Solar, MPPT, Zig CF6, 2nd battery compatibility, t25 2L CU

[Lord-won't-you]

Hi, I have an '82 t25 2L CU high top camper with a zig CF6, only one starter battery, but there are the cables for the leisure battery (under passenger seat).

I want to fit a 100-130w flexible solar panel with a MPPT controller (victron 75/15?), and a new leisure battery, the power of which being the max I can fit into the under passenger seat battery compartment, 80Ah-100Ah, I imagine

Electrics confuse the absolute heck out of me  , but I can follow any good instructions when in layman's terms.

Firstly, if I use an AGM battery, will there be any compatibility issues with the lead acid starter battery and the required charging voltages between the two, when using both the MPPT and zig unit? Or do I need to stick with a conventional lead acid leisure battery?

Secondly, which is my best wiring plan option, using both the MPPT and Zig unit? I gather the zig unit means a split charge relay isn't needed in the set up?

I don't intend on using the 240v hook up, but I don't see any point in removing it, unless there's a distinctly better option than the zig CF6 for power distribution.

Thirdly, it has a 240v only 60w rated fridge. Am I right in thinking that to replace it with a 12v only compressor fridge with ice box, is a much better fix for a 12v set up, than using an inverter to power the 240v one that's fitted? (I could certainly use the 240v mini fridge up in my house in my 3rd floor bedroom in this warm weather if so  )

I know there's the option of a B2B charger. but I'm unaware of any specific advantage of such, in the set up I require  

Any help would really be very much appreciated.

 Thanks for reading

[TwinTurbo]

you have ~30% inverter loss going from 12V to 240v , so going with a 12v Fridge will be more energy efficient. 

My system just uses an old Lead battery at present. the solar goes into the MPPT , I removed the battery feed from the ZIG and put it on the MPPT battery side and put the output of the MPPT back into the ZIG. 

[Lord-won't-you]

you have ~30% inverter loss going from 12V to 240v , so going with a 12v Fridge will be more energy efficient. 

My system just uses an old Lead battery at present. the solar goes into the MPPT , I removed the battery feed from the ZIG and put it on the MPPT battery side and put the output of the MPPT back into the ZIG. 

Thanks TT, useful info.

Is the MPPT charging both batteries, and does that set up mean the leisure battery doesn't get charged when driving? 

[TwinTurbo]

It only charges the leisure battery. No change to the split charge system and everything seems to be happy so assume it's still charging on alternator.