And more finishing touches at the electrics

In principle all the wiring had been completed, but two things needed to be done: the internal lighting of the switch for the external 12V supply needed to be connected, and the ampmeter for the internal consumers needed to be properly wired so that it also would show current when the power supply was used instead of the solar/leisure battery circuits.

The switch does connect the POWER-ON line with the GROUND from the power supply. I decided to use the -12V as the other connector for the switch illumination, so that the direction of the current is the same as originally intended in this switch (there is ACC, power, and ground connection at the switch, and since ACC and power are already on ground level, the remaining connection should not be +12V; this is important if the illuminator is an LED, where the direction of the current matters).

The ampmeter just needed some rewiring of the common ground return cable, which I had connected to the common terminal block instead of going through the ampmeter resistor first. I changed this, and now the meter also shows the current when the consumers in the car are connected to the 12V power supply instead of the leisure battery.

The cabling looks chaotic, but is all well-thought-through :) :

Once the cabling is hidden and the big wiring board is moved and affixed into its position, it looks more tidy. Even the coffee machine is back in place:

A heavy-duty electric socket/plug

For working on the electrics I have to take that board with all the switches and cables out of the car. It has been easy to remove - just one screw at the top, and I could take the board out and work on improving the electrics. But everytime I took the board out, I also had to unscrew several electric connections: vehicle ground, vehicle battery, leisure +/-, solar panel +/-, lamps. The cables are not getting better from often removing them form the screw-terminals, so I was considering to use plugs instead. I found several connectors at Maplin which were suitable for the lighting connections (ok for 6A) and the solar panel connection (20A is sufficient, as I have seen never more than 6A coming from the solar panel). But I was not able to find a suitable socket and plug for the battery: I have designed everything to be able to support at least 30A (solar controller, thick cables, circuit breakers). Therefore I was looking on ebay, and I found one, shipped directly from China: a heavy duty connector with four pins, used foe 380V and permitting 30A.

This connector is also waterproof. So I connected the leads from the two batteries into the socket, and connected the plug to the board.

Now it takes much shorter to get the board out: simply unplug all the connectors, remove the one tightening screw, and the board can be removed.

And while at it, I also added a cover board to hide the cabling out of the view. And improved the attachment of the board: now with two screws (one at the bottom onto the work surface, the other on the top onto the shelf.

Upgrade of the 12V electrics

When preparing the vertical auxiliary panel, I used the opportunity to re-wire the electric box which I had assembled. It had been too small to be closed, so I now used all that empty space in between the panels for laying out the wiring more generously, with better access. I also had bought a new volt/amp meter for the battery which would indicate if current goes into the battery (charging) or goes out. The previously used ampmeter only did show current that did come out of the battery. The new meter is installed in the grey box in the centre. I will still have to decide what to do with the now obsolete previous V/A meter.

I also got another solar controller, rated at 30A, which has a multifunction display and shows more information about the status of the voltages / currents. And I added two green LEDs which indicate the status of the split charge relay: one LED indicates it there is voltage from the front vehicle battery arriving at the split charge relay, and the other LED indicates if the split charge relay is connecting both batteries (when the engine is on and the alternator recharges both batteries).

Electrics - control box

For white a while I had all the electric wiring for the solar controller and the refrigerator done with flying wires, without any hidden installation. I had added a split charge relay, and had connected this to another relay to disconnect the solar panel when the engine alternator was charging the leisure battery. Worked all fine, but did not look very good.

For quite a while I had designed a control box which I wanted to place in between all my electrics and the solar control box. My own box would provide me with voltages and currents, so I could finally see how much the solar panel would charge the battery, and how much my electrics would use. Here is the latest plan of this concept:

From left to right the solar controller basically has 6 inputs: +/- from solar panel, +/- from/to leisure battery, and +/- to electric load. My own box would have the same 6 inputs, would then do some switching and voltage/current measurement, then have the 6 outputs which would then connect to the solar controller. In addition I planned to connect the vehicle battery/alternator for charging while driving, then an external 12V source in case I have external power, and an input for an external battery charger. The above schematics allows all this: automatic switching to external 12V, when such a source is connected; manual choice of charging the battery; integrated split charge relay for automatic switching to charging from vehicle while engine is on; automatic disconnect of the solar panel while driving; manual override of split charge relay for explicit linking of the batteries even when not driving (for example for charging both the leisure and the car battery from the solar panel). And the design allows to show the voltages and currents in the three circuits: the solar panel, the leisure battery, and the connected load. Furthermore I wanted an external high-current output, bypassing all controllers in case I connect a high-powered device (e.g. a microwave oven).

Over the time I had bought all the necessary components: 3 Volt/Ampmeters, relays, wires, and a suitable box.

So I began to build. First added a little board inside the box, so I could mount the components onto it. Here is the volt/ampmeter with the required shunt resistor (a low ohm resistor which is used to measure a voltage across, which is then interpreted as a current).

I tried various layouts of the backplane in the box:

The front plane would have three data displays plus two switches: one for switching on the external battery charging, another one for bridging the split charge relay.

Then everything would come together...

... and I realised that the box was too small. The thick wires (for up to 40 Ampere) and the bulky terminals did not leave any wiggle room. While in theory all the relays and the (overly large) shunt resistors would fit, in practise I was not able to close the box without the risk of creating a short circuit somewhere or damaging those very fine and sensitive Volt/Ampmenter wires. So I decided to leave the box open for now and connect it to the vehicle anyway. At the front there is now also a switchable circuit breaker for the electric consumer loads.

And - it works! The above picture shows the voltages and currents as the solar panel is loading (left v/a meter), the battery provides some output current as well (center v/a meter), and the refrigerator is on and drawing current (right v/a meter). So for the first time I can see what is actually going on in the circuits . great! Theoretically the currents of the solar panel and the battery should add up to the load - but they are 200 mA short; not sure why that is... possibly the solar panel controller uses a bit of power (each of the v/a meters uses 20 mA) ... but it also could be because the controller regulates current and voltage in the battery and in the load circuits, so that it is not the current that should add up, but the power. Based on this, there is a leakage of around 400 mW.

Now I can temporarily mount this box on the vertical panel and have finally a more empty work top. The external wiring is not yet final and will be shortened eventually.