New Voltmeter-Ammeter-Wattmeter for AGM batteries - Part 1

Earlier this year I replaced the AGM batteries in the Roadtrek with new AGMs. I decided against lithium (LiFePO4) batteries for the time being. For one thing, I hadn't decided which real estate I would give up. I wasn't sure I'd put them in the battery compartment as it is outside the rig and uninsulated.

I've posted on social media (G+ and FB) that I wasn't happy with the 4-point L-F-G-C "idiot light" arrangement in the Roadtrek, in particular because I discovered that the "G" or "Good" indicator was illuminated even when the batteries were below 50% depth of discharge (DoD).

What was my issue? It was about battery life and capacity. To get optimal life from AGM batteries most experts recommend not allowing the battery to regularly fall below 50% state of charge (SoC). The "G" or "Good" LED extinguishes below that level. The "F" or "Fair" light on the Roadtrek is below that. A simple plug-in digital meter was an option and one can be purchased for between $5 and $15. Here's one:

12V Plug-in digital Voltmeter

Our rental rig had such a simple meter, and I could plug one into the rear cabinet above the entertainment center in our 210P, which had a cigarette lighter for the 12V amplified antenna. I added a "Y" connector for this purpose. However, I also wanted an ammeter and a wattmeter, but I didn't want to spend the amount necessary for a Trimetric and I wanted something easy to install.

Here's the 12V connector I used to install a "Y" cable. That allowed me to connect a meter in addition to the 12V TV antenna amplifier. But viewing the meter in this location isn't very convenient.

Location of simple plug-in digital meter connector:

12V Connector in rear compartment

Installed and functional digital meter:

New Digital Meter

Battery Life Issues
All of this is really about getting full value and maximum capacity from the batteries. As AGM batteries age, they will lose capacity. Such batteries have specifications based on specific conditions, such as an ideal temperature of 77F. AGM batteries operate on chemical principles, and chemistry is influenced by temperature.

I had noticed that, after 4 years the batteries in the Roadtrek didn't seem to be able of providing the desired voltage for the time I wanted to use them "off the power grid". That indicated a loss of capacity.

The entire point of adding a digital voltmeter-ammeter is to get a better idea of the condition of the coach batteries. Even better than battery voltage is specific gravity, but that can't be readily determined. Below is a table for my current batteries which provides some idea of the life of the batteries when discharged repeatedly to certain levels of DoD (depth of discharge). As can be seen, the 50% DoD provides about 1200 charge-discharge cycles. Decreasing to 80% DoD provides a life of about 700 cycles. Avoiding DoD below 50% provides a good compromise between battery life (cycles) while providing adequate capacity.

The problem we face is that to extend battery life we either use them less (fewer cycles per year means more years of service before reaching end of life). Or, we can reduce the DoD. As noted in the table below, if the DoD is only 20% it is possible for a battery to provide 3600 charge-discharge cycles. Of course, to achieve only 20% DoD requires much less use of the available battery capacity.

Why Measure Battery Volts and Amperes?
How long can we run things in the coach on batteries and avoid discharging the batteries below 50% DoD? The ammeter and voltmeter with the tables for our batteries can be an aid to this.

For example, my batteries can provide 18.33AH for 12 hours. However, that is to 100% discharge, which is what I want to avoid. 50% DoD will allow a draw for only about half that time, or about 18.33AH for 6 hours.  Or, I could reduce the load and extend the time. If I really need to run solely on batteries for 12 hours, my batteries can provide about 9 amperes per hour:

                                           220AH/12H = 18.33A
                                           18.33A x 50% = 9.165A

The times are approximate. If we have an ammeter we can determine what the actual current draw on the batteries are. If we have a voltmeter. we can determine the state of charge of the batteries.

Battery Life and Charge-Discharge Cycles

Depth of Discharge - New AGMs

Using the Voltmeter
The digital voltmeter will provide an indicator of the state of charge (SoC) of the batteries. "OCV" is open circuit voltage, or the state when the batteries are not connected to a load:

Relative State of Charge @ 77F - New AGMs

Note that SoC tables may vary. Here is a "typical" AGM table, which differs from the chart above.

Typical AGM battery SoC table

Battery Life 
Taking care of batteries and extending their life will obviously reduce costs. They are expensive. 220AH of AGM batteries is about $450 to $600. However, the other desireable thing is capacity. I want to be assured that the battery is capable of providing the amperes I need for as long as I need them. A battery with reduced capacity may not be able to do that.

Capacity is the ability of a battery to deliver the amount of power it was designed to do. Over time, battery capacity will decrease. As the battery nears end of life, it's capacity will diminish significantly. The batteries I have are designed to provide 25A @ 460 minutes  (7.7 hours) when new. As the batteries lose capacity, they will provide 25A but for shorter periods of time. And as the battery discharges, the voltage will decrease. A battery with diminished capacity will experience more rapid voltage fall-off. DC power is volts x amperes. As the voltage diminishes, so does the power if the amperes are constant.

While extending battery life does reduce operating costs, I am more interested in having the desired capacity available to me.  My batteries are rated 220AH. That means that they can continuously provide about 18 amperes for 12 hours, if they can provide full capacity (see notes):

220AH/12H = 18.33A.

Real World Capacity
The capacity achieved is based on battery condition, ambient temperature and other factors.

As noted above, the 12 hour rating for my AGM batteries is 18.33A.

In the real worlds AGM battery capacity does gradually decline, and by 700 cycles capacity decrease to 50-60% is usual. That means that the above number will gradually decrease:

• New AGM battery (80-100% capacity) = 18.33A for 12 hours
• Battery after 400 cycles (80% capacity) =  14.7A for 12 hours.
• Battery after 700 cycles 50-60% capacity = 9.2A for 12 hours

Lithium batteries also have a gradual reduction in capacity, but generally a 220AH battery:

• Lithium battery after 400-500 cycles (80% capacity) = 14.7A for 12 hours. 

Note: The above numbers are based on battery manufacturer published data and this information does vary from manufacturer to manufacturer. It is important to realize that battery data is usually under ideal conditions such as 77F temperature. AGM battery capacity decreases as battery temperature decreases and can perform (charge and discharge) over temperature ranges of (-)4F to 104F. Lithium batteries generally can operate with charging temperature of 32F-113F and discharge temperatures of (-)4F to 140F. Electric vehicle and experimental data indicates that high environment temperature could accelerate the aging of LiFePO4 batteries, while low temperature could reduce output power capability. Data suggests normal life can be achieve if operated in the range 50F to 104F.
However, it is important to check with each manufacturer for their specifications.

Battery Life based on Depth of Discharge
A well maintained AGM (absorbent glass mat) battery has a life of 6-8 years. Average life has been stated to be 3-5 years. If not maintained, that will diminish to 2-4 years. Note that it really is charge-discharge cycles that are the limit. Battery manufacturers assume a certain number of such cycles in a year. That assumes optimal temperatures of 77F and that the batteries are immediately charged to 100% immediately upon the end of the discharge cycle.

For example, with 50% DoD my batteries are designed to provide 1200 charge-discharge cycles:

1. If used every day, a battery will experience 365 cycles per year.  Under such use, the batteries have a service life of 3.2 years. 
2. If a charge-discharge cycle occurs every other day, or about 180 times a year, the same batteries could provide a service life of 6.7 years. 
3. If a charge-discharge cycle occurs every three days, or about 120 times a year, the same batteries could provide a service life of 10.0 years. 

 For example, with 80% DoD my batteries are designed to provide 700 charge-discharge cycles:

1. If used every day, a battery will experience 365 cycles per year.   Under such use, the batteries have a service life of 1.9 years.  
2. If a charge-discharge cycle occurs every other day, or about 180 times a year, the same batteries could provide a service life of 3.9 years. 
3. If a charge-discharge cycle occurs every three days, or about 120 times a year, the same batteries could provide a service life of 5.8 years. 

How does one "maintain" a maintenance free battery?

1. Recharge as soon as possible after use - preferably within 24 hours.
2. Recharge the battery properly.
3. Use a "smart" charger.
4. Battery should not be charged if the core temperature reaches 120F (49°C).
5. Avoid discharging below 50% SoC (state of charge).
6. When recharging, recharge to at least 80% SoC before beginning another discharge cycle. 
7. Charge to 100% as often as possible. 
8. Avoid heat; heat shortens battery life. Each 15°F (8C) rise in temperature reduces the life of the battery in half.
9. Know the correct state of charge (SoC). Knowing this will help to extend overall cycle life. A battery monitor is worthwhile and use one that is accurate.  

Battery Cost 
There is a cost to overtaxing batteries, as noted above. Best case is a battery with 50% DoD, and that yields 1200 cycles under best conditions. As noted above:

1. If used every day, or 365 cycles per year or a service life of 3.2 years.  The cost is $140 per year ($450/3.2)
2. If a charge-discharge cycle occurs every other day, or about 180 times a year, the same batteries could provide a service life of 6.7 years. The cost is $67 per year ($450/6.7).
3. If a charge-discharge cycle occurs every three days, or about 120 times a year, the same batteries  could provide a service life of 10.0 years. The cost is $45 per year ($450/10).

 For example, with 80% DoD, which provided more AH, but sacrifices battery life:

1. If used every day, a battery will have 365 cycles per year.  At 80% DoD, my batteries are designed to provide 700 cycles.  Under such use, the batteries have a service life of 1.9 years.  (Cost is $236 per year)
2. If a charge-discharge cycle occurs every other day, or about 180 times a year, the same batteries with a life of 700 cycles could provide a service life of 3.9 years. (Cost is $115 per year).
3. If a charge-discharge cycle occurs every three days, or about 120 times a year, the same batteries with a life of 700 cycles could provide a service life of 5.8 years. (Cost is $78 per year).

Notes: 
Ampere-Hours. An amp hour (AH) rating is a rating usually used on deep cycle batteries. It is an ampere rating taken for 20 hours. For a 100 AH rated battery a load may draw 100AH from the battery for 20 hours.For such a battery, that's about 5 amperes an hour. 100AH/20H  = 5A).

1. The total time of discharge and load applied is not a linear relationship. As the battery load increases the actual capacity decreases. For example, a 100 AH battery with a 100 amp load should provide one hour of runtime. But it won't. The capacity of the battery will be severely reduced.
2. Each battery manufacturer provides AH data under various loads. For example, here is the table for my batteries, with a final voltage of 1.75V per cell (3 x 1.75 = 5.25V, or a dead battery):
1. 20 hours = 220 AH
2. 10 hours = 210 AH
3. 5 hours = 190 AH
4. 3 hours = 175AH
5. 2 hours = 155 AH
6. 1 hour = 130 AH

Using the AH from the battery table, a rough guide for capacity can be determined. For example, 10 hours = 210AH. To achieve a 50% DoD, 210 x 0.5 = 105AH realized capacity. To achieve a 80% DoD, 210 x 0.8 = 168 AH realized capacity.  However, these figures are approximate and are based upon a new battery and 77F. The approximate condition (state of charge, SoC) can be determined with a voltmeter.

Using the above, the 10 hour ability of the batteries is actually about:

10 hours, 50% DoD = 105AH/10H = 10.5A.
10 hours, 80% DoD = 168AH/10H = 16.8A.

Note that the above information is in accordance with the battery data provided by the manufacturer of my batteries. The actual data will vary by manufacturer.

August 10, 2017 added and expanded "real world" battery life data.

Keeping cool in summer heat

Well, it is that time of year again, and the sun is beating down on some of us. One challenge is to keep cool, and keep that refrigerator running. A couple of years ago we were trekking in TX and hit 103F heat. We really weren't prepared.

We've done a few things to help us. Some are the same things others have done and based on my observation, some are not.  Of course, one thing is to park in the shade if possible. However that may be easier said than done. So if we have to park in full sun, then what? How to keep our Roadtrek from becoming a sauna?  The Duo-Therm Cool Cat heat pump works really well, but it does need some help when the sun is bearing down upon the front of the RT.

Here's a few things we have done to aid us in keeping cool in our RVs.

Reflectix
A bubble wrap reflective foil in windows has been a big aid, particularly in the Roadtrek, our class B. That has a large front window which simply seems to pull the heat into the vehicle. Reflectix has been very helpful. We use it in all windows except the side entry in summer and fall/winter trekking. Glass has a R-value of about 0.1 which means almost no insulating value. I understand that Reflectix has an R-value of 1.0. I understand the Roadtrek has an R-value in the walls of about 4.5. Anything we can to to improve the insulation is a good thing.

Screens
The Roadtrek came with side entry and rear entry screens. When the outside temperature is acceptable, if we can get better airflow that is an aid. However, we prefer to close the side door. I fabricated a magnetic held screen for the front side window. These can be purchased, if one prefers. The goal is to get the interior temperature down to the exterior without the use of air conditioning. We open the side window a couple of inches and use the Fantastic Fan, or open the rear door which has a full interior screen.

Fans
Our RVs have roof fans. These include Fantastic Fans. That's helpful for pulling warmer interior air out, and drawing in cooler outside air, when it is available. Or, after a shower, these fans can move moisture laden air to the outside, reducing interior humidity.

However, we also use a 12V DC fan in the Roadtrek, We found one that sits on the shelf above the side door. It has side air inlets and variable speed. Very helpful to move air around in the front of the RV, particularly if the vehicle is facing the sun.

A small 120VAC fan is also useful. This we use in the travel trailer to move the air around. Got a small 8 inch diameter Vornado which is also variable speed.

Create Shade
If one can't park in the shade, the next best thing is to create it. Many rigs have an awning, and if possible one might be able to orient the position of their RV so they get some benefit. Creating partial shade is easier than it may seem. We use several sun screens to aid us. One we fabricated from a roll of Coolaroo material. We hung that one the side of the TT which gets a lot of afternoon sun. It made quite a difference. We purchased a triangular piece and we position it as necessary with the Roadtrek. Usually to the front. I use a couple of expandable metal tent poles and 1/8 inch green nylon rope with tent stakes to get it into place. A 36 inch wooden dowel holds the front up to keep it off of the vehicle. I use aluminum carabiners to attach the sail to the tops of the poles. This allows me to quickly drop the sail if the wind comes up, or when evening approaches. The lines are strung to stay in place and hold the poles up with the sail dropped.

Here's the Roadtrek with awning extended, reflectix in the front window and the coolaroo sun sail up.

When not in use the sun sail folds conveniently and with the tent poles goes easily into the side storage compartment of the Roadtrek.

The travel trailer gets a lot of side sun in the dining/living slide. We hung a piece of coolaroo fabric. I used the coolaroo lacing kit to clean up the cut fabric ends. A custom wooden clamp the full length of the top keeps it in place. I fabricated a spacer to keep the upper area of the shade off of the side of the trailer. The spacer is made from a chromed shower rod and foam pipe insulators. That space is important to keep an air gap along the entire length of the shade. 

I use a couple of clamps designed for that purpose on the bottom with a bungees at a slight tension to hold the bottom out from the RV.  I attached the bungees with 1/8 nylon cord to a couple of bricks.

Cover the Roof Vents
A Maxxair vent cover is nice. It keeps the sun from directly striking the lid of the roof vent and it keeps bugs and birds away from an open vent. We added one to the Roadtrek.

However, the previous owner of our TT didn't install these covers and it has three roof vents. While on the roof I noticed that the covers were showing some distress after being in the sun for about 6 years. We also noticed a lot of heat in those areas during hot sunny days. One can install a insulator.  Camco has one which has a bright aluminized surface, which can be pointed up. These aren't very convenient if one wants to open the vent lid frequently. However, in cool weather we use one in the bedroom to keep the heat inside and provide some insulating value.

I decided to cover the vent covers with heavy duty aluminum foil. That reflects the heat away from these covers. It really made a difference in the travel trailer. I used a tube of exterior silicone caulk and after applying a bead on the edges, sides and in a pattern along the top I simply placed the aluminum foil and smoothed it into place. I trimmed the foil and folded the edge under the vent cover lid.  The travel trailer has 10 windows and frosted glass in the doors, so we get ample light even with the vents opaqued.

Camco vent insulator, aluminum side up:

Refrigeration
Our Roadtrek has a Dometic 3-way absorption type refrigerator. When we first encountered 103F we were on a site with the refrigerator side of the RT in full sun. The refrigerator had some difficulties keeping things sufficiently cold.

We had one of those battery operated fans and it was useful. An internal thermometer mounted on the top shelf told us the real condition inside. I did some research and read the Dometic manuals about "Power Ventilator Installation" and concluded that improved ventilation would be helpful. I added two very low power 12V DC fans and a thermostat with an in-line fuse.

Refrigerator interior fan

Ventilation Fans

Refrigerator Thermometer

Tire Carrier Surface Finish Issues - Rust!

Yakima Bike Carrier - No Rust after 10 years

The photo above is not directly related to the issue with the tire carrier finish. But this is the best place to put it on the blog. I added this photo of the bike rack on the rear of the Roadtrek. It is a Yakima "KingPin 4" which can accommodate up to four bicycles.  We normally travel with two.

The Yakima shows no rust, after 10 years. It has a powdered finish and Yakima obviously does a great job. No rust of any kind on this bike carrier after about 11 years!

I purchased this adapter in 2006 for our Malibu Maxx and use it on both vehicles. I added a hitch adapter to match the hitch on the 210P to the 1-1/4" hitch on the bike rack. This moved the rack out.

As shown in the photo, I can open the right rear door of the Roadtrek with the rack on the Roadtrek. Very convenient.

Comments March 1, 2017:

1. A reader suggested I consider using "Corroseal" which is a rust inhibitor.  Thanks for the tip, Wanda!  "Corroseal® is a water based rust converter combined with a non pigmented high quality latex metal primer. The converter segments turn rust into a barrier layer of black non rusting magnetite. The metal primer acts as a bonding agent for oil-based intermediate and finish coatings of epoxy, enamel, acrylic, polyurethane and moisture-cured urethane...."  http://www.corroseal.com/technical/technicaldata.aspx
2. I used Rust-Oleum® Stops Rust® Rusty Metal Primer. According to the manufacturer this "stops rust and prevents corrosion. Apply to heavily rusted metal (use Rust-Oleum® Stops Rust® Clean Metal Primer on clean or lightly rusted metal). Bonds tightly to rust to form a surface top coats can adhere to."

Original Post February 27, 2017
The surface of the metal tire carrier on my 210P began to show some distress about two years after purchase. Paint flaked off to show rust underneath. This became quite extensive by the third year.

I really don't know what grade of steel, or surface finishing was used. It appears that there was no metal primer, but that is difficult to determine. Let's just say that the black paint and the primer were identical, because the paint flakes were black throughout, with rusty metal beneath.

I prepared the surface by cleaning with mineral spirits. I then used a stiff wire brush and a wire wheel to remove as much loose or flaking paint as possible, and also removed as much surface rust as I could. However, it would take a lot of grinding to get to polished metal. I also did not want to disassemble the unit.

Here's what it looked like after the first pass of cleaning. The first was by hand with a stiff wire brush, to remove as much loose paint as possible:

Here is how it looked after using the wire wheel with a 3/8 drill and before cleaning. Soon I'll be applying a primer:

After doing this I cleaned the surface again with mineral spirits, allowed to dry and then with a tack cloth. I did have to open it and flip it several times, and I used a wooden shim to keep it from closing (going to a 90 degree position).

I wanted to assure that all loose rust and paint had been removed. I decided against using a spray primer, choosing a brush-on "Rusty metal primer". I painted it partially on a table, let that dry overnight and then completed by sliding it partially into the center hitch of the Roadtrek:

I let it dry in the horizontal position, then closed it partially and that allowed me to paint other areas. I used a wooden shim to hold the hitch in position (shim removed for this photo):

I used brush-on black enamel as the final coat of paint. I used a shim to hold the rack in the partially dropped position. The arrow in the photo points to the shim, which is a piece of scrap with partially black surface:

Here's the finished tire rack. I didn't put a finish coat on the section that slides into the receiver; it will simply be scraped off when inserting it:

While I was at it, I painted the hitch parts on the Roadtrek that were showing some rust. Same procedure as the rack; clean, wire brush, prime and then finish coat.

We'll see how well this does. I hope it slows the rust down.

Coach Battery Replacement

My Roadtrek which I could name "Tried and true" or "Rock steady" continues to perform. But there is maintenance to do. Some of this is preventative.

It became apparent that I needed to replace the coach batteries when one of them dropped to 0 volts. It had shorted, I guess, because the bank was at 6.5 volts, which was the voltage across one of the batteries and also the voltage across both. One battery seemed to be doing okay and the other was a tag-along. Just like America, 50% are doing the work and the other 50% is contributing nothing. beyond lip service.

I was aware that the batteries were not able to deliver the designed capacity. Capacity is the ability of a battery to provide the required power (watts) or ampere-hours for the required amount of time. My coach battery capacity prior to the 0 volt failure was below 50%, even though they measured suitable voltage on the indicator in the Roadtrek.

My batteries achieved a life of 4 years. Well maintained AGM batteries can go for 6 years, or more. I use a 50 watt solar panel with de-sulfating controller to maintain the batteries when off of the grid. My measurements indicate this is sufficient when storing the Roadtrek. On a sunny day the batteries will reach peak voltage. After a couple of cloudy days the voltage might decrease to about 80% as an indicator of "state of charge." I take my measurements early in the morning, prior to sunrise and after sufficient time to dissipate any "surface charge."

I'd done a lot of research including opening a discussion via the FMCA Roadtrek International "cyberrally" email.

I'd also designed a LiFePO4 system, should I want to upgrade to a lithium battery system. However, I decided at this time that going with AGM battery replacement was the prudent thing to do. More on that decision in a future post.

I was spending some time in the Tucson AZ area, so I found a distributor who carried the 220Ah 6-volt AGMs I was interested in and would install them for an additional $30. The total price was irresistible.

One thing we observed was the ends of the crimp connectors showed some oxidation. Is that a problem? The oxidation is higher resistance than bright copper, and over time that oxidation will creep up the wire. Resistance is a voltage loss and a source of heat. After cleaning, the ends were again shiny copper.

The installer then applied liquid plastic via a glue gun to seal the end of the connector. This should prevent further oxidation.

The new batteries included lifting means. One of the reasons I didn't do this was the fact that the old batteries didn't have such a means. I was faced with either purchasing a strap, or wrestling with 63 pound batteries. I've stored the lifting means in the compartment with the batteries.

Here's the completed installation:

After several weeks of monitoring the battery voltage, and with the solar panel connected, it seems the new batteries are doing well, achieving maximum terminal voltage and sustaining it into darkness.

My Roadtrek which I could name "Tried and true" or "Rock steady" continues to perform.

Homemade Freezer Thermometer

In the TT we leave some things in the refrigerator. It is a absorptive two-way which uses 120VAC when available and propane/12VDC if AC power isn't available.  We leave the TT at a site unattended sometimes for a couple of weeks. But we don't empty the refrigerator and it is in the AUTO mode. We take all meat items or high spoilage stuff out when we leave, but condiments, bread, peanutbutter, soda, wine, frozen veggies, cheese, etc. are left cold.

We are counting on the refrigerator switching from 120VAC to propane/12VDC in the event of AC power loss. That has worked fine and will work as long as the battery and propane are available. However, there is always the possibility that something will go wrong.

We use a simple memory thermometer for the freezer. We filled a 3 ounce plastic cup with water and placed it in the freezer. We also placed a quarter in the freezer. This prepared the thermometer.

Several hours later, we removed the frozen cup and quarter. We placed the quarter on top of the frozen water. Then we put it into the freezer.

If the freezer begins to thaw, the ice will turn to slush and the quarter will sink into it. On return to our TT we simply check the freezer. If the quarter is resting on top then we know the freezer temperature has never warmed above 32F.

RV Refrigerator Tweaks

It’s getting warm and I see more and on the social websites about complaints or issues about RV refrigerator performance. There are some things that one can do without voiding warranties or spending serious cash.

What type of refrigerator? Some of the newer rigs have 120VAC compressor refrigerators (residential models) with big batteries and a large inverter (12VDC in/120VAC out) to power the refrigerator when trekking down the road and off of 120VAC shore power. Our 5th wheel (HB#3) has such an arrangement. The TT (HB#2) has a larger absorptive refrigerator with separate freezer and refrigerator compartments. We don’t trek in it so it runs on 120VAC.

Our Roadtrek (RV #1)) also has an absorptive refrigerator. It’s a single door model 5 cu. ft. We do trek in it and so we do run it under a variety of temperature extremes, and on 120VAC as well as propane/12VDC battery. It’s a good size but not as large as the one in the TT. We use the Roadtrek refrigerator to transport initial food to the summer camp (HB#2) and of course when on our treks (longest to date was 110 days). The refrigerator has performed well, but we decided to make some modifications to help it out under high ambient temperature conditions. This post is primarily a consequence of our experiences in the Roadtrek with treks from 2 weeks to 110 days.

There are some things to know about the absorptive type of refrigerator. Adapting to what we’ve learned makes our treks better. ‘Better” as in more successful or easier. I suspect some of our lessons learned would be helpful with any style or model refrigerator.

IMHO having a good time means learning to live within limitations. That might be our financial means, our time constraints, or the limits of the available technology. One can resist or one can adapt. It’s all a matter of choice. I prefer successful treks and so I learn and adapt.

1. The absorptive type of refrigerator is slow to cool. That means turn it on and give it some time to reach 45F. If the refrigerator is 90F when you turn it on, don’t expect instant frost. Sounds simple, but you would be surprised what people expect. It also means put cold things in it to give it a boost. Put warm things in a warm refrigerator and one can expect soured milk. What can we do to avoid this? Start up the refrigerator several hours before first use. How early? The warmer the refrigerator is when you start it up, the longer it will take to chill. Use common sense. As an aid we also put a large, frozen ice pack in the freezer when we pack it for a trek. That works very well. See the photo.

2. On hot days don’t park with the sun striking the side of the RV that the refrigerator is on. The additional heat from the sun is sure to create efficiency problems for absorptive refrigerators. We travel with a triangular sun sail to shield the RT from the hot sun.

3. Do what one can to help the refrigerator. We load it up with fully chilled goods before we trek, and that large ice pack.

4. Once on the road we minimize the bulk addition of warm items, and prefer to add these only in the evening when the ambient temperatures are falling. For example, we only add 2-4 cans of warm soda or sparkling water at a time. When we shop, we put the coldest things in a small cooler, to keep them cold. When we introduce them into the refrigerator there is less “heat shock.”

5. Use an interior fan. There are battery operated ones, and fairly inexpensive wired 12VDC fans. We opted for the battery powered simply because our refrigerator doesn’t have an interior light, or some easy means to get to 12VDC power.

 6. If you are planning on travelling in elevated temperature areas, add exterior, supplemental fans to draw air into the compartment behind the refrigerator. This we decided upon when we experienced the consequences of daytime temperatures consistently above 100F.

Here's the sun sail mounted to shield the front of the vehicle. if the sun was on the refrigerator side, we'd position it to provide shade on that side.