I don't understand how your battery stays above 80% SOC from a 100 W solar panel without having a separate source of recharging.
Everything I have read about 12 v refrigerators leads me to believe that the 24 hour power consumption is 30Ah - 40Ah (depending on manufacturer and model) in 70 - 80 degree weather and higher in hotter weather.
Looking at some manufacturer specs for electric blankets shows they draw 3 - 4 amps per hour. So 3 hours would be 9Ah to 12Ah.
Not counting the power to run the fan from the heater, roof vent fans, internal lights, periodic use of a water pump (if you have one), recharging phones and other devices. It seems your daily consumption would roughly be between 40Ah and 50Ah a day.
With clear skies and a well pointed panel a 100w solar panel will produce 30Ah - maybe 35Ah a day at best.
Seems to me even in ideal conditions the panel would be barely recharging the battery if not slightly falling behind everyday.
Consumption of around 40Ah per day is consistent with our experience in our camper on late spring through early fall use. We need more power in early spring, late fall and Winter. We originally had a 100W panel. When we experienced cloudy days or rainy days the panel could not recharge the battery every day and it got lower and lower.
I looked at adding a second panel and found that a single 300W - 350W panel was marginally more expensive than another 100 W panel and that the weight of the single 350W panel was less that two 200W panels.
I am talking about rigid panels. I am not aware of any semi-flexible panels over 270 W. Also, a good quality 200W semi flexible panel is close to the price of a 350W rigid panel.
I made the conversion several years ago when semi-flexible panels were frequently failing within 12 - 18 months of purchase so I decided to stay with a much more reliable rigid panel. I have read accounts that the semi flexible panels are better now but I still read about early failures of flexible panels.
What am I not understanding is how a 100W panel can keep your battery from dropping below 80% SOC, assuming the power consumption values above are close to correct (and perhaps they are not - but I would then like to understand what the power consumption actually is) in any situation other than parked with no shade and no clouds in late spring through early fall when the sun is still high in the sky.
This question is posed mainly so people who are thinking about their setup can better understand the details.
I think it is better to have plenty of power with some margin (for the successive cloudy days) than not enough. If you add additional devices to your camper (or camping), such as electric bikes, a drone, a computer, etc, that require power, there will be power available without having to upgrade the solar charging system (again).
Good questions, ckent. Clearly we are on one side of the bell curve for power usage. My post didn't answer the original poster's question, so sorry for the thread drift. (I'd probably get just one panel, might as well get as much wattage as you can afford).
Our fridge usage is based on almost 500 nights out, mostly Oct-May but a lot in southern California deserts. I haven't calculated amp-hour usage for it. It seems to turn on a lot. Some of the days when out hiking it was really warm. A few weeks ago it got up to 82F, but it was sunny. Our solar easily kept up while wandering all day. Perhaps we spend more time outside the camper with just the fridge using power than other folks? Hard to say -- everyone is different. Also we have the small 65 liter fridge, usually set at 1.5 or 2.
We don't have some of the other gadgets you mention except we sometimes use a laptop, have two tablets and 3-4 phones (don't ask why so many phones!), a rarely used vent fan. The electric blankie uses about 3.5 amps, close to what you mentioned. We don't anticipate an electric bike
On cloudy but warmer days stuck in the camper, I think we use about 25-35 Ah per day... that's a guess. Probably similar for colder days due to heat. We've had to hunker down in bad weather and I'm kinda recalling those numbers. It's really important to know what you use. We'd have to drive after about 3 days stuck inside.
We use a flex panel because I don't want to drill holes in the roof. The aero excuse isn't a very strong one, admittedly. Before we had a 90W suitcase panel that kept up ok, but it was 22 lbs. The 100W flex panel is only 5 lbs and so thin that we put it on the bed when travelling. Not for everybody though because in camp we have to put it on the roof or windshield (or the ground propped against something), tie it down, and reverse the process when breaking camp.
On aero, I'd like to design a fairing but haven't gotten the energy to figure it out. I think it's a tough 3D problem so I'd want to use 3D CFD software. Our windshield is pretty close to the front of the camper, so that aero transition will be tough to solve. I've read about others who've made flat fairings haven't improved gas mileage, but have reduced noise and bug squishes. I'd want to do it right, but too many other projects seem to have priority. But it'd be fun excuse to use my son-in-law's 3D printer. I wish I still had access to 3D modeling, but retired from that stuff a decade ago. However, I
tried 2D modelling a few years ago.
