Ctek 250se ignition cable

[Matthew123456789]

Morning I've just installed a leisure battery syestem in our caddy along with the ignition cable for a smart alternator I piggy backed it onto a fuse that starts with the ignition.

Question is how do I know that the cable is working? The syestem work fine and is charging the leisure battery but there's no lights and I can not do a voltage test on the cable to see if its life.

Thanks