There is more than one way to skin a human.
A lot of folks seem to run a True isolator and Stinger relay.
@trigger runs a second battery, in parallel, essentially just adding to his total available amp hours, relying on himself to manage the draws on the system.
Personally, I will be running an additional Mighty Max 35ah SLA battery, mounted under my p52 driver's seat, tied into the Main via a Blue Sea Mini add-a-battery switch/relay. From there, I intend on running it through a Stinger relay controlled by a main power switch. The Stinger will then energize the fused relay boxes for the various accessories and the power lead for the winch contactor. In theory, this should allow me to shut down all parasitic draws (I hear wireless winches will do this) as well as allow me to keep the BS-MAAB in the ON position while trickle charging the main/Aux batteries.
I think you are supposed to keep batteries of like styles together if they are on the same charging circuit, i.e. SLA/SLA, AGM,AGM, Lithium/Lithium, etc. Someone correct me if this is wrong.