LT Organic Farm Waukee, IA

 

On our most recent trek, we made a stop in Waukee, IA.  While on an earlier trek we noticed the L.T. Organic Farm Restaurant and decided we wanted to stop in the future.  This was the opportunity for a late lunch.

It is a bit early in the season for the farm, but the restaurant was functioning.

G at LT Organic Restaurant

Serving

Our server explained the functioning of the farm and restaurant, their philosophy about food and also explained the meal.

It was delicious and G said it was the best meal of the trek.  We ordered a cheesecake portion "to go". 

For more about this establishment, visit their website.

Click for:  LT Organic Farm and Restaurant

The restaurant has interesting murals.  Here are two:

"Stress is good for immune health"

(C) N. Retzke 2022

What a difference a year makes

 

2,000 mile trek

We completed a 2,015 mile trek.  We left the cactus flowers behind, encountered snow and deer in the Raton Pass at 7,834 feet elevation.  I'll post some additional photos in a later blog entry.

Cactus Flower - Tucson

On to Trinidad, CO where we encountered more snow and deer attempting to cross the interstate! I took over driving at the Trinidad lookout point.

Scenic stop, Trinidad, CO

"Colorful Colorado" includes the guard rails.

Colorful Colorado - Trinidad

Early Morning - at Lake Michigan

Early Sunworshippers at Warren Dunes State Park

Observations

It seems that because of higher gasoline prices, some trekkers are hunkering down.  Some of the campgrounds were very full.  We made reservations and were never turned away. Some people exhibited keen interest in our Roadtrek 210P.  I had to inform them that this model is no longer manufactured.  However, there are used Chevy based Roadtreks available:

Roadtrek International Chapter FMCA "For Sale"

One year later, gas prices are significantly higher.  Last year this trek cost us $371.02 for gasoline.  In 2022 the gas cost for the same trek is $529.80. 

That's the equivalent of dropping from 15.54 MPG for this trip to 10.88 MPG.  We encountered some disgruntled people on the trek.  I don't understand.  About 51% of the voters decided to elect a guy with mush for brains.  Why should the other 49% be upset?  Oh, it was different when Trump was elected and the other minority created a Russian hoax and attempted to impeach him.  LOL. 

This morning at breakfast, the gentleman at the table next to us was wearing this hat.  There are some really angry people out there.  I'd say, it might be prudent to remove those "Biden-Harris" bumper stickers.  But as the saying goes "You can't fix stupid":

Demanding Reparations from Biden Voters

We arrived in Michigan and the nighttime temperature was 45F and it rained and rained!  We aren't in Arizona anymore, Toto!  We pulled out the electric blanket and turned on the heat.

The sun did come out and the prediction for today was a high of 90F.  LOL.  In fact, prior to leaving AZ, the "heat index" in DuPage County, IL was 104F.  Actually less comfortable than Arizona.

Today the forecast has been revised: high of 70F and sunny.  Tomorrow 83F, sunny and partly cloudy. Low tonight 60F.  

Trip Summary:

• Average gas price, per gallon: $4.37
• Highest gasoline price, per gallon: $5.049
• Lowest gasoline price, per gallon: $3.969 at Alda, NE.
• Total Miles: 2,015.
• Trip: 15.54 MPG (see Notes 1 and 2).
• Peak speed: 80MPH (short downhill stretch)
• Interstate speeds: 65-75 MPH (we did whatever prevailing traffic was doing).

Note:  

1. I used 88 Octane for 700 miles.  This probably contributed to enhanced mileage; it is well known that ethanol in gasoline reduces the MPG.  I did this because there are portions out west where one can choose 86 or 88 octane.  87 is recommended for the Chevy 6.8L engine so I bumped up to 88. Alternately, I could have alternated 86 and 88 at fill-ups. That would have blended to 87 octane in the tank.
2. Here's an older chart based upon U.S. Department of Energy data. It provides a rough idea of the drop in fuel efficiency at higher speeds. My highway speed is usually about 70 MPH (lower in 65 MPH speed zones, etc.).  I do my best to minimize idle time, which simply wastes fuel:

(c) N. Retzke 2022

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

Springtime in the Desert

 

Saguaro Cactus in Bloom - Saguaro National Park

With the arrival of 85F daytime peaks, or higher, the desert is blooming.  Birds are also mating and so there are a lot of activity.  I think the best times for wildlife viewing are at dawn or shortly thereafter.

Early morning the air is cool at 60F and the wildlife activity for the day is just beginning.  We see doves, raptors, woodpeckers and a variety of smaller birds in the National Park.  The larger birds pick a saguaro to perch on, while the smaller perch in Palo Verde's and shrubs.

On the other hand, the pollen count is quite high as Palo Verde's and a variety of shrubs and cacti are in bloom.

In the area, on the ground we see rabbits, lizards, and occasionally coyote and javelinas.  These generally avoid humans, so to see them one must be alert and stealthy. 

There is also a lot in bloom at the resort, and hummingbirds, too!

G and blooms in the resort

(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.

  

Charging a LiFePO4 Battery in the Roadtrek Class B RV

Tripp-Lite Charger-Inverter DIP switches and LED indicators

This precedes my recent post about the LiFePO4 installation.  However, it does include some of the groundwork.

The LiFePO4 battery arrived (April 1, 2022) , and I measured the terminal voltage.  It was 13.0V DC.  That's 30% State of Charge (SOC) for this battery.  The manufacturer's documentation states that the batteries "ship at 30% SOC". It's encouraging when the documentation matches reality.

My experience is, many RVer's overspend for what they "might" need.  That's true for RV battery and solar capacity, too.  Of course, if money is no object, then spend, spend away and when depleted, toss the junk into a landfill.

I think it is a good idea to read each manufacturer's specifications because there are variations and specifications should never be assumed from generalities. Matching actual charging parameters to the specifications is one thing that can be done to achieve maximum battery performance.  Ask the question: "Why is the battery rated between 4,000-8,000 cycles?"  Why that significant range?

Here's one example. In general, the recommended charge/discharge current is 0.5C for a LiFePO4 battery but "follow the manufacturer's guidance".  Higher discharge rates decrease battery life, which is to say, number of cycles of good performance.  For a 100Ah battery, 1C is 100A and so the maximum charge/discharge rate may be 50A. More on C rating later in this post.

If one wants to get maximum life from a coach battery, any coach battery, then adhere to the manufacturer's specifications for that battery.

Optionally, we can treat the coach batteries as throw-away AAA Duracell or Energizer batteries and deplete them and throw them away.  When we have money to burn, some RVers will do that, while voting to end "Climate Change".  LOL.

Battery Specifications

The LiFePO4 battery I purchased has these basic specifications.  (I'll post later about grades of LiFePO4 battery cells):

• 100Ah.
• Nominal voltage 12.8V. 
• 4000-8000 cycles life span.
• Removeable cover, replaceable BMS and cells.
• Recommended charge voltage 14.6V.
• Charge current 20A recommended, 50A maximum.
• Discharge current 100A maximum, continuous. Peak 200A for 3 seconds.
• Weight 28.2 lbs.
• 7 year warranty.

Nominal Voltage 12.8 VDC

The LiFePO4 battery has a "nominal voltage" of 12.8 VDC.  In fact, the voltage at the terminals can range from 10.0V to 13.8V.  

What's the value of knowing the "nominal" battery terminal voltage? The nominal voltage is used to calculate the watts or watt-hour capacity of the battery. Watts = Volts x Amperes, at the "nominal" voltage: 

• 1,280Wh = 12.8V x 100Ah

State of Charge - SOC

I provide a typical chart later in this post.  State of Charge (SOC) is another measurement. It states the present, actual capacity of the battery relative to its total capacity. 

State of Charge is in percentage: 

• 100% SoC means the battery is fully charged.
•  0% means fully discharged. 

 SOC is calculated this way: 

• State of charge (%) = Remaining Capacity (Ah) / Total Capacity (Ah).

Recommended Settings for the Battery Charger:

The battery manufacturer of the LiFePO4 battery I am installing in my Roadtrek has these charging recommendations:

• Charge (Absorption) Voltage 14.6V (14.4V minimum).
• Float Voltage: 13.8V preferred (13.6 Minimum).
• Charge Current 20A.
• Equalization: Off.

The battery manufacturer states:

• For optimal life don't discharge below 10% (About 12.1V).  To be more conservative, then don't discharge below 20% (12.9V).
• Recommended external Low-voltage disconnect 11.2V (About 6% capacity).
• Exceeding maximum current (50A) for charging can reduce the cycle life of the battery. 20A charging current is recommended.

Other Settings - Low Voltage Disconnect:

To protect the battery an external low voltage disconnect is recommended.  The internal BMS has a Low-Voltage disconnect >10.4v and BMS Low-Voltage recover >11.6v.

• Recommended external Low Voltage Disconnect: 11.2V (about 6% capacity remaining).

Why Follow Manufacturer's Recommendations?

Following the manufacturer's recommendations is how one may achieve 8000 cycles from these batteries.  I have concluded that it is possible to get 10 years of good performance from a LiFePO4 battery constructed of Class A cells. If one doesn't follow recommendations the battery performance will degrade and 4000 or fewer cycles may be the maximum achieved.  It is also possible to damage the battery.

Three methods of Charging

I have three methods for charging the batteries in my Roadtrek. Ideally, each method would provide the appropriate charging voltage and current:

1. Tripp-Lite charger inverter using 120VAC power (provides voltage and current control).
2. Solar using solar panels and a controller (provides voltage and current control).   
3. Engine alternator (simple voltage regulation, no control).

The first two methods can be adjusted to adhere to the battery charging specifications.  The alternator has no such adjustments.  To avoid over-charging the coach batteries I can use the battery separator to disconnect from the alternator and rely upon solar charging.  Alternately, a DC-to-DC charging system could be installed.  But there are practical limits to how much I'm willing to spend on this.

Battery C Rating and Charging

The Tripp-Lite is a 3-stage charger with a 4th equalize setting.  This is typical for lead-acid battery chargers.  

The LiFePO4 battery requires only two stages:  Bulk/Absorption are combined and there is a Float stage.  Using the equalize setting will damage the LiFePO4 battery, i.e. diminish it's capacity. So, the equalize setting of  the Tripp-lite must not be used.

It is very important that charger settings be matched to the manufacturer's recommended settings for charging the battery.

In the first stage the LiFePO4 battery is brought up to 14.4-14.6V at which point it is fully charged.  The charger should then reduce the current and hold the voltage constant.  The charge voltage will then be reduced.  In the final stage (float) the voltage is reduced to 13.6V.  

Typical 3-stage battery charging - Voltage versus current
Bulk, absorption (topping) and float stages
Bulk - voltage increases while current is held constant
Absorption - Charge voltage held constant; current varies as battery reaches full charge
Float - Battery resting - charging voltage is held constant and current reduced

To understand the diagram, charging current is expressed as a factor of C, which is the battery C rating.  The C rating is the measurement of current that a battery is charged and discharged at. The capacity of a battery is generally rated and labelled at the 1C Rate (1C current).   A 1C rate means that the discharge current would discharge the entire battery in 1 hour.  A fully charged battery with a capacity of 100Ah should be able to provide 100 Amperes for one hour: that's 1C.  For charging purposes, the C/10 rating is 100Ah/10A charge current which is 10 hours to charge.  The C/2 rating is 100Ah/50A charge current which is 2 hours to charge.  Charging times are approximate.  

The LiFePO4 battery manufacturer recommends charging in the range of 0 to 20A, with 40A permissible and a maximum of 50A.  Charging at 10A would be expressed as 100Ah/10 or C/10.  Charging at 20A would be expressed as 100Ah/20 or C/5 and at 50A it would be C/2. 

Setting up the Tripp-Lite 750-watt charger-inverter

Before installing the batteries, I checked the settings of the DIP switches on the Tripp-Lite. The Tripp-Lite is a 3-stage charger with a 4th equalize setting.  This is typical for lead-acid battery chargers.  

Charging Times, Approximate

One needs to decide how far to discharge the batteries prior to re-charging. If a minimum floor (minimum capacity before charging) voltage of the battery is 20% (12.9V) then the maximum battery life in cycles may be achieved. In other words, the amount of capacity used is 80%, or 80Ah of a 100Ah battery.  To replace that lost capacity at a charging at a rate of 20A would require about 4 hours to return the battery to full charge:

• 80Ah/20A = 4 hours to fully charge from 20%

The Tripp-Lite has two charging current settings.

1. Using the same 20% cutoff (12.9V) charging at a rate of 11A, which is one of two possible settings on the Tripp-Lite would require about 7.3 hours to return the battery to full charge:

• 80Ah/11A = 7.3 hours to fully charge from 20%

2. Using the same 20% cutoff (12.9V) but charging at a rate of 45A, which is the second setting on the Tripp-Lite.  That would increase the 120VAC draw on the 30A shore power, reducing power available for air conditioning, the microwave, etc. It is also higher than the battery manufacturer preferred 0-20A.  However, if this setting were used, it would require about 1.8 hours to return the battery to full charge:

• 80Ah/45A = 1.8 hours to fully charge from 20%

Possible Tripp-Lite Charger Settings:

1. The Tripp-lite was designed for lead-acid batteries but it can be used with LiFePO4 batteries which have a BMS. The Tripp-lite has two charging settings:

• "Wet Cell (vented)" (DIP Switch A1 in the DOWN position) and
• "Gel Cell (sealed)" or AGM (DIP Switch A1 in the UP position).  

2: The Tripp-lite has three stages for charging: BULK, ABSORPTION and FLOAT, but only allows us to select two of the charging voltage settings.  The "Absorption" and "Float" stage voltages are adjusted by selecting the battery type.  The charger doesn't allow us to set the "Bulk" voltage:

• Wet Cell: 14.4 VDC "Absorption", 13.5 V "Float".
• AGM: 14.1 VDC "Absorption", 13.6 V "Float". 

3. The BULK stage brings a battery to about 80% capacity using a constant charge current. See the diagram above. The charge voltage can vary in this stage.  

4. The Tripp-lite has two charging current rates:

1. 11 Amperes (DIP Switch B4 in the UP position).
2. 45 Amperes (DIP Switch B4 in the DOWN position).

These charging current rates would require this approximate time to fully charge a discharged battery:

• 100Ah/11A = 9.1 hours
• 100Ah/45A = 2.22 hours

Selecting the appropriate Tripp-lite settings:

These are the settings I used, which are closest to the battery specifications:

• DIP Switch A1 "Down"- 14.4V Absorption setting, which is the closest to the recommended 14.6V.
• DIP Switch A2 "Down" - Charger Enabled.
• DIP Switch B4 "UP"- 11 Amperes Charging Current.

Other Settings:

• DIP Switch B3 "UP" - Equalize reset (equalize off).
• DIP Switches B1 & B2 "Down" - No Load Sharing (Charge @ B4 ampere setting). 

Tripp-lite 750W DIP Switch location diagram
From the Tripp-Lite 932768 manual

Solar Charger

My 180-Watt de-sulfating solar charger has these presets. They are not adjustable:

• Charge: 14.2V (at 70F, voltage varies with temperature).
• Float: 13.4V (at 70F, voltage varies with temperature).

The solar charger is optimized for AGM lead-acid batteries and has a de-sulfating function.  That's not desirable for charging a LiFePO4 battery. LiFePO4 batteries do not suffer from sulfation. But they are sensitive to under voltage or over voltage. The solar charger uses a sensor to determine the charge voltage at various battery temperatures.  Charge voltage range 14.8V at 40F which decreases to 13.9V at 110F. The float voltage is also temperature regulated. Float voltage range 13.9V at 40F which decreases to 13.0V at 110F.

I'm inclined to replace this solar charger with a MPPT unit that can be adjusted to match the battery specifications. I'll be monitoring this to see if the charge voltage is close to 14.6V and meets the battery manufacturer's recommendations:

• Charge Current: 0 to 20A (not an issue with the size of my solar panel).
• Absorption Voltage: 14.6v preferred (14.4 Minimum).
• Float Voltage: 13.8v preferred (13.6 Minimum).

NOCO 3500 Smart Battery Charger

I do have a NOCO battery charger which is suitable for charging a variety of batteries.  6V, 12V and Lithium up to 120Ah.  It is a 3.5A charger, so it can take a while to fully charge a discharged battery. I have used it on a variety of lead-acid batteries, but never on a LiFePO4 battery.  It is an older "genius 3500" so it isn't designed to use with a BMS equipped battery. It has selectable modes for different batteries.  These include:

• Lithium Charging 14.2V, 3.5A. (29-hour charge time for a 100 Ah battery).
• 12V Normal Charging: 14.5V, 3.5A.

The battery manufacturer recommends a charge (Absorption) Voltage of 14.6V (14.4V minimum).  It seems the NOCO could get the battery to above 14.5V if I use the 12V normal setting. 

Note:  The newer NOCO genius5 and genius10 replace the 3500. These can charge at 5A or 10A respectively. The genius10 has this specification for LiFePO4 batteries:

•  "Lithium Charging 14.6V, 10A. For use on batteries with Battery Management System (BMS) only."

Initial Charge - Tripp-Lite and NOCO

I'll charge from 110VAC power using the Tripp-Lite before connecting the battery to the solar system or charging it with the alternator.

According to the charge status LEDs the Tripp-Lite the battery reached 91-100% before entering the float mode.  After disconnecting and a few minutes of rest the voltage at the battery terminals was 13.44VDC.  That's about 99% charged.

I decided to connect a NOCO 10A Lithium battery charger (14.6V) directly to the battery terminals with the coach disconnected. I wanted to see if it agreed and if it would continue the charging of the battery.  After allowing the charger about 15 minutes to settle I checked the status indicator on the charger. It was pulsing green:

• Pulsing Green LED - "Bulk charge complete, optimizing battery for extended life." 

The battery terminal voltage was 14.45VDC.  Apparently the Tripp-Lite did an acceptable job.

It was getting late. I decided to leave the charger connected overnight, to see if the battery could achieve a 100% charged condition:

• Solid Green LED - "When the battery is 100% charged, the Charge LED will be solid."

In the morning, I checked the charger. The LED was solid Green and the battery voltage was 13.83 VDC. The battery had apparently reached full charge at the specified float voltage.

Conclusion

1. I wrote this while evaluating the transition to a LiFePO4 coach battery.
2. I did decide to replace my older solar controller with an MPPT unit. 
3. This has been an educational experience. Since writing this post I have posted more about the installation.
4. The nominal battery voltage is 12.8, or 3.2V per cell.  However, a fully charged battery is about 13.8 V (3.45V per cell). A completely discharged battery is 10.0V (2.5V per cell).
5. Earlier modifications, including the volt-ammeter will be helpful.  I used the digital voltmeter to monitor the status of the charging and I intend to use it to monitor the battery capacity.
6. The Tripp-Lite charger seems to be capable of working with the LiFePO4 battery. It seemed to get the battery to about 99% charged condition before entering the "float" mode. That's okay with me.  I'll monitor the battery to get additional experience.  I'm inclined to rely upon an MPPT solar controller with settings to match the recommended battery settings.
7. My existing coach battery disconnect switch doesn't have the proper terminals to fit the new battery. I'll be purchasing a new disconnect.
8. A low-voltage automatic cut-off for the battery is desireable.  A low voltage alarm is also possible. Such a device would alert me to start the vehicle engine, or the generator to charge the coach battery. 

• I'd prefer to keep the battery discharge low limit above 11.2V.
• I do want to avoid discharging down to the 10.4 BMS cutoff. 
• I'd like to get that 4000+ cycles out of the battery.  
• I want this to be maintenance free (or reduced). With the voltmeter I installed in the Roadtrek I can easily determine the remaining capacity of a rested battery. 
• The discharge of the batteries overnight if parking/boondocking and with no AC power is the cause of my concern.

1. My $20 volt-ampere-wattmeter display works find.  I'm not inclined to replace it with a $90 gadget. 
2. I'll be monitoring the battery to see how it does when connected to the alternator and running the engine of the Chevy chassis. I seldom see a voltage higher than 14.4V.  I can use the separator to prevent the alternator from charging or over-charging the battery. 
3. Is there a better approach? One method to improve this arrangement would be to purchase a battery with blue-tooth(r) communications.  That could end any guess-work about the condition of the battery. Such a battery improvement isn't available from all manufacturers and could increase the battery cost by about $50 additional.  Of course, if one builds a battery a BMS can be selected which includes this communications feature. 

(c) N. Retzke 2022