Solar just won't cut it. Lots of text.

So I made a derp yesterday.  I didn't connect the grounds so the data it was gathering when I went home for lunch was all garbage. I got it fixed, and it was reading reasonably normal.  I don't like the precision of the new meter, but it seemed to be reasonably close to accurate.


I also ran the wire through the current loop sensor backwards resulting in the negative current.  Oops.


As a result, I made new harnesses to properly set this up in the afternoon.


When I got home though, I curiously didn't see what I expected to see.  Not sure what to make of it.


I also did some solar math (here begins the wall of text...).  The short version is that solar alone cannot safely make the trip unless I go solar crazy, supplement the solar, or plan the trip such that I never go more than 2 days without stopping at a campsite.  While all these are doable, they are rather unfortunate.  I need either supplemental charging or forced campsite visits to recharge the battery if I get a few consecutive cloudy days.

I consume 5.5kWh a day, and the battery I am using is 7.5kWh with an 80% depth of discharge, which means I have 6kWh usable.  I could easily double the battery, but that adds another 5k cost and another 200 lbs.

With the 375W panels I can expect each panel to produce 300Wh a day when it is cloudy, taking into account the 20% loss for not being angled and the possible 75% loss on a cloudy day.  If I just roll with 4 of them, that gives me 1.2kWh a day, that means the battery lasts around 32-33 hours.  That is no bueno.  If I do bump it up to 6 panels, then I get ~38-39 hours. Not ideal.   Possibly workable.  If I go solar crazy and find a way to get 8 panels mounted between the truck and the camper, I still only get 46-47 hours, which is doable (I set the threshold at 2 days, and the consumption number is padded), but I am not sure 8 panels is feasible.  If I do a 14' trailer, I could probably do 5 on the camper and 3 on the truck.  5 panels is 16'8" long though, so that means a foot over the front and almost 2 off the back.  Not sure I like that.

With the 310W panels I can expect each panel to produce 248Wh on a cloudy day.  If I find a way to fit all 8 panels (see last post, this is unlikely),  I would get ~40-41h, which isn't terrible.  Possibly workable.

I have also been looking at supplemental DC to DC converters to add 500W of supplemental charging while driving (500W, around 40A off the alternator).  This effectively adds an extra couple of panels and I estimate around 1.6kWh of charge a day that is unaffected by weather.  It isn't entirely clear if this would work (it gets into the whole parallel vs series debate since this would be a parallel system independent of the panels and the panels might drag it down).  I won't need it when it is sunny, so I can unplug it on those days to relieve the strain on the alternator and gas mileage.

If I add a supplemental charger that runs off the alternator while driving, 4 375W panels goes up to ~53 hours.  With 6 375W panels, I get almost 3 days, 68-69 hours.  Basically for a cross country trip if I run into a big batch of inclement weather, I need to have that extra juice, but should be fine as long as I have the truck charger on while driving in inclement weather.  This is probably the only way solar becomes viable (to not use just solar...).  Even in this situation though, I would likely keep a generator as safety.

It isn't clear yet if running something like an inverter generator (supposedly super quiet) is feasible in the back of a truck while parked at a rest stop.  I know semi trucks sometimes idle, and this would be quieter than that (they are about as loud as talking).  If so, than it is an easy win; I wouldn't try a cross country trip without at least a small generator with me anyways.  I could just do 4 375W panels and if I get more than a consecutive day of miserable weather, just turn on the generator.  4 panels on a sunny day (1.2kWh per panel) are almost enough to fully charge the battery every day.  Or just do 5 panels and not care if I go with a 14' trailer instead of a 12'.

If I am going to the trouble of carrying a small portable quiet generator though, then what is the point of solar?  This solar setup is already $10,665 in cost, and is pushing 700lbs (a quarter of the weight rating of the desired trailer) which doesn't include wiring, conduit, panel framing, and so on.  And after all that, I would want a generator for safety anyways given the two day limitations. 

So unless I come across some a-ha moment of clarity with it, I think solar is out.  If the trailer was larger (like Uncle Dennis' 23' trailer) then I would have the space for more panels and spare weight capacity.  I don't want to go that large though, ideally this would be towable by a large car or small SUV.  I will likely get a few cheap 12V batteries and panels and run it like a normal camper, with a generator that I can run in the back in the truck that I will run when I am living/working in the camper.  I can run the lights and water pump and stuff from the 12V battery, pretty much everything but the kitchen appliances and the AC. I just need to make sure I can get a big enough generator (I will need an inverter generator that is something in the 4+kW range).  It will be an expensive generator, but it can back up the house as well and a new generator is on the bucket list anyways.  It removes a ton of weight from the camper too, since I would be down to one or two panels and a small battery.  The only downside to this approach is that it requires a pickup with a cap on it, you obviously can't run it inside an SUV or car.  For the near future though, that won't be issue.