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

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.

AGM Batteries Sulfation, RV AGM Battery Care and Charging - Part 2

This is part 2 about care of AGM batteries in a "motor home." The previous post is part 1.

After a significant amount of research into the chemistry,  technology and charging of AGM batteries I became concerned about battery damage including sulfation and freezing the battery electrolyte. I want to achieve longer battery life and have 100% rated battery power available when I am off the grid and am not running the generator. I decided I needed to make an improvement and installed a solar panel and solar controller-battery charger for my coach batteries. This post looks more closely at the research that led to my decision. I'll provide in brief the why's, as well as some of the "do's and don'ts." I am not promoting any product here. This describes the issues and the solution I chose, and provides background information about that decision. This may be helpful to others.

I chose a 50 watt solar panel and a "Solar Charger/Maintainer/Desulfator" rated for use with solar systems up to 180 Watts. The solar panel is not used when the vehicle is in motion. I decided on this approach because:

1. The replacement price of the coach batteries would be about $250.00-$400.00
2. The Camper Van may be stored for weeks and sometimes for months
3. It's desired to achieve the maximum life from the coach batteries
4. It's desired to have the batteries provide the maximum rated power throughout their life
5. When stored,  120V shore power is not available. Solar power is the only available power option unless the generator or vehicle motor is running.

The following post provides, in brief, what I have learned on this subject and how what I learned has influenced my decision  Why would I want to do this? I'd like to spare the reader the time to replicate what I have researched.

How to Achieve Full Life and Power from AGM Batteries
That is the goal. Get maximum power and longest life from the AGM coach batteries. Doing so should provide a more pleasurable trekking experience and reduce the annual cost of operating the camper van.

Deep Cycle AGM Batteries require complete charging, but not overcharging to achieve full lifespan, avoid freezing damage and provide the amount of power expected from them.

Roadtrek states in their 2014 210P manual "AGM Battery Warranty....... is voided if AGM batteries are tampered with, topped off with distilled water or allowed to sulfate or freeze due to lack of charge."

Here are the most important things that dictate battery life:

• Preventive maintenance
• Depth-of-Discharge (avoid discharge below 75% charged)
• Charging to a full charge
• Temperature conditions of the batteries (cooler is better). Batteries are designed for an average annual temperature of 77F (25C). If the average annual temperature is 95F (35C) then the battery life will be reduced by about 50 percent. 

What is full life? It varies. 3-5 years is fairly typical according to published information. However, AGM batteries are reputed to achieve up to 10 years if properly maintained, kept cool and if used in such a manner to maximize battery life. I decided I would prefer to replace these batteries every 6-8 years instead of every three years. I also decided I do want the maximum battery power to be available when needed.

Avoiding Sulfation and Extending Battery Life
Sulfation if left unchecked will kill the coach batteries. Sulfation begins when the batteries are not fully charged, and storing them unless "float charged" continues the sulfation process. The RT and most RVs include charging systems for the coach batteries. However, there are periods in which these 120V or engine and generator powered charging systems are not available. That is a problem. So how can I achieve my stated goal of long life at maximum power from these batteries under my actual storage and charging conditions?

Frequent charging while avoiding overcharging of AGM batteries will reduce, but not eliminate sulfation. Sulfation occurs each time a battery is discharged. Storing a battery is reputed to cause self-discharge and sulfation, and this is more serious at higher temperatures, above 75F.  Batteries which are not used weekly may experience sulfation.

Sulfation is the gradual coating of the positive lead plate of the battery with lead sulfate (PbSO4). Simultaneously the battery electrolyte, which is sulfuric acid (H2SO4) on losing SO4 molecules becomes diluted by water. This occurs during battery discharge. The chemistry is oxygen molecules (O2) from the positive lead plate combine with hydrogen molecules (H2) from the battery acid and the result is water (H2O).

Because AGM batteries are chemical devices, cold weather will slow the sulfation process while hot weather speeds it up. In other words, full charging may be more important at higher temperatures. On the other hand, as sulfation occurs battery electrolyte (acid) is diluted by water molecules and will freeze at lower temperatures than the normal electrolyte of a fully charged battery. Such freezing can damage the battery.

Normal charging does not remove all sulfate molecules from the plates. Over time they build up on the plate and ultimately contribute to the demise of the battery. Sulfation, or the formation of lead sulfate can permanently reduce battery capacity. If unchecked it can kill the battery.

Keeping batteries fully charged and reducing sulfation will extend the life of the batteries and provide optimum capacity. Battery life expectancy is directly the result of how well these batteries are maintained and how they are used (or abused). Key points are:

• Don't overcharge.
• Don't undercharge
• Keep fully charged and don't store undercharged.
• Use and keep the batteries at their average design temperature.  
• Apply a periodic full-saturation charge to de-sulfate the batteries.
• Don't over-deplete; reduce the average "depth of discharge." and avoid "deep discharge".
• Reduce the number of "discharge-charge" cycles. 
• Don't charge if over 120F and don't charge if the battery is frozen. 

Some of the above might not be possible. That is why many batteries don't survive for more than 3 years according to some published sources. However, I'm convinced that good care and attention to these details will extend battery life for most users. One manufacturer of battery chargers/maintainers/desulphators claims that certain models of their product "can more than double the useful life of new batteries." I can't verify that. However, it's prudent to ask why some batteries fail within 3 years while others go on for 6 or more years.

It is my understanding there are two types of sulfation: 1) reversible (soft sulfation), and 2) permanent (hard sulfation). Reversible sulfation is normal and can be corrected by a specific charging regimen. When charging, the PbSO4 is converted to lead and the SO4 combines with hydrogen to form electrolyte. Non-reversible sulfation occurs when a battery has been in a discharged condition, or "low state-of-charge" for a longer period, be it weeks or months. In such a state the sulfate crystals become permanent, cannot be reversed by charging methods and the capacity of the battery is permanently reduced and impaired.

Charging and Reducing or Reversing Sulfation
Special charging techniques are reputed to reverse sulfation.  Battery charging states include:

• Bulk (high, constant current)
• Absorption (constant voltage)
• Float (hold at 100% charge)
• Equalization.(controlled absorption overcharge)
• De-sulfation

A microprocessor "smart" charger will include three or four of these states. Special chargers provide a fifth state called "de-sulfation." One charger manufacturer declares "Patented high-frequency pulse desulfation is designed to reverse and eliminate battery sulfation."

There is some controversy about the claims of "reversing sulfation." One critic states "simple, electronic de-sulfation is a one size fits all approach." On the other hand, I've seen no comments or evidence that such pulse desulfation techniques can harm the batteries.

How to Apply a "Full Saturation" Charge
Such a charge is a general recommendation for lead acid batteries. However, some AGM battery manufacturers have specific requirements of this type of charge and if not followed it is possible to damage the batteries. This type of charge is also called an "Equalizing" charge. This is done by a deliberate overcharge of the batteries. The problem with sealed AGM batteries is there is no way to measure the electrolyte condition and so the equalizing charge is guesswork and may be based on terminal voltage. My guess is it's better to use a good 4-stage charger and avoid deep discharges.

Choosing a Battery Charger
The charger included in your RV or camper van is probably a three-stage "smart" charger which includes bulk, absorption and float stages.  "Float" charging is not "trickle" charging; a trickle charger can overcharge batteries!

I decided to add a "Charger/Maintainer/Desulfator" which was designed for use with solar panels. I also selected a solar panel which is overcapacity. This approach compensates for the lowered solar power that is available when daylight is minimized, such as during winter hours or when overcast. It also provides for a higher charging rate when there is optimal sunlight available.

Using a 50 watt solar panel provides a maximum 4.17 amperes of charging current at 12V during peak sunlight conditions. That's more than sufficient for maintaining or topping off the batteries.

Overcharging is to be avoided. I decided to use a solar charger that includes temperature compensation with float charging. The temperature sensor is attached to one of the battery terminals. This permits charging in cold and hot weather. The manufacturer states compensation works over the range 0F to 130F.

The solar charging system is only used when the batteries are not being charged via 120V shore power, generator power or via a running vehicle engine. It is intended to be used at any time the vehicle is stationary. The solar charger is connected directly to the batteries and operates independent of the position of the battery disconnect switch.

How Long Does it Take to Charge the Batteries?
The answer to that question is determined by the amount of sunlight available and the condition of the batteries. The purpose of the solar charger is to take the batteries from a condition of 85% to 90% charged to full charge, or apply a "topping" charge. Once at full charge, the goal is to "float" and desulfate the batteries while avoiding overcharge. Temperature compensation reduces the float charge as the battery temperature increases.

To bring a discharged battery to full charge can take 7 to 10 hours or longer. That is not the purpose of the solar system, but if there is sufficient daylight hours such charging is a possibility.

How Does "Depth of Discharge" Influence Battery Life?
Any AGM battery has a service life which is measured in number of discharges and the "depth of discharge." As a rule of thumb, the less the "depth of discharge" the longer the life of the battery, but it should be discharged to 90% peak when used. In other words, if used the battery should be discharged 10% and  a battery which is repeatedly used and discharged to 50% of its peak capacity and then completely recharged may be usable for 1000 cycles. If one cycle occurs each day, then the battery may have a life of 3 years.

That same battery, if discharged to 75% of its peak capacity each day and then fully recharged may be usable for 2000 cycles. Under such conditions the battery may have a life of 6 years.

Furthermore, that same battery if discharged to 25% of its peak capacity each day and then fully recharged may be usable for 500 cycles. Under such conditions the battery may have a life of only 16 months. Discharging a battery to less than 25% capacity is to be avoided.

What are Battery Storage Choices?
Batteries can be disconnected and then charged if they are not going to be used for long periods of time. It's best to store the battery in a cool or cold place (sulfation is slowed when it is below 75F). Here's a few methods:

1. Turn the battery switch "off" and then connect a 3- or 4- stage microprocessor controlled battery charger and fully charge the battery. If the charger includes an automatic "float" mode it can be left connected to the battery for long periods of time. Check your manufacturer. 
2. If the battery is fully charged connect a "float" charger, again check your manufacturer.
3. Alternately, the battery can be removed in the vehicle and kept above freezing while a float charge is applied. 

Avoiding the Freezing of Batteries
If the electrolyte in a lead acid battery freezes, the battery will probably be damaged. The capacity of such a damaged battery will be reduced. What are the freezing temperatures of a depleted battery? A battery in good condition that is 100% charged has the maximum concentration of sulfuric acid as electrolyte. As the battery discharges, the concentration of the acid is reduced as water molecules replace acid molecules in the electrolyte. Here are typical freezing temperatures for lead acid batteries at different charge states:

100% Charged = (-) 77F, or (-) 67C.
75% Charged = (-) 35F or (-) 37C
50% Charged = (-) 10F or (-) 23C

Other Sources
There are a lot of web based sources on AGM battery maintenance and charging. Enter  "AGM battery maintenance", "AGM battery charging" or "AGM Battery desulfation" in your favorite search engine and you'll get a list.

AGM Coach Battery Issues - Do It Yourself Solar Charging

This post looks at achieving the maximum life and performance from AGM batteries and also the steps an owner who doesn't have access to 24/7 120V charging power can take to keep the batteries in his/her "motor home" at full charge. It includes some of the background information I used to decide on solar power for charging batteries, and it includes a short video.

The Problem
Many motor homes and camper vans include coach batteries. Depending upon how many batteries are included and their capacity, they can be used for powering many things. Typical uses include the water pump, interior and exterior lighting, the refrigerator and small appliances via an inverter. Some motor homes include solar panels for recharging of these batteries. Some do not.

Absorbent Glass Matt batteries, or AGM batteries are very different from the old lead-acid and gelled electrolyte batteries. AGM batteries have a thin fiberglass mat or screen between the lead plates. The fiberglass mat is saturated with acid and is compressed and sandwiched between the plates. This tight packing makes the interior components tolerant of vibration. They are ideal for use in moving vehicles.  Many AGM batteries include bolt-on terminals which are reputed to give a more reliable connection.

AGM batteries are not cheap, but the best ones can last longer than other, less costly batteries. Perhaps 5 to 8 years if given proper attention.

As with all things, there are pros and cons. This post will look into some of these. Part 2 will delve more deeply into batteries. This post addresses the need to keep AGM batteries fully charged.

AGM - Are all Deep Cycle?
Not all AGM batteries are alike. Some are designed to be what is called a "deep cycle" battery and others are not.  So what is a "deep cycle" battery? Such a battery is designed to be discharged and recharged many times. "Deep Cycle" means the battery can be discharged to a lower level of peak capacity and recover. Some manufacturer's state that a deep cycle battery will last three to four times longer than a starting battery under the same conditions.

The batteries I am concerned about are deep cycle batteries.

Advantages of AGM Deep Cycle Batteries
If properly maintained, these are some of the advantages of these batteries:

• Improved resistance to shock and vibration
• Totally sealed
• Reliable
• No acid fumes
• No spilled acid
• No need to add water
• If fully charged can tolerate freezing temperatures (temperatures as low as -40F, but check with your battery manufacturer)
• Longer life as compared to a starting battery

How Do I Maintain a Deep Cycle AGM Battery?
That's a good question and as these are expensive batteries they do need to be properly maintained to achieve their full design life. These are sealed batteries so there is no water to add. Does that mean that the battery is "maintenance free?" No, it does not.

So what do I have to do? Most important is to keep these batteries properly charged! For motor homes or campers which are plugged in each day, this should be rather easy because these vehicles include chargers powered by the 120V shore power. Some vehicles charge the coach batteries when the vehicle engine is running. Others include solar charging systems. Some vehicles include all of the above and a gasoline or propane generator which can also recharge the batteries! However, sulfation remains a problem in lead-acid batteries. More on that later.

The two things to do to achieve long life from AGM deep cycle batteries are:

1. Recharge daily to a full charge.
2. Don't discharge too low. Don't fully discharge.

Is AGM Battery Maintenance Important?
Yes it is. Roadtrek has this statement in the current 210P manual:

AGM Battery Warranty Batteries are warranted by the battery manufacturer for one year from the "In Service Date" of the Roadtrek. 

1. Warranty is voided if AGM batteries are tampered with, topped off with distilled water or allowed to sulfate or freeze due to lack of charge. 

So there you have it. Owners must keep their coach batteries charged. Roadtrek has specific instructions about this for dealers, too. Here's two photos showing the stickers on a 2013 210P. The notice about the "Deep Cycle Gel Battery" is specific (this Roadtrek did have AGM batteries):

Charging AGM Batteries When Storing the Motor Home
For anyone who stores their motor home for long periods of time, there are only three ways to get the power necessary to charge the batteries:

1. Shore Power - 120V plug-in connection.
2. Solar Power.
3. Frequent vehicle or generator use. 

However, not all storage facilities include the necessary 120V power for charging, and not all motor homes include a solar power charging system. If you are like many who store their motor homes, you may not start and use the vehicle for two, four or more weeks. Is this a problem? Yes it is. So what to do? One possibility is to remove the batteries and charge them in your garage. However, that might not be easy as these weigh about 70 lbs. each. I decided the most effective method to allow storing the vehicle outdoors with the batteries inside was to install a solar panel and a solar battery charger. That's what I did, and I place the solar panel inside the vehicle when in use for charging. No rooftop installation required! A video is included in this post.

Solar Power Charger and Sulfation
When the batteries are not being drained by daily use, it's possible to keep them charged if there is sufficient solar energy (daylight) available. For anyone who only has access to solar energy during vehicle storage, this might be the only way for daily recharging.

Will using solar energy and a charger avoid sulfation and are there other issues? In a later post I'll give a more thorough description of what sulfation is. For now, suffice it to say that during battery discharge sulfate molecules (SO4) move from the battery acid (electrolyte) to a lead plate to form crystals of lead sulfate (PbSO4). This is called "sulfation." This interferes with the ability of the battery to perform. It reduces battery capacity, which is simply stated the amount of power a battery can provide. Less power means you run out of power for your camper van electrical devices sooner than expected.

A second problem is as the battery discharges the acid concentration decreases and the electrolyte changes slowly to water. This makes the battery electrolyte more susceptible to freezing. Freezing can damage the battery. Uh, Oh!

What Type of Solar Controller-Charger?
I decided to purchase a controller which the manufacturer states has the following features:

• Full-time automatic battery desulphation
• Uses US Patented pulse battery desulfation technology
• One year unconditional money back warranty and five year "no hassle" warranty on parts & labor
• Plug and run operation - fully automatic easy efficient operation
• Never over-charges - you can keep it plugged in for weeks, months, even a year 
• Temperature compensation - prevents over and under charging from freezing to 130 degrees
• Solar battery charger maximizes battery life and capacity and reconditions weak batteries. Maintains up to 2 batteries at a time. Short circuit, spark and polarity protection. 
• When used as a maintainer....is guaranteed to maximize your battery's life and storage capacity. 

Installation Issues
Finding a convenient place to install the controller and near the batteries can be challenging. The charger manufacturer states "....it is important the controller be in the same general temperature environment as the battery(s)." The temperature sensor lead length is not to be altered and that placed a further restriction. I decided I didn't want  a rooftop mounting of the solar panels at this time. I concluded that a larger wattage solar panel could be put on the dash to charge the batteries via a solar controller-charger. I decided on a 50 watt panel because this would provide sufficient power under lower light and reduced daylight hours, such as in winter or with the windshield not clean. It would allow the controller to charge the batteries even on overcast days. I also wanted simplified controller mounting and wiring.

The manufacturer of the charger-controller says this about mounting the solar controller-charger:

IMPORTANT INFORMATION ON USING PRODUCT OUTDOORS: Weather-tight enclosure. Always mount units in vertical position with cord sets exiting downward to ensure weather tight integrity. Unit must be mounted this way to ensure long term trouble-free life including weatherproof integrity. Mounting in any other manner or using unmounted (parallel to ground) except indoors may cause unit to fail due to water intrusion that is unable to drain correctly to avoid damage. 

Installing a Solar Charging System
So how to go about this? Three things are necesary:

1. Solar Panel
2. Solar Controller - Charger
3. Interconnecting cables

Here is a photo of the battery compartment of a Roadtrek 210P, model year 2013. It shows two AGM batteries. As you can see the battery compartment is very tight:

Here's a brief video of the installation of a Solar Battery Condition Charger and Controller with a 50-Watt solar panel: