Looks good, nice job

Why a 12v batery pack just to energise the relay/solenoid though? You could simply have a suitable fused switch feeding from the 'new' battery to energise the relay and link it with your flat one. Or just fit a simple T-Max controller that will also re-charge your aux once your main battery is up to suitable voltage? FFRR SDV8 Autobiography

Which model Varta did you fit?
Edit - I've spotted the H3.

Probably a silly question but I’ll ask anyway, what’s the purpose of fitting a second battery? Does it make a lot of difference in the day to day running? Just intrigued 2009 (2010 MY) 5.0 Supercharged Autobiography
2007 TDV8 Vogue SE
2005 BMW E63 645ci
2024 Porsche Macan

It helps avoid the dreaded 'low battery - please start engine' warning. and it means you can listen to the radio with the engine off for more than 5 mins

hi james i think i understand what you are explaining . at the moment the second battery is switched on when ing key goes to first position using the green wire in the trailer socket . and it is charging all okay from the alt . so if i take a power live from the second battery in to a switch and then in to the 100 amp relay i can switch it by hand to energise the relay . can i piggy back into the same relay wires 85/86 ing live / and earth new vehicle purchase
2007 supercharged 4.2 java black .sand leather vogue se trim
previous cars .
range rover classic 200 tdi
discovery 1 200 tdi
freelander 2 2008 hse
discovery 1 300 tdi
p38 4.0 ltr man r380 ex royal support vehicle on v5c
discovery td5 man off roader

My aux battery is a deep cycle AGM used to run a fridge that runs even when the engine isn't running, possibly overnight if camping.

I would suggest a Voltage sensing relay to protect the main battery. You can get them that have an override switch and also work both ways ie if you charge the Aux or connect a solar panel once the Aux battery is full the relay switches and the main battery will charge. I would also recommend lifting the loom out of the battery area and securing it above the fusebox, there is enough length. https://www.australiandirect.com.au/Batter...U8QAvD_BwE 2007 TDV8 VSE
2003 TD6 gone.
2002 P38a gone
1999 P38a gone
1997 p38a gone
1993 VSE gone
1992 VSE gone
1966 Series 2a with V8 conversion gone

thanks wayneg for the advice i am waiting for a meter of elec flex tubing to come to wrap the loom to stop it from rubbing thanks oggy new vehicle purchase
2007 supercharged 4.2 java black .sand leather vogue se trim
previous cars .
range rover classic 200 tdi
discovery 1 200 tdi
freelander 2 2008 hse
discovery 1 300 tdi
p38 4.0 ltr man r380 ex royal support vehicle on v5c
discovery td5 man off roader