ELECTRICAL: Roof mounted solar panels to charge a lithium battery bank with enough power to run two mini split air conditioners, a household refrigerator, microwave, and all in one washing machine as well as supply all the DC and AC power needed for all the rest. We’ve got 10kWh of lithium batteries now. They are “rack mount” units of 5kWh each and we are building their rack to allow sliding in a third if real world experience says we need it. Solar panels will be 2500W or more feeding Victron electronics including a MultiPlus inverter/charger/transfer switch able to produce 3000W continuous and 6000W peak.
ELECTRICAL FOR THE GEEKS: We’ll be running a 10.24kWh lithium battery bank consisting of TWO batteries with 5.12kWh. That’s the equivalent of 800ah at 12 volts though ours are 24 volt units. Each battery weighs 101 pounds, has a built in BMS, and a 7000 cycle life before dropping to 80% of capacity. That’s 19.5 YEARS. The RACK holding the batteries will be built to hold THREE with a drawer built into the third slot unless real world conditions indicate a need for another 5kWh of capacity in which case we’ll replace the drawer with another battery. The PV panels will feed the batteries via Victron charge controllers. DC power will be taken off the 24 volt bank and run the length of the bus on one side. That 24 volt line will then feed a 24-12 buck converter which in turn will feed a 12 volt distribution fuse panel. There will be three fuse panels with one in the front, one amidships, and one in the rear. This set up minimizes losses by maintaining the higher 24 volts for the majority of the trip to the point of use as well as minimizing both the length and size of 12 volt circuits. AC power will be generated by a Victron MultiPlus inverter/transfer switch/battery charger capable of 3000W continuous and 6000W peak output. 24 volt battery power will be delivered to a Victron Lynx shunt that will allow monitoring of the system performance. The shunt will attach directly to a Victron Lynx “distributor” and then the MultiPlus. There will also be a Victron Cerbo GX and Cerbo GX Touch so that the performance of the system can be easily monitored. The MultiPlus will then provide power to a 50 amp breaker box from which individual circuits will be run. All AC circuits will be run with metal armored MC cable with stranded conductors.
WATER: 200 gallons of fresh water under the bed to feed the kitchen and bathroom sinks. We’ll start out at each dump and fill with an additional 40-50 gallons of fresh water in a “reclamation” tank for use in the shower, washing machine, two secured outdoor spigots with one on the roof for panel maintenance, and toilet flushing. When used, shower and washing machine water will go to grey tank #1 where it will be processed through a series of filters on it’s way back to the reclamation tank. The kitchen and bathroom sinks with be provided directly from the 200 gallon fresh supply and have tankless hot water using a propane unit and drain to grey tank #2. And after researching toilets of all manner (so called “composting” toilets as well as standard RV, marine, macerating, and both electric and gas incinerating units) we decided we’d prefer to use the black tank and dump facilities method with a nice simple, easy to replace RV toilet. Composting toilets DON’T, macerating units piqued our interest but the potential for a pump, motor, or blades to render us without “facilities” nixed them. Incinerating toilets REALLY piqued our interest but electrics consume over a kilowatt per “flush” and require a liner for each use while gas units were a bit less concerning energy wise but still needed a liner and did consume propane with every flush. Marine toilets, except for the macerating type just didn’t seem to fit the bill and we already covered why we didn’t go with a macerator.
WINDOWS: Our bus has “coach” or “transit” style windows rather than the square ones typically associated with a skoolie. That’s because it was built as a city transit bus and we’re told it began life as a parking lot shuttle for Disneyland before being purchased by a school district in Oregon where it was some sort of activity bus painted in white with team logos and lettering. Anyway, we’ve got sideways sliding windows more like an RV though with no screens. We’ll be deleting all but six of them, two in the front and one in the bedroom on each side. We’ll need the wall space and we want good insulation in the walls.
INSULATION: Speaking of insulation, we’re planing to insulate with 1.5″ of closed cell spray foam on the walls and ceiling. That’s an R-9.75. The roof will also be covered everywhere except a 14″ ceiling vent/fan in the bedroom and a roof access hatch (probably replacing the existing emergency roof hatch) with with solar panels and wood. NOT a deck, just maintenance access (gotta keep those panels clean). There will be an air gap that will serve two purposes, allow relatively cool ambient temperature air under the panels to maintain their efficiency and to shade the roof from solar heating. The floor will be getting closed cell foam insulation 1″ thick with 1/2 ply over that and the finish flooring which hasn’t been decided on. We’d prefer more on the floor but he’s 6’1″ and we have to conserve vertical space. Tanks and storage under the bus will be insulated with foam board as well. Then may be covered by thin plywood and that covered with light galvanized sheet metal for protection from the elements. Outside tanks will all have electric heating pads, flow through air from the interior, or both, that’s still up in the air.
HEATING AND COOLING THE PEOPLE: While underway heating will be provided by the OEM dash heat (supplied by engine coolant “piped” to the front via two 1″ heater hoses and with a helper pump in the engine compartment to help move the hot coolant. We may also reuse the small coolant heater as a mid bus unit to keep the chill off a bit. Of course these only work while driving so we have other heaters as well. The hoses, currently running down the inside of the bus at floor level on the left side will be re routed to underneath the bus to avoid any issues down the road. While stationary, heat will be from two diesel burning “parking heaters” which sip fuel and in a well insulated bus we’ve been told that one will “cook you out”. There will also be backups in the form of a MrHeater propane heater with a line inside the bus and a plain old plug in electric heater. We’d love to put a Cubic Mini or other small solid fuel burning stove in but keep hearing about nightmare issues with insurance companies so we will probably skip that though it would have been perfect for reducing our trash volume on long boondock trips. Air conditioning will also be redundant with two mini splits running on 110-120 AC power from the inverter. A 12,000 BTU unit on the front bulkhead and a 9000 BTU unit in the bedroom.
TANKS: 200 gallons fresh – 40-50 gallons “reclaimed” – 50 gallons each for grey 1 and 2 – and hopefully 120 gallons black. Propane WILL (we already have it on hand, a 29.3 gallon ASME (permanent mount) tank that at the standard (by law) 80% fill will hold 23.5 actual gallons of propane. For comparison, your standard BBQ tank holds 4 gallons at 80% capacity so we’ll have the equivalent of 5.9 BBQ tanks on board AND don’t have to pull them out to get a refill. Of course we also won’t be able to take a tank into town with the Toad and bring it home full but we figure we can live with that.
THE BUS: We already described the bus a bit at least as to it’s construction, history, and type of windows. It’s a 1996 Rear Engine (RE) AmTran which is basically International (Engine and Chassis are International) and was later acquired by International. We bought it from the man who got it from the school with the seats already out. It was a pretty good deal and came with 6 brand new Bridgestone tires, alloy wheels, and automatic snow chains by OnSpot. If you have ever seen big chains hanging underneath a bus and wondered what they were, they’re snow chains. You flip a switch from the drivers seat and air pushes a rubber wheel against the inside of the inside rear wheel causing those chains to spin under the tire whether you’re going forward or back. If yo have a Toad you’ll still have to chain it up but the little tires on a Toad are nothing compared to chaining up those big Bridgestones. We have a DT444T engine which surprisingly is the same engine that powers our 2002 Ford F350 though International made some small changes for the Ford version like an electric fuel pump. The block and basic engine are the same however. That engine is rated for vehicles with a GVWR of up to 75,000 pounds. With our bus limited to 31,800 GVWR and a bring it home weight of 20,450 with a driver in the seat, it shouldn’t have any issues. Especially since we’ve pulled out three complete air conditioning systems each with a large (Transair CM3) and Evaporator (head knocker), plus 200 feet of heavy refrigerant lines and fittings, several hundred feed of 7 wire cables, and three control boards. We’ve also pulled a lot of heavy metal wall off the walls and ceiling that should offset some of the build weight. My F350 on the other hand, having the same engine, can pull a lot more than the owners manual says! The transmission is an Allison 4 speed with lockup torque converter in 3rd and 4th. It’s currently limited to 55mph and the cruise control is disabled but we will be buying the cable to interface with a windows laptop and using the free software from International to change those parameters and perhaps a few others.