Radars have a heavy power draw compared to other marine electronics
. Especially true of older radars using CRT video displays. The other big draw is autopilots, and so most cruisers use wind-vanes when not running an engine.
I think your radar is probably OK--if you need to run it start your engine or have a gen-set handy. I always had a little Honda
to run my electric
fans and any electronics
if the batteries dropped to 12 volts or less. Marine
fans are expensive and noisy--so I used domestic electric
fans through a 12 DC to 240AC sine-wave inverter
. SO MUCH cheaper. Big inverters so one can use a vacuum cleaner or microwave oven
are far more expensive--but still an excellent idea and worth installing--but you need the good battery
bank plus back-up gen-set. I wired my AC outlets and my DC outlets and feeds in separate PVC ducts.
As for your batteries--you need to have a really good battery
bank on a yacht. Three hundred ampere hours is a good starting point--which equates to a couple of tractor batteries which should set you back a couple of hundred bucks and last about two years or longer. If you go for deep cycle betteries they will last twice as long or longer, but you will need a separate starting battery and a separate windlass
battery if you use one to raise your anchor--and the electronics to separate the charging
and load drain for each.