Deep cycle batteries for marine and RV use are designed to handle deep discharges between charges. A typical deep cycle battery will be rated around 100 to 125 amp hours of capacity. You should not plan to use a regular automotive starting battery, especially for high power transmitters. Starter batteries are designed to put out a huge current flow for the few seconds it takes to start your vehicle's engine. Most automotive battery chargers available today are switch selectable between charging starter batteries and deep cycle batteries.
Some hams successfully leave their battery on the automatic charger all the time.
If you do this, be sure that the battery charger is an automatic model that will stop charging the battery when fully charged. In many instances, you can also leave your radios connected directly to the battery simultaneously with the charger. This will provide you with an inexpensive, reliable and ample power source during power outages. If you must keep your battery inside, buy a gel cell-type battery. This type of battery uses a gelled electrolyte, and is sealed so that it will not vent hydrogen gas nor spill acid inside your house.