Merlin 40A for shore power, into 3x batteries, self-fitted. Does the job. Also Merlin Alternator Regulator, self fitted. Good value, but awful fitting instructions. Once I fitted it, it also does the job.
Just make sure it's an 'intelligent' charger, which charges initially at around 14.4v, then switches to a maintenance level of about 13.6v. Such a machine can then be driven by a small petrol genny for a shorter top up.
Multiple voltage input is common, and useful if you're going to a 110v area.
Added bell and whistle would be a 16v + option for de-sulphating.