re: Good boat batteries?

The group numbers refer to the physical case size of the battery. There are overlaps in storage capacity between case sizes, in that a better quality group 24 may have more amp hours than a lesser quality group 27.

The CCA ratings are significant for motor cranking applications. The reserve capacity number is significant if you are using a battery for house banks, bait well pumps, trolling motors and such. The reserve capacity number is a measure of how long a battery will provide a constant 23 amp load in minutes.

A starting battery will usually have a higher CCA rating but lower Reserve capacity than a Deep Cycle battery of the same group number from what I have observed.

A deep cycle battery will perform as well as a starting type battery in most applications but you may need to jump up a group size to get the same CCA rating. However, the starting battery will expire more quickly if you are using it under heavy sustained loads such as a house bank or trolling motor power.

Then there are the AGMs! They perform like deep cycle batteries, but self-discharge more slowly and can be recharged more quickly, but at a price premium!