Don't limit yourself to just the typical deep cycle batteries you may find at a chandlery or marine store. This is a 400Ah bank consisting of two Trojan L16 size 6V batteries. While L16's are much taller than 12V batteries, or even GC2 6V batteries, they take up less foot print. For this owner he had the height but not the foot print. These two batteries are sitting where two Group 27's used to be and he now has 400 Ah's vs. approx 180 in the same foot print.
"But RC what if I don't have the height to fit actual deep cycling batteries?"
There are a few way's to look at this:
#1 Accept your limitations, accept the marketing is misleading and just stick with a premium quality "light cycling" G-24, 27 or 31 flooded battery such as a Crown, Trojan, US Battery and replace it when it dies. Rolls actually makes a fairly deep cycle G 27 & 31, though not quite the same as their GC2's but closer than most, however they are God awfully expensive.
With good care in a coastal cruising application light cycling batteries can still certainly deliver an acceptable life for the cost outlay. If you practice good battery care you may be able to eek out another 6 months to a year beyond where you are now. Cost is minimal & no modifications. Upgrade cost = $
#2 Move to a premium AGM (Lifeline, Odyssey, Northstar) or GEL (Deka, Trojan or Sonnenschein/Prevailer) battery. In the G-24, 27, 31 4D & 8D both premium AGM and GEL are deep cycle. AGM's & GEL's are arguably a bit temperamental in how they are cared for and charged and these really need to be installed as a "system". The charging system upgrade costs can far exceed the cost of the batteries. These batteries are simply too expensive to not install correctly. Done correctly AGM can often approach 6V GC2 life and GEL's often exceed it. Of course, like anything, there are always outliers. You can murder expensive AGM's & GEL's just as fast as pseudo batteries if the system & use is not done correctly. GEL batteries are pretty much the hands down kings of small case cycle life. The Deka GEL is rated at 1000 cycles. I have a number of GEL banks out there well beyond ten years and one into its 15th. My friend Bruce went around the world TWICE in the same set of GEL batteries..... Upgrade cost = $$$$$
#3If you are going to be doing some serious cruising, consider relocating your house batteries and fabricate / build a new space for them. You can leave the starting battery as a deep cycle pseudo type, in the original location, and just revamp the house bank. Upgrade cost = $$
Some times when you factor in how long you plan to keep the boat, sticking with light cycling batteries, despite the hit in cycle life, it may win the value game.
