I run the same Optima 31 (blue top) battery that you are suggesting. I also run the CTEK 3300 charger to charge it. The charger puts out ~3 amps and charges the Optima very well. The charger has an "Optima" setting on it (charges at/to 14.7 for the Optima). CTEK rates this charger for batteries from 2 to 90 Amp hours. I monitor this with an "E" meter and can verify the results, and I'm quite happy with it so far. I keep my boat in a moorage with shore power to keep the battery topped up. I run a depth sounder,VHF, Nav lights, stereo, and interior lights. No LED lighting. After a full day of sailing, using everything that I want/need, the charger usually kicks into float/maintaince before I'm done putting away the gear and securing the boat for the night.
Best of luck
Last edited by 75R20; 04-10-2010 at 03:37 AM.