Trailer mounted systems?

Badfish740Badfish740 Registered Users Posts: 13
I'm currently evaluating the possibility of purchasing a hybrid with the intention of setting it up for use as an emergency generator at my home, and a standalone power source at a planned off-grid cabin. The easy portability and multiple functionality of a vehicle and generator (with built in battery storage) is very appealing, but I think back to how I arrived at this idea. What I had initially thought of was mounting a generator, battery bank, and inverter on a trailer. This way I could easily use the generator on an emergency basis at my home via a transfer switch, and also tow it behind my vehicle on trips to the off-grid property where it would be directly connected to the main panel.

I've seen a lot of posts about off-grid systems built into travel trailers, but nothing about a more compact "power pack" type of system sized to fit on a 5x8 or so trailer. Does anyone have pictures of a such a system they've ever seen or built? I'm just trying to get some ideas at this point. It could be configured in a number of ways-propane would be the fuel of choice. A 5x8 trailer could easily accommodate four 40lb cylinders side by side which would weigh about 300lbs by the time all of the plumbing, added-add in another 300lbs for the generator itself. Even limiting myself to 75% of my actual towing capacity, I still can handle a gross trailer weight of 3750lbs, so if the generator and fuel only take up about 600lbs, and the trailer itself weighs in at 1000lbs (probably a little less), that still leaves me with about a ton for batteries and 150lbs for miscellaneous other stuff.

Here are the loads I'd be looking to power in both places:

Home emergency use
Standard size refrigerator
100CF chest freezer
Two .25HP Sump pumps
800CFM Furnace blower (Wood burning furnace, so no other electrical components to operate)
4800W water heater element (Cycled, obviously)
LED TV/satellite box
Chargers for laptop, tablet, cell phones, etc...
Modem and wireless router
Note: We have city water and sewer so no well or septic mound pump to operate

Off grid cabin use
Deep well pump
Propane refrigerator
All LED lighting
LED TV/satellite box
Modem/router/laptop/cell phone charging

My home needs are more extensive than the cabin needs by far, but that is fine since it will mean that the generator will run a lot less when we are there. I also don't know how solar (Also mounted on the trailer) would factor into this or whether or not it would be worth incorporating. I will say that I'd be much more inclined to mount solar panels on a trailer than to leave them at the cabin (or the generator, batteries, and inverter for that matter). I'll be interested to hear thoughts from others who have either contemplated or tackled a similar project.


  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: Trailer mounted systems?

    This is from awhile back, and I didn't do it, Toyota did. "The Long Ranger."

    It used a 500cc motorcycle engine as the generator, and was supposed to be pretty efficient.
  • BB.BB. Super Moderators, Administrators Posts: 30,037 admin
    Re: Trailer mounted systems?

    As you have asked the question--You are looking at a 5-10 kWatt genset that will burn a minimum of 0.5 to 1 gallon of fuel per hour.

    There are two major design issues with electrical power... The peak wattage which defines the minimum size of the genset, AC inverter, etc. The deep well pump may be a 1-1.5 HP electric motor, and the 4.8 kWatt electric water heater are two killers here.

    And then there is the average power per day (Watt*Hours or kWH per day) that you need to supply. That is, more or less, your fuel supply and size of the battery bank (voltage and Amp*Hour capacity). For your cabin, other than the well pump, you do not have much energy needs per day. For your home, the water heater, refrigerator+freezer and such are the primary power usage--But computer systems can also be very significant loads too.

    And then there are solar panels... You need a relatively large number of panels to supply relatively large amounts of electrical energy. The sun only supplies power 4-6 hours per day--So you need a large battery bank to charge during the day, and then supply power when the sun is down.

    When it comes down to money... Off grid power usually costs in the range of $1 to $2+ per kWH (solar, generator, etc.). That is about 10x the amount you would pay your local utility (in the $0.10 to $0.30 per kWH for most people in the US).

    For a generator--Paying 10x the cost for a few days of emergency backup power--Is not going to kill you. However, if you are looking at weeks to months of power usage (major storm damage, off grid home/cabin), the costs to support a "standard North American Home" of ~1,000 kWH per month would be around $10,000 per month power bill.

    Generators are (relatively) cheap--So you pay a few thousand dollars for the genset, and pay for fuel as you use it (and if not natural gas, but gasoline/diesel/propane, when you buy fuel for storage). And fuel is the killer (both storage, most fuel goes bad in storage--Propane being the exception, and natural gas from the utility is always "fresh"--assuming you have/keep natural gas during storms).

    For solar electric power--You pay a much of the costs for the parts and installation (i.e., pay 5-10 years of electrical bills "up front"), and maintenance--Batteries last 3-5-8 years or so, and electronics last ~10+ years plus the occasional failure. Solar power rarely makes sense as a pure emergency backup power system except for relatively small systems (~1kWH per day or ~100 kWH per month would be my suggested "maximum" backup/part time system design goal for a pure backup system). But that would require you to be "happy" with 1/100'th of the amount of energy you probably use in your home during normal times (no electric hot water, no refrigerator, no freezer, no well pump, etc.).

    So--The first step for most of us is to "know your loads", then lots of conservation, and finally, looking at generator+fuel for short term outages (less than ~2 weeks). And possibly at solar+batteries for longer term outages (months) and cabin usage.

    Other than a generator+fuel on a trailer--Portable solar is difficult to justify. Batteries are heavy and solar panels are large--Plus you need a good structure for the solar array--You don't want to solar panels to get broken during travel or blown off the trailer during travel/by wind storms.

    Comparing a typical north American home of 1,000 kWH per month electrical usage or ~33 kWH per day:
    • 0.33 WH per day (330 WH per day) == Lights, cell phone charger, small water pump, a little laptop use
    • 1 kWH (1,000 WH) per day == Lights+Radio+LED TV+Laptop+Cell phone charging+small Water pump (assuming you are very careful power power usage)
    • 3.3 kWH per day == Add a fulls size energy star refrigerator + well pump (may need new "solar friendly" pump in well) + clothes washer
    • 10 kW per day == Add some electrical cooking (microwave, toaster oven, central heat, etc.)--A very efficient home and "near normal" electrical life
    • 33 kWH per day == Normal north American home (electric water heater, some A/C)
    • 100 kWH per day == Air conditioning for Florida/Texas, irrigation water, etc.
    So--Start with your loads and needs... And conservation. Then decide if your emergency power needs are more towards a full time off grid home, or more like short term camping.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Trailer mounted systems?

    Here is my generator.
    When I bought it for $100 it had bad brushes, dead starting battery and busted wheels. A local construction company abused this machine for 3 years running electric jack hammers and such off it. When they killed it I guess they figured they had gotten their $1000 they originally paid for it out of it and put it up for sale for some sucker to buy (me).

    I built a frame for it specifically for high mobility, to go on and be secured to a trailer.
    As you can see in the pictures I put heavy duty wheels on this additional frame, these wheels support the load of the generator, extra fuel, cord sets, go over uneven ground and clamping load from being cargo strapped to a trailer. They can be pushed up a trailer ramp too.
    If you look at the base of the frame you can see I welded chain half links to the frame, this allows me to cargo strap it or lock it down so some one cant make off with it so easy. Look closely in one picture and you can see a lock locking the trailer to a chain.
    In another picture I added 3/8 inch lifting eyes so that it can be lifted by hoist and set in the back of a trailer or pickup.
    Then to keep all the dust and rain off it I cover it with a $9 lowes construction demolition bag.

    This is not a generator that you want to run every day. Its rated to suck 0.77 gallons of fuel per hour at half load.
    Because of this catastrophic fuel consumption I added an additional 5 gallon fuel tank, a space to hold another 5 gallon gas can (for storage and transport only) in addition to its 8 gallon OEM fuel tank and added a 1000w pure sine wave power invert to its over sized optima AGM battery.

    The added inverter is the best mod by far it saves a ton of fuel and keeps a lot of hours off the generator.

    So if you are looking for a generator to move around a lot, expect the wheels to fall off rather quickly. I do no recommend just setting something big like a generator in the back of your trailer or truck and assuming gravity will always hold it in place you need to strap it down with chain and or cargo strap. If you want a generator that will not have its legs fall off or wheels break off quickly, you are not going to find one for a reasonable amount of money. I would recommend doing something like I did.

    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.

  • mike95490mike95490 Solar Expert Posts: 8,606 ✭✭✭✭✭
    Re: Trailer mounted systems?

    That's a lot of loads. You might make a "fancy" system with a auto-throttle inverter genset, with a high end, off-grid inverter with generator support for peak surges.
    (generator support means the inverter, at periods of high loads, stops charging batteries, and switches to invert mode, to assist the generator loads), A 6Kw inverter with a 3Kw generator can handle 9Kw of peak load. As batteries approach full, the charger eases off the amps, and the auto-throttle slows the generator down, saving fuel and noise.

    BUT you first need to convert
    Home emergency use
    Standard size refrigerator
    100CF chest freezer
    Two .25HP Sump pumps
    _to_ watt hours
    Fridge: 2.2Kwh
    freezer .8Kwh
    sump pumps 14.5Kwh (bad weather, running 24/7, 300w each ?)
    Whoa - those loads add up fast.
    That's what the batteries, inverter and generator have to support.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

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