Battery
 The first thing to know about RV electrical systems is that as far as your car and your battery are concerned, black is ground and red is hot. But as far as the RV is concerned, black is hot and white is ground. So the black trailer wiring gets connected to the red battery post, and the white trailer wiring gets connected to the black battery post. This gets even more confusing when you throw battery cutoff switches and solar harnesses into the mix. |
The second thing to know about RV electrical systems is that whenever the negative (white trailer wire to cutoff switch, black wire coming out from switch which then goes to black terminal of battery) is connected, the positive (black wire throughout the trailer but red harness with fuse for the last little bit that connects to the red battery post) must be connected. So you will never have the negative connected by itself. This is because if the negative ground is connected and you are messing with the hot wire (such as connecting the solar harness) then anything you touch with it could complete a circuit. ZAP
Another good rule of thumb is that you don't want the trailer plugged in to either the vehicle or shore power whilst doing any of this. And as an added measure of security you'll turn the cutoff switch to off (little red flag) so there can be no ground connection.
The last pearl of wisdom is that the fuse harnesses both connect to the red terminal, whereas there is no fuse on the wire that attaches to the black terminal.
So fundamentally, fuse harnesses get connected to the red terminal first and disconnected last. Simple.
Connecting
- Get a good flashlight and keep it handy
- Ensure you're not hooked up to the vehicle
- Unplug from shore power
- Turn off the battery cutoff switch
- Place the battery in its compartment with the red post towards the centre of the trailer and the black post towards the wall
- Loop the ring connector of the red fuse harness attached to the black trailer wiring over the red battery post
- Loop the ring of the red lead from the otherwise black solar cable fused harness over the red battery post (the other end of the solar harness is negative and is inside the cutoff switch)
- Put a washer over the both of them and then screw down the nut as tight as you can with your fingers
- Connect the black wire from the cutoff switch to the black battery post, followed by a washer, and then tighten it as much as you can by finger
- Check the voltage at the solar quick connect; it should be 12.6 or so volts for a fairly charged battery
- Turn on the cutoff
- The power supply should whine for a second or two and more importantly, the lights should work.
- Plug in the trailer; your voltage at the solar quick connect should jump to 13.5 or thereabouts
- Check for flashing things under the bed; a flashing propane detector will sort itself out after a minute or so
- Get a good flashlight and keep it handy
- Ensure you're not hooked up to the vehicle
- Unplug from shore power
- Turn off the battery cutoff switch
- Disconnect the wire on the black battery post
- Disconnect the wires on the red battery post
- Make sure the washers and nuts are secure on the battery
- Remove the battery and put it on trickle charger
- Tape up the red ring connector, otherwise when the trailer is connected to the car you have a hot wire waving around loose
Battery charge is an oddly complicated subject. The following values are only in any way valid for a disconnected battery that has been at rest for a few hours.
| Charge | Volts |
|---|---|
| 100% | 12.8 |
| 75% | 12.4 |
| 50% | 12 |
| 25% | 11.7 |