deep cycle marine
Generally speaking, an Oday 22 doesn't have a lot of high drain power needs so any marine grade, deep cycle battery will do. You certainly don't need one of those expensive gel units. Marine batteries come in a few flavors: deep cycle batteries that provide power for things like lights, radios, stereos, gps, etc; starting batteries that are good for providing quick, high energy jolts of juice to start engines; and dual purpose batteries that are made to do the job of both a regular deep cycle and starter battery. No engine to start? Easy choice: pick a no maintenance deep cycle battery that fits in your existing battery box. Car batteries won't do; they are really starter batteries and will not last long if you try and draw power from them to run the vhf, lights, etc. You can get a marine battery at any chandlery. I have used the BoatUS/West Marine house brand on my Oday 23 and have had great luck. If you want to save some money, Sears used to have a Diehard RV/Marine model that I bet is cheaper. You will have to keep the battery charged or it will die. You can take it home and charge it a couple of times per season, or buy a solar trickle charger.