The real problem happens when I'm driving on a long trip, I don't know how hot it is in the power cabinet or what the voltage is for the two batteries. As a result the refrigerator shuts off and could be off for hours until we arrive at our destination.

So why not take the easy way, install a 12 volt cooling fan and a switch?

Where's the fun in that!

Or I could come up with a very complicated solution that requires knowledge that I didn't possess.

I could be misquoting this but with my weak knowledge of science and philosophy let me give it a stab. William of Ockham is quoted in Ockham's razor; "When the solution to any problem has multiple correct answers the simplest is always the right choice."

Let me make this clear, when I started this project my total knowledge of electronics or Arduino could be written on a napkin with room for notes.

I gave myself two months to solve this problem or go for the easy answer.

The only hint that this might work was an NPR story I heard about these kids in Los Angeles who made an electronic device that played music using plants (or something outragious ). The reason for their success was they were able to use a new device that helps make complicated electronic things easy to learn and build.

I thought I had a 30% chance of success but I would learn a lot and that is worth something, right?

What is an Arduino Uno?

The Arduino UNO is a widely used open-source microcontroller board based on the ATmega328P microcontroller and developed by Arduino.cc. ... The board features 14 Digital pins and 6 Analog pins. It is programmable with the Arduino IDE (Integrated Development Environment) via a type B USB cable.

Did that help?

Most likely not. That's how I felt too as I opened the box.

Imagine telling your family "You can get me and Arduino Uno for Christmas" (I'm 68 years old). "So what is an Arduino?" they asked. I replied "I don't know but I might be able to make something with this thing."

What does my project do?

It measures the battery voltage, reads the temperature of the power cabinet, operates a cooling fan, as needed, and transmits this information to a second Arduino that displays the data on a screen so I can easily read it while driving.

I could go into a lot more boring detail about how this whole thing works but you really don't want to know. Suffice it to say it took two months and it works.

How was the success possible? I assure you that I stand on the backs of giants. After completing the initial Arduino training videos which gave me the basics I turned to YouTube. I discovered a subculture that I had no idea existed. The videos I found ranged from very helpful to crazy bad. It took a lot of patience to wade through hundreds of videos. What I was missing was structure and a foundation on computer programming and electronics. I found exactly what I needed on the web at "Programming Electronics Academy" https://programmingelectronics.com/home/ . In full disclosure, I have written computer code using Basic programming language 35 years ago. So I have some knowledge of how computer programs work. But it's kind of like knowing English and learning French or Italian. They all have similar structure but now I needed to know the words and their syntax. I finished the programming course in 30 days. Then I dove right in and three weeks later I had working prototypes. I packaged the devices in two 3D printed boxes and enclosed the sensors and the display in small housings that were also printed.