Gi and Barnacle

Hello Canal Forum Folks This is my first post so, first off, hello. Let me introduce my boat. She's called Barnacle and is an aluminium hulled 28 foot former liveboat that runs off a solar and wind powered electric engine. I wonder if any of you folks could give me some advice about whether to install a back-boiler or not. I have a both a woodstove and a Mikuni diesel heater but, annoyingly the Mikuni only works when its sunny or windy. (When there is enough renewable energy to provide the battery power the Mikuni starter motor requires). In the winter my woodburner is often my only source of heat. I need to replace my woodburner because it has cracks in and I was wondering about replacing it with a woodburner with a back-boiler so that I would get hot water as well as heat in the winter. The backboiler would presumably be fitted with a 12v pump to feed water into my calorifier. I've asked every boat owner I know and I've got a lot of conflicting advice. Some say that back-boilers are troublesome and dangerous, others love them. Do you have any advice? I am particularly concerned about the safety aspect. My 12v batteries are often rather low on power in the darkest months of winter. The pump that pumps water from the back-boiler to the calorifier would need to rely on these batteries. The stove is in the lowest part of the boat so there is no possibility of installing a gravity feed radiator as a heat sink if the pump should fail. Any thoughts would be gratefully received All the best Gi (and Barnacle)