Originally Posted by PJC
You could install a remote controlled isolation device which also monitors the battery condition and automatically disconnects draw if the voltage is dropping as well as offering some anti-theft protection: https://www.antigravitybatteries-uk.co.uk/battery-protection/powerlock-battery-protector.html

There may be other similar things available online at less cost - I just recall seeing this one at a show a while back.
. Some of us bought a Battery Brain - it does just that and is a doddle to fit.