Apples and oranges
It is true that Ni-Cad's are best maintained on a cycle of complete discharge/full recharge. This does not apply to deep cycle marine wet cells. They are deep cycle as compared to standard cranking batteries typically found in automobiles, not Ni-Cad's. In a nut shell, the difference is this. Cranking batteries have lots of thin plates sitting in the electrolyte for maximum surface area (eclectron flow) for a large amount of amps available rather quickly, and deep cycles have fewer, thicker plates for steady discharge over time. As anyone who has had a hard starting car knows, if you have to crank a car starter too much, your battery capacity, which is available quickly, is also lost quickly. Too many hard starts and your car battery is dead in a hurry. it has been fully cycled too much, too often. When your car starts right away, the battery is immediately replenished by the alternator, preventing deep cycling, and thus improving life. Ah, the wonders of readily avaiable power. Actually, the LESS you discharge your deep cycle, the better. The problem is the catch 22 of needing battery power over long intervals of time without re-charging. A battery discharged to 60% cpacity will live longer than an identical battery discharged to 50% capacity, all else being equal. I will also mention that in my experience, the best deal, dollar for amp hour are two 6v golf cart batteries wired in series (to create 12v). They are about half the price of deep cycle marines. When paired, they have almost twice the available amp hours for the same price. I use a dual bank, one being a typical 12V marine deep cycle, and the other bank the pair of golf cart batteries. I can discharge both banks to around half capacity and get almost two hours of power from the g-c's to the marine's one. After three years of use, the only noticable difference has been the price. Although my needs don't require cranking amps at the ready (out bard enginge, etc.), I keep the marine battery because it does have more cranking amps available, if the need should ever arise. Batteries have the potential to be an expensive hassle. Hope this info prevents a little of each.--Rico
