Proper use of 2nd battery

Been floating/charging my 120a/h battery whilst using devices at same time for some 12 mths or so without any damage to charger or 12 volt items. I am using a Projecta 6 stage 21amp charger, connected anytime am on the grid or rare occasions the gennie is running.The music centre for caravan is only 12 volts so is always running when van ij use or am working on it. Unlike the present where everything is direct wired, down the lline will be installing a fuse box purely for isolation purposes.

Your "12 volt" lead acid battery actually has a no-load voltage of about 12.6 due to its electrochemistry. When charging, the charger (or the alternator) will be called on to deliver up to about 14.5 volts, or for some (eg calcium doped) batteries up to about 15 volts.

Any gear intended to run from a "12 volt" battery should handle this full voltage range.

Cheers

John

I'll answer you question none technically.......

You have connected your devices correctly and it's OK to charge the battery with your 240v charger at the same time whilst using them.

The fuse for your gear like laptop, lights, fridge and what ever else should be as close as possible to the power source (in your case your secondary battery).

Your fuse box should come straight of the positive (+) terminals on your battery and the negative (- or earth) of the negative terminal of your battery.

The 240v charger should be connected directly to the positive and negative terminals.