Do you reckon a 2nd battery will charge ok and everything will be ok ?

Thinking of having a 2nd one with an inverter for operating&charging 220v like a laptop.

There are electrical systems that can be fitted, so that a 2nd battery can be safely charged, and if you check out some of the Caravan/Camping equipment suppliers, you should find what you're looking for.

Keep in mind that the 2nd battery will need to be fully secured, as much for your own safety, as for any laws/regulations, and if you're not confident with electrical systems, have the job done by a service provider.

I am going to say yes, however into the nitty gritty we go....

You will need imo an isolation diode inline with the +, this will allow positive charge current to pass to the 2nd battery but not back to the cars main battery or electrics.

I believe the fusion has a smart charge / monitor system for it's primary battery, (it is described in the manual somewhere around the alternator section if i recall correctly).

However - how does the alternator know that this 2nd battery is charged fully or not ? it doesn't, so you are at risk of overcharging unless you fit a charge controller... or have an inline switch to manually isolate it.

Example is using a solar panel to charge a workshop car battery (which supplies a 600w inverter PSW), in my case i have no charge controller as the current from my panel is 1amp max output so i use it as a trickle charger, but if i was to fit a risen solar panel which i will be doing in the future then i will need a charge controller as the panel can provide 8.9amps... again the panel doesn't know if the battery is charged or not and the battery could overcharge, swell, spill or catch fire.

Oh and don't overlook the current required for the inverter, mine just for a 240v led striplight, 65w soldering iron / 200w reflow hot air station runs at 14amps.

If it's just a laptop charger you need then using a 12v to 19v for example, buy a buck up converter that runs off the cigar lighter, safe and more efficient.

If you go down the inverter and second battery route, then a Li-ON battery will be much more efficient and safer (imo) than a lead acid cell. The discharge on lead acid is crap, Li-ON stay up on voltage whilst maintaining current. Look for graphs on this and you will see how bad lead acid are.

thanks for the answers, I will check further and once done (will take some time), will post back here