As Pvstoy points out, capacity is a personal thing according to ones usage...
A LOT of folks on WTW have dc compressor fridges -- so sufficient electrical power isn't a luxury for a lot of us. And it's amazing how much power -- 90 watts -- my laptop charger draws, and if I'm processing photos while still "out there" I need to charge the laptop a lot. Sure, these are my particular needs...but everyone has their particular needs -- which can be greater or less than average.
Sizing the solar capacity for
average use only makes sense to me if the downside of running out of power is negligible.
Yes, you can bring along an extra stand-alone solar panel to deploy if/when needed...but it's simpler to me to just have enough --
plenty of -- capacity on the roof all the time. For me, simpler is better.
And you
could use your truck as a big generator in the campsite...but I'd rather not. Running the engine for a little while appears to do the job because of the transient higher voltage -- the "surface charge" -- that the battery shows for a while after charging stops. You have to run the engine a LONG time to really charge the battery...and gasoline is too expensive and flows too fast through my 6.8L engine! And then there's the noise and smell -- not my preferred camp experience.
I wonder
how much harm -- loss of longevity --
not deep-cycling does to a battery? (
I'm asking because I really don't know.)
That is, if a battery rarely gets below, say, 60% of fully-charged does that reduce its lifetime by 10%? 30%? 50%? Is it different for an AGM vs wet-cell?
If it is a big problem -- if it reduces battery longevity by a lot (whatever "a lot" is), I would use a different approach to making the battery cycle more deeply: Rather than
undersize the solar panels in order to ensure that the battery drains enough when sun is plentiful -- that is, "undersized" from the standpoint of not having enough power in low-sun-angle winter or high-latitude or clouds or tree-cover, why not just
install a simple switch to cut the power from the panels when sun is plentiful and the battery is easily fully charged?
So with an easy way (via a switch) to ensure sufficient deep-cycling while still ensuring worst-case capacity, what's the
downside of a large solar system?
Cost? I spent more on gasoline in one trip to the eastern Sierra than I spent on my entire 240-watt solar system, which will last for
years of trips.
Weight? The panels weigh 45 lb while the camper weighs >1000 lbs and the truck+camper weighs >8000 lb.
Whatever capacity one thinks they need/want, I wouldn't go though FWC for the solar panel system (even if you decide that you want the same capacity they standard-ly provide). You pay a lot more for their installed option compared to doing it yourself. It's not hard to install a solar system -- I did it and I'm not a handyman at all.
That's what works for me, anyway.