newbie solar truck camper setup

Hello solar people, I am new here and so I will start this like so many others have in the past by apologising for my total lack of knowledge about solar, motors, solenoids, watts, volts, amps, awgs, etc etc etc….including my old truck and camper.

I own a 95 ford f250 with a 94 lance camper. It is stored in southern Baja where we boondock 99% of the time. Our electrical needs are small. We need power to charge cameras, laptops, iPads, led lights, water pump, fridge thermostat, control panel, fantastic fan, car stereo, and jacks when arriving and leaving. Needless to say, it is hot and sunny 90% of the time and we need solar (i am sick of listening to the generator which we plan on keeping). 

I looked into buying two 100w solar panels when I was in Baja and was given a quote of 103$ per panel, it seemed very reasonable, so now comes the interesting part of figuring all this out and trying to make it work. I am heading back to Baja in late September and would most likely have to bring everything with me from the US for the set up besides the panels, and maybe a few cables. This makes my planning (and understanding) even more important as I will need all the right parts.

I can order 2 conermex cnx-100 watt panels and have them delivered to Cabo where the camper is stored. I made a nice little schematic of what I am hoping could work. I selected a morningstar ps-30m controller and an xantrex 1000 prowatt inverter, none of which i have purchased yet so if anyone has any reason to think my choices are bad, do not hesitate to let me know.  My schematic says it all. The awgs of the wiring and the wattage of the controller and the breakers might be overkill, but I’m hoping to add another 100w if necessary. I chose breakers over fuses as looking for fuses in Baja might be tough when hours away from civilisation. I am also a true believer in spending more on better equipment the first time around.

I've never done anything like this before so thanks in advance for your patience. I also want to do my best to keep this as simple and maintenance free as possible as everything in Baja is a little complicated. So any advice, suggestions and or opinions in layman’s terms would be much appreciated.

Muchas gracias, Jancsi


  • BB.BB. Super Moderators Posts: 26,768 admin
    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):
    • 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.


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jancsijancsi Registered Users Posts: 5 ✭✭

    Thanks for the in depth and thorough reply to my post! 

    I agree I do not need the 40 breaker but having it near the inverter and controller location will make things easier and quicker in case of some sort of problem or modification. 

    The location I found to be best for the batteries on the old lance is in the outdoor compartment on the right rear where there was a generator that the previous owner got rid of. I would use the little closet under the bench on the inside of camper for controller and inverter, which would be barely 2 feet of cable from battery compartment making a batt sensor irrelevant I believe. I would modify the door of the little closet with some sort of grill for ventilation. 

    I have not looked into car stereos yet. There is the original radio/tape deck still installed in the camper, it’s more a museum piece now and I thought to upgrade it to something with a usb port for mp3 player. I do not have a clue which to chose, if anyone has a proposal for a stereo (does not need to be loud), please let me know.

    I mostly need an inverter to charge cameras and laptop, but I was thinking of getting a small air compressor to fill tires when not driving on sand in Baja. I have not bought the compressor yet but maybe there is one that can work with the Morningstar 300w inv. I will have to study them. I do like the inv. you proposed and think i will most likely choose that one.

    Now to the solar array…I think we will start by adapting ourselves to the array (2 x 100w) as opposed to adapting the array to our needs. There is space for one more panel, but I would rather try to avoid the added weight for now although it is very tempting to go bigger. There is no real space for more batteries and the weight of those is impressive. Our loads are pretty minimal, and charging of cameras, laptops and iPads could be done after full batt. charge during the brightest part of the day. Same with the fantastic fan, it really is only needed during the daytime as evenings tend to be cooler temps. Evening loads would be a couple led lights and the Lance appliances (gas fridge lights and panel, control panel lights, gas leak detector). As we live with the sun we are never late to bed.

    So, with what I have drawn up, adding a third panel should not be a problem? The wire awgs and breakers would not need to be modified? It would be perfect if adding a third panel would mean just opening the rooftop connector box and connecting two wires.

    Thanks again for your time.

  • BB.BB. Super Moderators Posts: 26,768 admin
    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.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jancsijancsi Registered Users Posts: 5 ✭✭
    ok that is what i was hoping was the case. I will look at compressors more closely, its hard to find much information on how much power they need. On another subject, how does the ground work on an isolated truck camper? I saw the house batt. was grounded to the frame of the camper, and figured i would do something similar at the new location where the two 6v will be stored. What about grounding for the inverter and the controller, would this be done at the same location? How is it that grounding actually works on a rubber tired RV?  I also have a question about the prostar ps30-m. Does the lcd screen give the same information as having a trimetric 2025v? Or does the trimetric offer more information about the state of the battery and its charge? And lastly, would using the prostar ps-30 without screen and the trimetric make most sense?
  • BB.BB. Super Moderators Posts: 26,768 admin
    edited June 2016 #6
    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 B) 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.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 Solar Expert Posts: 613 ✭✭✭✭
    If you want a 12v compressor that will last look at Gast or ARB.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • jancsijancsi Registered Users Posts: 5 ✭✭
    I have bought the morningstar sure sine 300w inverter. It will just have one outlet coming from it in order to charge camera's, drill batteries, laptops and have a fan running. Do I have to ground the inverter on the frame of the truck camper? Instructions call for 4awg, I have 4awg already coming from + - of 2 6v golf cart batteries to power the inverter. Do I need a fuse on the outlet? The outlet is a voltech GFCI, a double grounded receptacle. thanks, again, Jancsi
  • BB.BB. Super Moderators Posts: 26,768 admin
    If the inverter is bolted to a grounded/metal frame of the camper, not really. If it is bolted to plywood in a closet (hopefully, with good ventilation), then it would be a good idea. The ground is there if there is a short inside the inverter to the metal case--The ground connection will pop the fuse/breaker in the + line to inverter' input.

    No--I do not believe you need any fuses/breakers in the AC output of that 300 Watt AC inverter as long as you are using 14 AWG wiring... If you are using much smaller awg, then perhaps yes.

    You do not really need a GFI output if the inverter's AC output is floating (no Neutral/white wire to chassis ground). Floating transformer outputs do not need GFI as touching the "hot lead" to ground will not cause current flow. As long as you do not have any false tripping of the GFI--It does not hurt.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jancsijancsi Registered Users Posts: 5 ✭✭
    Ok, interesting. The inverter is mounted on plywood inside small closet with no door at all. On AC side only one outlet (although I have another outlet with both 110 and 2 usb ports that I would like to use as well, would this be safe?) I have 12 awg wires as well to connect outlets. No need to fuse the outlets?  Now just to get the ground situation correct: I have what seems like an easy option to run a 4awg cable and connect it to the casing that is essentially the sidewall of the generator compartment (where i have installed the 2 6v batt.) I could drill a hole and bolt it there, about 1.5 ft distance. Would this be considered a ground? cheers, j
  • BB.BB. Super Moderators Posts: 26,768 admin
    The 300 Watt Morningstar TSW inverter is good for ~600 watts for 10 minutes or so:
    • 600 Watts / 115 volts = 5.2 Amps AC rated current (surge current at that)
    12 AWG wiring is generally good for 20 Amps (NEC) so--Putting a 15-20 amp breaker/fuse on the AC output of the Morningstar inverter will never trip.

    The other "issue" to neutral bond the "white wire" from the inverter. The Morningstar is a TSW (true sine wave) inverter with a transformer isolated output. If you want to "copy" the NEC, you would tie one AC output from the inverter to chassis ground--That becomes your "white/neutral" wire. If you had florescent tube fixtures, 120 VAC spark ignitors for a stove, and such--A grounded neutral makes those more reliable (starting the florescent, detecting flame for the ignitor). If you have screw type bulbs (120 volt Edison base normal USA bulbs), the socket base is supposed to be tied to neutral to reduce the chance of shock.

    But--It is purely your choice--On average, you will not see any difference how things operate and will be still safe (checking voltage from AC lines to ground will be wonky--If you do not have the inverter's AC output neutral tied to ground).

    You want the "ground" to be heavy enough to pop your fuse/breaker for the 300 Watt inverter:
    • 600 Watts * 1/10.5 volts cutoff * 1/0.85 inverter eff * 1.25 NEC derating for wiring/breakers = 84 Amp minimum branch circuit rating (round up to next standard wiring/fuse/breaker).
    I don't know how heavy the sheet-metal in the RV is, and such... Generally, a ground lug connection with Battery negative connected to sheet metal, and your 4 AWG from the inverter chassis to that same connection point is "ideal". Yes--It is overkill, but what is recommended for safety. You could us 6 AWG from the inverter case to the common chassis/battery ground too (6 awg is heavy enough the pop the fuse/breaker for the DC inverter's + input).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonathanginojonathangino Registered Users Posts: 4
    mosfet stereo amps use very little power.  if you just run off a mosfet head unit, it will draw virtually nothing, even at full volume.  
  • EstragonEstragon Registered Users Posts: 1,433 ✭✭✭✭
    Might have missed it, but does the camper have a shore power connection?
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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