parked in the full sun during the daylight hours.  Otherwise uncomfortable. The Sprinter had sufficient batteries and solar, and a large inverter, but it did have power limitations. For example, we couldn't use the electric cooktop and simultaneously make hot water for bathing or cleaning. For comfort heat it had a 1500 W electric heater, which was not adequate at below freezing, nighttime temperatures. There was no propane. It was a Mercedes camping experience as we slept in sleeping bags.

However, that experience allowed us to make a more realistic list of "must haves" and after reviewing these and discussing the Sprinter and our experience, we purchased a Roadtrek 210P which uses multiple fuels for coach amenities.  After the Roadtrek financial bankruptcy, the 210P is no longer made, which is a shame. 

I'm not going to repeat my earlier posts, in particular the one about our experience and decision to purchase the 210P. I do have earlier posts on solar, batteries, etc. 

Solar Power and Batteries

We purchased a new Roadtrek a bit sooner than would have been ideal at the time. We were both working and had very limited time for trekking. On the other hand, the price in December 2013 was really good, with a steep discount.  So, we purchased it. Because we live in a HOA and our garage cannot accommodate the Roadtrek we had to store it, and the largest issue was keeping the chassis and coach batteries fully charged. I did run the generator monthly.  The 210P did not have solar.

To keep the chassis battery fully charged, I purchased a 50W solar panel and controller. That's documented in a earlier post. I selected a de-sulfating controller. That was in Spring of 2014. 

I mounted the solar controller adjacent to the coach batteries, and I decided I wanted a "portable" panel, because when it is hot it is preferable to park in the shade. My approach allowed us to charge the batteries during the day while we were comfy. The cable connecting the solar panel to the controller is about 20 ft long and is coiled and placed under the passenger seat when we are in movement.

The Coach Solar

The 24"  x 24" 50 watt panel is stored behind the drivers seat when we are travelling. Why only 50 watts?

I had evaluated our DC electrical power needs. Our Roadtrek 210P has a 2.8kW Onan gasoline generator. It also had multiple energy sources. For example, propane is the source for the furnace, hot water and a range top, as well as the third source for the 3-way refrigerator. All of the controls are 12VDC.

We have no interest in living "off the grid" for weeks while running the refrigerator and Air Conditioning or space heat using 3000 watts of batteries and solar panels. In fact, our 210P simply doesn't have enough roof space for all of those solar panels. 200W would be pushing the maximum roof space available. Our interest is charging the coach and chassis batteries, reducing but not replacing the amount of grid electricity we need and so on.  This is because of practical considerations. Those considerations include roof area available or size of portable panels, battery considerations and cost.

What can we get if we maximize the roof panel? For example, 100W solar panels can produce about 5.6A. Depending on the orientation of the panel, the intensity of sunlight and the hours of direct sunlight received in a day, a 100W panel can generate 20- to 30-amp hours (Ah) daily. In fact, the amount of energy may be only half of this because of clouds, panel orientation and hours of daylight. 200W could provide a maximum of about 60-amp hours each day. 

To charge the coach batteries using 120VAC and the Triplite charger-inverter requires anywhere from about 3.6A to 9.3A at 120VAC.  To fully charge 50% depleted batteries can take 12 hours.  At the lower charging rate using the Triplite 120VAC inverter-charger, 3.6A is a minimum used, or about 430 watts. I've measured the AC at the pole with everything off in the coach except charging via the Triplite.  At a typical seasonal campground where we pay $0.14 per kWh; that's $1.45 per day to keep the coach batteries fully charged. 

If the batteries are at 50% the AC required for charging can increase to 9.3A (1,116 Watts).   The 50 watt panel can't do that. It can provide about 4.2A at 12 VDC. 

The 50 watt solar panel is sufficient for my needs to keep the coach batteries fully charged under low load.   If we need more charging current I can run the Onan generator, or run the vehicle.  Running the vehicle will charge the chassis battery and, if the battery separator is closed the coach batteries will also charge. 

If we need more 120VAC than the 750 watt inverter and batteries can provide while off the grid, we run the Onan generator. The generator uses 0.3 gallons of gasoline at half load.  That's acceptable and in this manner we can recharge the coach batteries and run appliances. The Onan can provide sufficient AC for the heat pump/air conditioner. 

Why a Portable (detached) solar panel?

I preferred a portable solar panel because we can park the Roadtrek in the shade and put the solar in the sun, and I can orient the panel for maximum DC energy.  The de-sulfating solar controller I purchased is rated for 180W maximum panels.  I can always upgrade to more solar.  However, if I really want more solar, I'll probably mount a flexible panel on the roof and carry another 100W portable panel.  In that way I could get up to 200W if parked in the sun or, at a minimum 100W if parked in the shade with the portable panel in the sun.

I've written about batteries in earlier posts. I don't like the low temperature charging limitations of Lithium-Ion batteries.  Combined with the high cost, I don't see an overwhelming advantage for us. In my earlier posts I do go into greater detail about this.

50 Watt panel in full sun

Charging at MI campground

Coach battery voltage while charging in MI on 50W solar panel
Current (amperes) is not accurately displayed when charging;
the meter displays current draw (discharge) on the battery. 
While charging the current flow is in the other direction

50 Watt behind the windshield
The glass does reduce the efficiency, however, if facing the sun for half of the day the panel does keep the coach batteries fully charged. 

At the AZ "lily pad" the Roadtrek is under the roof.
  I place the portable solar panel on the roof.

The Roadtrek is in the shade, while the solar panel is directly above,
 on the the roof, in full sun.

Charging the Chassis Battery

The chassis battery also needs to be maintained.  My theft prevention device does increase the 12V DC power needs when the vehicle is stored. With the arrival of thin solar, or flexible solar panels I purchased a 30Watt for that purpose. The 30 watt panel can provide 2.5A at 12VDC.

The 30W panel can also be put inside, on the dashboard and facing outward.  This will charge the chassis battery when the vehicle is stationary and stored. 

Monitoring the batteries. 

I have two DC voltage indicators. One plugs into the accessory socket on the dashboard and it displays the chassis battery voltage. The other I added and is mounted inside. It provides coach battery voltage reading and current draw, when the battery is discharging. I added a power "Off-On" switch for the interior meter so as to conserve DC. I've included photos here. I have an earlier post on the coach battery monitor.

30 Watt solar panel

Chassis battery charging voltage on Solar, 13.1 VDC

(c) 2021 Roadtrek210.blogspot.com.