Electrical System

Posted by Bus Conversion

Since electrical power is not (usually) beholden to the forces of gravity or limits of distance, I was able to construct an extensive electrical system without paying much attention to physical layout. I purchased four 12V 220 Ah marine deep cycle batteries from the Interstate outlet in Needham, providing enough electrical storage to conservatively run laptops and lights for around a week. Shop around: I was able to save around $150 with 45 minutes of phone calls.

The batteries would be mounted, very late in the project, in the center of the bus between the frame rails. Two of them would sit behind the (as yet unused as of 4/18/05) drinking water tank, with two in front. Installing the battery connections provied almost impossibly difficult, as the connectors were on top of the batteries with scarce clearance for my hands. After a frustrating session, beset by low blood sugar and cold hands, I nearly electrocuted myself. Be careful with charged batteries. If your leads come into contact with one another, it is likely that they will melt together, causing your battery to rapidly discharge, probably explode, and burn you. I avoided such a fate by grabbing the wires and pulling them apart as hard as I could.

I purchased a set of wires from a specialty battery manufacturer in Boston, but eventually found that Autozone offered much cheaper battery cables. The greatest difficulty arose from trying to attach too many leads to the same battery terminal. For instance, one of the forward batteries would need to accomodate a connection with the other forward battery, the inverter, the new 12V system, and the rear set of batteries. Working a wingnut onto a battery post with 4 leads on it is difficult; more so if you're lying on your back, doing a half sit-up, and can't see what you're doing. Eventually I simply cut and spliced some of the wires together to reduce the number of connections per post.

Our electrical system is not up to code. I believe that it is safe, provided no assumptions about convention are made during future maintenance.

I purchased a Fleetpower/Heartpower (depends on branding...same equipment) 1000W inverter/charger for $250 on eBay and installed it in front of a frame cross-brace, separating the battery compartment from the compartment containing the inverter and a few odd pieces of the air brake system. A slight majority of the web literature favored the purchase of a single unit for power inversion (12V DC --> 110V AC) and charging (110V AC --> 12V DC). Ideally, such a unit should automatically switch over when you plug it in to shore power, and back again when you depart. The inverter I purchased never seemed to charge the batteries, though it would shut itself off to protect its internals. The remote -- a device allowing one to cycle and diagnose the unit -- would have been $125, so I have accepted crawling into the bus 30 or more times during the course of the trip to pop relays, fuses, or simply to switch it on/off/on (the magic combination to get it running again).

It would have been cheaper, and simpler (given the lack of remote) to buy a 2000W inverter for $150 or so, and standard car battery charger. We eventually purchased a charger for $70, and it works reliably. The more expensive class of inverters -- pure sinusoid -- is unnecessary unless you plan on listening to crystal clear music over a 110V stereo. As is, our main cabin stereo buzzes at 60 Hz, since the cheaper inverter outputs a square wave. I can deal: A sinusoid inverter is typically 2-3x the price.

12V wires ran directly from the batteries, bypassing the inverter charger, into a cluster of 12V automotive fuse boxes in the utility wall. 110V lines, from the inverter, ran into a residential-looking circuit breaker panel, also in the utility wall. From the utility wall, wires now run all over the bus. Approximately 15 12V circuits supply the bedrooms, kitchen, desk, cockpit, bathroom, water heater, and fridge. Seven 110V circuits run to outlets scattered along the port side of the bus.

For simplicity, we ran all utilities along the port wall, since there would always be something built to obscure the lines and pipes (with the exception of three electrical conduits running from the desk into the trunk towards the rear of the living room). For the 110V circuits I used standard Romex. I later read in "The Bus Converter's Bible" that one should use stranded wire instead, to reduce the dangers of vibration. I used orange and green 12 gauge stranded wires in the 12V system, since Home Depot was sold out of red at the time.

Most of the longer distance wires run through gray plastic 1" wire conduit. It's cheap, semi-flexible (in case, cough, you mismeasure the hole placement), and can be easily cut to length with a hack saw. Running the wires through the conduit was often a fun challenge. If you plan on packing a ton of wires (more than 3?) per conduit, plan it out to give yourself long runs of access (perhaps taping the wires to a long rigid element to push them through). The Romex yellow shielding particularly was a pain, as it grabbed onto the smoother shielding of the 12V wires and caused them to bunch up. I ended up removing the yellow outer Romex shielding on most of the runs.

Occasionally I used the appropriate junction boxes to terminate wire runs or branch them, but eventually got lazy in many places. If you are comfortable with not meeting either housing or vehicle electrical codes, and are comfortable relying on your experience and "gut feeling" with regards to electrical matters, I think it's ok to be inventive for the sake of saving time or simplifying construction. To wit, the wires running alongside or under water pipes are inside conduit. In other places, the wires are free, zip-tied onto whatever's handy.

I grounded most of the 12V system to the wall-side seat support. I also terminated the main ground wire with a frame bolt. In one later case I noticed that too many 12V circuits were using the same ground connection: Improving the connection improved the performance of the circuits.

Mistakes:

1) With a little more planning or stick-to-itedness I could have constructed a code-happy electrical system.

2) I bargained that after installation, we wouldn't need to mess with the inverter charger or the battery connections. Thus, I did not elect to cut access panels into the floor above those elements to ease access. As Murphy's law dictated, I have crawled under the bus many times. Allow for greater complexity of design or implimentation if it grants you ease of access to your utilities, no matter how trustworthy.

3) I only have one paper copy of "what goes where". Swapping fuses is pretty much guesswork if I can't find it. Do yourself a favor and write a detailed diagram in visible marker on the inside of your utility panel.