Nice read. He did leave a couple of things off but, the article puts things into perspective. The charts are nice for showing you how much things draw. He hit it spot on with the amp hours too.
He mentioned adding in a second alternator. What I think he should have mentioned was how much a low battery draw's. This is a key point in setting up a battery and charging system.
A dead or really low battery will draw around 40 amp's. Most modern vehicles run a 100-120 amp alternator. Your vehicle just driving down the road during the day will draw 20-30 amps. Lights and other things around 10 ish.
I like to say your stock system draws a max of 80 amps including the battery. Add in a second battery and your at 120 amp draw.
Your battery will draw less as its charged. What that means is 40 amp draw is when its low. Without doing the math, a battery with 80-90% charge draws around half that. I pulled those percentages off my head so they will be close only.
Putting this into English. It can take you 8 hours of driving to charge a low battery. If you run your alternator over 70% for that time, most likely, you will burn it out. Newer alternators do a better job and older are worse when it comes to what they can handle. If you take a deep cycle battery down to 20-30% (11.5-11.75 volts) It shortens it life. Dipping it down there occasionally is ok, all the time is not a good idea. Running your batteries almost dead really shortens their life.
My camper has 2 house batteries. I run 3 120 watt panels. My alternator is 160 amp. Before I got solar and LED's, I was good for 7-8 days with firing up the generator for the microwave and coffee pot. When I got home, depending on how far I drove, my batteries would be 80%-90%. If I camp in the forest with my panels shaded, they do very little. Some is better than none. Desert keeps them topped off and I don't have to depend on alternator. As I travel the highway, the panels charge. They average 30-35 amps. This takes load off the alternator. I almost never drive at night.
Alternators are not free power. The bigger the power draw the more horsepower they draw. Nothing is free.
My off road trailer has a single 120 watt panel. The little bit my lights and fridge take are put back in a couple of hours. I have not upgraded my landcruiser alternator yet. Charging that battery from low would not make my alternator happy.
Figure out what you draw and that will determine what you need. My little trailer would be fine with a smaller panel. I got a deal on it. The panels on my camper work out well. Because of forest camping, I could probably use another. No room though.
Scott
EDIT: I don't remember if the article mentioned this, when checking battery voltage, let the battery sit for two hours after charging. It needs to settle. Otherwise your reading will be high. This includes driving.
