newbie solar truck camper setup

Welcome to the forum Jancsi.

Your basics look fine... You don't need the 40 breaker in the solar panel wiring--However, it will not hurt and is nice so you can turn on/off the panels if you ever want to (such as resetting the charge controller--If the two breakers for the solar panels are difficult to reach--And for two panels, you really do not even need those breakers either--Only need per panel breakers if you have ~3 or more panels in parallel).

Breakers are usually a very good solution vs fuses+switches... With larger fuses and holders, blow one fuse and you have now paid for a breaker (and, carrying spares = costs+storage+trying to find when needed).

In an area with wildly swinging temperatures (day/night)--You a) want the solar charge controller to be (roughly) at the same temperature of the batteries, but not getting acid mist from battery charging on controller; or b) you want to get a solar charge controller with a remote temperature sensor option (to measure the battery temperatures directly).

However, before we go picking components--I want to review your energy usage and expectations.

First, conservation--I think you have that pretty well nailed--Except I would look at the car stereo--In decades past, many car stereos where not very energy efficient. Depending on details and how high you crank the volume.

Also, I would suggest that a 1,000 Watt inverter may be over sized for the capability of your present battery+panel design (unless you have high power/short term power needs like a power tool or similar).

Since you have not told me about your power usage (watts average, peak watts, Watts*Hours of use per day, or similar in Amp*Hours)--I will base the math on your battery bank size. And see what works out for the rest of the design (I assume that more solar panels will fit on your RV--If needed).

First, how much power (watts) and energy (watt*hours) from your battery bank. Assuming 6 volt * 200 AH "golf cart" batteries, 2x series for 12 volt @ 200 AH battery bank. Assume all energy is from AC inverter (~85% efficient--Conservative estimates--Golf Cart batteries are usually a very good choice for low cost/reasonably rugged/reliable/forgiving).

• 12 volts * 200 AH * 0.50 maximum discharge (longer battery life) * 0.85 AC inverter eff = 1,020 Watt*Hour of storage
  
• 12 volts * 200 AH * 0.50 maximum discharge (longer battery life) * 0.85 AC inverter eff * 1/20 hour discharge rate = 51 Watt average load (5 hours per night, two nights, to 50% maximum discharge)
• 12 volts * 200 AH * 0.50 maximum discharge (longer battery life) * 0.85 AC inverter eff * 1/8 hour discharge rate =127.5 Watts max continuous load (4 hours to 50% maximum discharge)
• 12 volts * 200 AH * 0.50 maximum discharge (longer battery life) * 0.85 AC inverter eff * 1/5 hour discharge rate =255 Watt suggested maximum discharge rate (minutes to an hour or so)
• 12 volts * 200 AH * 0.50 maximum discharge (longer battery life) * 0.85 AC inverter eff * 1/2.5 hour discharge rate =510 Watt maximum surge (seconds to minutes)
  

So--My suggestion for this size battery bank would be a MorningStar 300 Watt TSW 12 volt inverter (the Xantrex is fine, just too big to be useful). The MorningStar also has remote on/off and "search mode".

Note the above are based on the battery's 20 Hour discharge rate... As you discharge at higher current levels, the "aparent capacity" does go down--So take the above numbers as "rough estimates"--Not exact guarantees (in solar power, rough estimates are usally "close enough" for our needs).

A 1,020 Watt*Hour in AC power (or 200 AH * 0.50 max discharge = 100 AH "useful capacity" @ 12 volts) is a good size system for a small cabin/RV running lights and electronics (with lots of conservation). But you must be careful with energy usage.

Next, two ways of calculating the size of your solar array... First is based on battery bank capacity--Second is based on energy used per day. For battery capacity, we suggest 5% to 13% rate of charge with solar works well (charge during day, use power at night). 5% is the minimum for we suggest for weekend/seasonal usage. 10% or more for full time off grid. You can use >13% if you use a lot of energy during the day too (running computer, internet, printer, work lights, etc. and still want your battery stored power during the day).

• 200 AH * 14.5 volts charging * 1/0.77 panel+charger deratings * 0.05 rate of charge = 188 Watt array minimum
  
• 200 AH * 14.5 volts charging * 1/0.77 panel+charger deratings * 0.10 rate of charge = 377 Watt array nominal
  
• 200 AH * 14.5 volts charging * 1/0.77 panel+charger deratings * 0.13 rate of charge = 490 Watt array "cost effective" maximum
  

Your 200 Watt array is near minimum--But since you are in Baja with lots of sun--It may do OK for you--As long as you watch your energy usage--I.e., don't use power during the day until the battery bank is charged (you really need 5% to 10% minimum current to properly recharge the battery bank). If most of your loads are night time (charge daytime, use battery at night), then your 200 Watt array can work.

Next, solar array based on your loads... You can use this link to find a city near where you operate (or some other source) to give you "hours per day of sun"... For now, assume 5 hours per day minimum (on average for 120 VAC power):
http://solarelectricityhandbook.com/solar-irradiance.html

• 200 Watt array * 0.52 typical AC system eff * 5.0 hours of sun = 520 WH per day (minimum average)
  
• 377 Watt array * 0.52 typical AC system eff * 5.0 hours of sun = 980 WH per day
  
• 490 Watt array * 0.52 typical AC system eff * 5.0 hours of sun = 1,274 WH per day
  

If you do not use a lot of power (1/4 of battery capacity per day or ~500 WH), then the 200 Watt array will do OK most of the time.

If you use a lot more energy (computer, electronics, fans, etc.) during daytime too--Then I would suggest you would be happier with more solar panels.

Of course, you can backup excess power use with the genset--But given the "cheap" prices for solar panels these days--I would be suggesting more solar than 200 Watts of solar.

Thoughts?

-Bill

Everything looks fine otherwise... Yes, you should be able to add the third panel without needing to change the existing 8 awg wire run to a heavier cable.

There are those "emergency" DC air compressors for cars--But, as always, those probably will not last that long if you use it a lot. Finding an AC compressor to run on the small (or even 1,000 watt) AC inverter--That will not be easy.

I guess many of the DC air compressors take upwards of 14.5 amps--And most automotive DC cigarette outlets are fused at 10 amps... For reliability, having some extra fuses and/or wiring up a new lighter outlet with heavy duty wiring or replacing with dedicated high current connectors.

-Bill

1. DC compressors--Should be designed for ~10 amps maximum (fuse rating for US lighter sockets--typically). If you have heavier wiring+larger breaker+better connectors, less voltage drop on wiring, so DC pump will probably draw even a bit more current--Should be fine. AC compressors, probably difficult to find a 300 Watt "inexpensive" commercial compressor (suggest use DC and see how long it lasts for your usage).
2. Grounding--Two major grounding types: A) electrical grounding. Camper frame/sheet-metal/plumbing/etc. all tied to Battery negative ground. If Hot lead touches metal, pops fuse/breaker (small AC systems with TSW inverters can usually be grounded for neutral lead or left floating--pluses and minuses for both ways--leaving AC floating common on smaller inverters/gensets). And lightning grounding--All metal/DC grounds (and even AC Neutral Grounded for most TSW inverters)--Can reduce "lightning" inside the RV and electrical damage--RV grounding to earth--4 inches of "rubber" are not going to stop a lightning strike that went 2 miles through air. In dry climates, drag chain (or similar) discharges static build up and stops small static shocks for people climbing in RV. If you are in lightning area, a ground stake or buried ground plate (for fixed/longer term installations) could be a bit safer for lightning prone areas (don't be outside if you heart thunder/see lightning--Inside metal shell is safest). Direct strike, not much really helps. Lots of conversation about grounding, if you want.
   
3. For many Solar Controller Companies, the options (displays, remote battery temp sensors) are clearly "high profit" items. Some systems use the display to further program the controllers (charge controller, AC inverter, Chargers, etc.). Look at the function(s) display offers. Having voltage/current/status can be helpful--But may not be worth the money to you. Some items need program-ability (like Outback products) for optimal operation. State of charge, few charge controller offer better than rough estimates. You can purchase true Battery Monitors (or integrated monitors for a few charge controllers) that are more accurate (note, even "good battery monitors" have their limitations too). Again, more talking--if you are interested.
4. I do not sell/use these products--So I cannot really tell you if the LCD Meter+ProStar is useful or not. A Trimetric battery monitor can be a big help (especially if you use AGM/Sealed batteries).
   

Any one of the above questions are worthy of additional/full discussion(s) by themselves.

-Bill