Twin Alternators and fitting leisure battery HELP PLEASE

[welshbird]

Evening all
I would like to fit a leisure battery, inverter etc to have some power available for the odd overnight where no ehu is available but can't quite figure out exact parts list required. I currently have just a tin top T25 with full width r&r bed, that's the extent of the interior. (I don't plan to fit any units, sink or kitchen in, I have an awning, travel fridge and gas cooking stove). I would want it to provide sockets for 230v, 12v and USB and ability to charge leisure battery via ehu when available and eventually add the ability to charge via portable solar panel.
My van has twin alternators fitted:
● how will this affect the wiring and fitting?
● do I still need a split charge relay?
● will I get away with an underseat leisure battery or should I relocate battery and get a deep-cycle?
I have tried wiki, Google etc but can't find anything about working with twin alternators and whilst I am reasonably handy I lack confidence with vehicle electrics so any help will be much appreciated!

[ZsZ]

Check your second alternator as OE fitted ones were 24V for the military equipment.
You can wire the leisure system separately to the second alternator then you don't need a split charge relay. But if you want a 12V system then you need a 12V alternator.
You will need a battery charger for the solar panel.
The second alternator will cause some extra fuel consumption when used.
230V sockets ran from a battery would need a big inverter together with a big battery pack.
Under the seat you can fit a ~80Ah leisure battery (or deep cycle if you don't have the lid) I assume you have a diesel, so you can have two of them wired parallel. With lead-acid deep cycle you can use around the half of the rated capacity so 1 battery is 40Ah 2 batteries are 80Ah. Depends on your appliances but with 80Ah you may have enough off-grid power for a weekend.

[welshbird]

Thanks so much for the advice