Can I connect a Sterling battery maintainer here?

[Itsmcb]

One for the electrical Techies.
I've been searching for the easiest place to fit a battery maintainer in my 1996 swift kontiki without running cables all the way to each battery.
I have a switch on the panel above the sink which selects hab or starter battery as the 12v power source when parked up. (See pic) the cables running to it are quite thick. I assume the following, green/blue feed in from hab battery, green/brown feed in from starter battery, redbrown feed out to 12v control panel. Can I just tap in to the green/blue and green/brown cables to attach the battery maintainer? Also can I then use the adjacent (slightly thinner) lighting cable to attach the maintainer earth/neutral wire? If so, anyone know if the grey wire or the white/orange is the earth/neutral ? Thanks in advance.

 

[Robert Clark]

If it were me I’d connect it across the split charge relay

 

[pappajohn]

If it were me I’d connect it across the split charge relay

At '96 vintage that's going to be under the bonnet attached to the bulkhead next to the battery alongside the fridge relay.... At least my '99 Kontiki was.

 

[Itsmcb]

There's a mess of short inaccessible cables and two relays up next to the battery with no room to work and I'm not sure which wire is which ?. Any reason it won't work where I suggested? I can put the device in the cupboard above.