The conversion of my 86 Crown Supercoach
I reached another milestone with the "new Crown":
I completed the main DC bus and successfully tested it.
Since the main DC bus needed to have six different connections, I built a junction box to accomplish that. I used a 6" x 6" x 4" (1/4" thick plastic box to house everything. I used four terminals for six connections. To construct the terminal block I used machinable plastic. The bus bar is made from two layers of flattened copper tubing.
I placed a battery monitoring module inside the box, along with a hall effect sensor that monitors current flow to/from the batteries.
The expected current flow will reach up to 250 Amps from the alternator and > 250 Amps from the batteries so I used the battery cables from a Crown bus that I parted out years ago (sometimes it pays to keep things). The battery cables connect the second alternator and the batteries to the junction box. The batteries are located in the trunk of the Crown. To provide the best possible negative/ground path for the batteries, I made the connection point to one of the structural elements in the Crown's body, a steel piece that run most of the length of the bus where the sides intersect with the floor. The seats attached to that piece, and the vertical ribs that frame the sides are welded to it. (see image of the cables where thay pass through the floor into the trunk)
The solar is not yet wired up so I wasn't able to test that yet.
The current connections to the bus are:
1. The second alternator.
2. The small inverter. (400 Watts)
3. The large inverter. (3000 Watts)
4. The RV battery charger. (65 Amps)
5. One of two batteries. (deep cycle type 31's)
The cable is run for the output of the bus (lights, etc) but not yet connected to any loads. The cable is run to be connected to the solar charge controller but the charge controller is not yet installed.
To test my work, I connected the battery to the main DC bus with the engine not running, the RV charger off and both inverters off, and the Onan 6.5DKD genset running and on-line through the main electrical panel.
1. I measured the bus voltage at the output terminals of the RV charger and found the expected 12.8 VDC.
2. I applied power to the RV charger and found the voltage increased to about 13.5 VDC.
3. I turned off the RV charger and started the bus engine. The voltage went up to 14.6 VDC at the RV charger connections.
4. I turned on the 400 Watt inverter and it came up but no load was applied.
5. I turned on the 3000 Watt inverter using the push button on its front and it came up. I connected a 5100 lumen LED light to the inverter and it came on.
6. I checked the battery voltage at the battery terminals and verified it matched the reading found at the RV charger.
7. With the Crown's engine running I turned on the RV charger and verified no smoke and found no change in voltage (which I expected).
8. I shut down the Crown's engine and the Onan genset and measured the voltage at the battery terminals and found 12.8 VDC.
9. I setup the meter to measure current flow for parasitic loss. After a momentary surge of current, the current flow stabilized at 17ma.
See attached pictures:
Safety is a major design consideration in how I design the various systems in the bus, so only +12 VDC is present in the junction box, as it is unfused.