I have just purchased a cigarette lighter adapter (https://www.ebay.com.au/itm/12V-2-Ports ... 2749.l2649), and need to wire it directly to the battery in my caravan (no more than 50cm from battery to adapter). I am not sure exactly how to do this, but I have sketched two possible wiring solutions (attached). I may also add a switch and fuse between the battery and adapter.
Would single core 6mm (not 6mm sq.) wire be sufficient, as well as a 10A fuse?
Technically both diagrams show the circuits in parallel. The +ve wire has the same voltage at each adapter and each will operate independently. The big difference is that in diag 3 the current in the wiring will be higher if more than one outlet is used at a time as all 3 units will draw power through one wire. This is not an issue so long as the wire is heavy enough to carry the expected full load of the circuit. Diag 2 would only require 1 fuse but it would need to be rated higher that the 3 fuses required in diag 1. This may cause a problem in that if one outlet is being used and develops a fault, the fuse may be to big to blow. Only way to determine the size of fuses and wiring required is to have a look at what you will be running of each, the current the draw, how many outlets are likely to be used at the same time and the size of the wire can then be calculated taking into account the distance from the battery to the adapter.
Please do not use the clip locks shown in the eBay ad to connect into the van wiring. Experience has shown those connectors to be dodgy at the best of times.
Iza
__________________
Iza
Semi-permanent state of being Recreationally Outraged as a defence against boredom during lockdown.
Just *(almost) finished wiring a similar set up in my van.
Used a variation of the top diagram.
I ran the largest wire that I had lying about I think 8 or 12 awg but via a fuse in my 12V fuse box and most importantly a switch. I just paralled up the sockets with quick connect terminals & connected the battery & earth to the top terminals.
My set up has a twin USB , normal auto 12v socket & a Merit socket.
I found that the USB outlet had a permanent current drain so I included the switch to get rid of that when not in use. Why waste precious battery power? The switch went into the common feed for simplicity. (Rather than just in the USB battery lead - although I could easily change that if I want).
As well as a SOC set up inside the 12V cupboard, I put in a digital Voltmeter (like yours) adjacent to the 12v outlets, that is wired directly from the battery (of course through a fuse). I can see the terminal voltage as I walk in the van door, which is convenient.
* note. I am almost finished because I am still waiting, only been 2 months, for a $7 set of switches that are on a slow boat from China. A couple of months wait to save a few dollars. Never again.