Split charge and jumping yourself off

If just fitted a durite split charge relay in the disco using 25mm cable . Prob over kill but was needed if my other idea will work.
I plan to use a remote starter solenoid to bridge the split charge . If ever main batt is flat to jump myself off.
I plan to energise it incar .so if main is flat the solenoid will bridge the batts so i can start engine . then switch off solenoid so then the split charge relay is back in service as normal .

Is there any thing wrong in this idea

Nope.

Nothing apart from 25mm2 is a bit feeble.

I've fitted twin Anderson plugs connected to each battery by 54mm2 cable. It's bridged by an isolater switch.

The old Lucas type starter solenoid at around 12 quid was what I had in mind for this same job.......only another 6 quid over the manual option

Thats what i was thinking

Sounds just fine. I'm only using AWG 4 for split charge and AWG 2 for winch and starter and has been all good.

I only use a 120A relay (in fact my split charge circuits are fused at 100A) but if I wanted to self jump I would just allow main battery to charge starter battery for a while.

That said, my setup is slightly different, because driver side (original) battery supplies starter motor, ECU (injectors and coil packs) and fuel pump, and then my secondary battery supplies all the auxiliary circuits.

I only need enough power in second battery to switch a relay and energise the starter solenoid to start the car, which works quite nicely when camping etc cos the car can be drained right down!