Hi all
I want to install a second battery in my 2002 Vogue TD6. Although I have seen several people connect this second battery to the cable at the rear and go through a 140 Amp relay, I have read that a second battery should be connected with a VSR (Voltage Sensitive Relay) using a 25mm² cable from the main battery to the rear where the other one will be.
I would like to read your opinion?
Cheers

I’ve had a second battery installed in the rear for years connected directly to the 100A cable supplying the rear fuse board and a local earth. Never had a problem. I’ve also installed a battery isolator to the front battery.
Switched the front battery off once and then started the car using the rear battery, it just started as normal, the 100A fuse on the rear cable seems to have a bit of tolerance.
Can’t see the point of over complicating the instal.

I have done same as @nicedayforit on both L322 so thats best part of 10 years with no issues only difference is I fitted isolator to rear battery.

Fitted a second battery in the RH boot space, permanently connected to the 100A terminal.
There is a 100A resettable fuse just in case but it has never tripped in five years.
I installed a pair of new Varta AGM batteries to keep things reasonably balanced and topped up by a CTEC charger when not in use.
Simple works fine. Forty years of progress. 1972-2012