Re: Basic marine deep cycle battery questions
Yes, if you regularly drain more than 50% then you will greatly reduce the life of the battery.
On my Catalina 25 I found that a small 20w solar panel and the 6 amp alternator in my motor was more than enough to keep the batteries charged. I could only measure charge state via a voltage meter (the depth finder had this feature), but I never saw it drop below 12 volts and only once saw it go below 12.5 volts. I did not have a shore power charger on that boat.
That boat had all LED lighting. The greatest power draw was from the autopilot.
Your VHF radio will certainly use much less power in receive mode than when transmitting (especially if transmissing at 25 watts). The manual might provide better guidance on power consumption than the back of the device.
boats that I sail on regularly: Pearson 28-2, Rondar 505, Yankee 30, Blanchard Junior