So I've identified a zone in the middle of the house that could do with an off-grid battery backup. The zone is served by four 13A radials that run back to a services cupboard (adjacent to an airing cupboard) that was originally used for a home-brew DMX lighting setup I built over 20 years ago. The idea is to install a modest 24V 100AH LFP battery and Victron 800W Multiplus intverter/charger in there. The zone has around 300W of 'essential' appliances: Sky Q, Oled TV, HT Amp, Broadband router an