OEM Aux Battery Wiring?

[Drifterman]

Good evening all

I'm hoping somebody will be able to point me in the right direction quite easily - I want to connect a leisure battery to my new Renogy DCC50S charger. My initial thought was just to run a fresh cable through to the starter battery in the engine bay, but I've found some cables under the passenger seat that I suspect were originally for the OEM Aux Battery installation. I've trawled the long list of threads (inc @Dellmassive's brilliant 'how I done it' ones), but can't see a setup the same as mine. The crimps are not connected to anything, just insulated in a 'chocbloc' box, but there is a red/blue wire heading back out towards the front of the van.

Having looked at the advice others have had, it looks like the thick red cable should go to the 100A fuse under the starter battery; if that's the case, I plan to just use that for the DCDC charger input. There are no relays and only one 20A fuse in the block going back to the red/blue wire? My guess is that it might go to the dashboard 12v cig lighter socket, but before I pull it apart and get my Fluke out, I just thought I'd ask if the connections look familiar to anybody? Grateful if anybody has an idea...

Here's the cables as I found them under the seat:


Grateful if anybody has any thoughts

 

[Drifterman]

Looks like I just didn't search enough - thanks to the team for merging all the other questions people have posted about the same topic - reckon I'm good now

T6.1 What’s this live feed under my passenger seat? [Merge]

 

[Dellmassive]

Glad your sorted.

That looks like the OEM feed from the main fuse box.

That runs that mini fuse box. And that single fuse may be for the second 12v dash socket?

 

[Drifterman]

Glad your sorted.

That looks like the OEM feed from the main fuse box.

That runs that mini fuse box. And that single fuse may be for the second 12v dash socket?

Thank you @Dellmassive. Yes, checked it tonight - it is the power supply to the top cig lighter socket on the dash

No idea why it has a different supply to the lower one (especially given that both are perm live from the same battery) but at least I know what that wire is for now…

 

[Dellmassive]

That fuse would normally be connected to the second leisure battery so that one socket is from leisure battery and one socket is from starter battery.

 

[Drifterman]

That would make sense, but the two 'original' battery circuits are essentially connected in parallel (via the cable running fro the e-box and 100A fuse), so running that mini fusebox from the terminal on the leisure battery is actually no different to running it straight from the engine battery?

Tbh, it doesn't really matter and I'm ok with both 12v sockets running perm+ from either part of the starter battery power circuit....I don't use them anyway! Any accessories I'll be running will be from the leisure battery I've set up in the back - the only connection between the starter and leisure circuits will be through the DCDC charger

Thanks for taking the time to let me know your thoughts, much appreciated