AGMs and Gels ARE lead-acid batteries! They're just not flooded, i.e., don't have a liquid electrolyte.
Which type to use depends on your electrical
setup, on planned usage and, to some extent, on your wallet. You said that money
is no object and that you plan to do "ocean sailing".
surely have a lot to recommend them but, unfortunately, longevity and reliability
aren't among their best traits. Some have had excellent experience with them, have treated them right, and they've lasted a relatively long time. Others have had sudden and catastrophic failures with them, including one poor chap who was several hundred miles from the Azores
. For ocean cruising, this would be a cautionary note for me. Their ability to take a huge charging current
is great, but you must have sufficient onboard charging capability to realize the benefits. Fitting AGMs to boats with standard alternator
setups often leads to burning up the alternator
are an excellent choice for boats which spend most of their time in a marina plugged in. I have some gelled golf carts in my basement which spent the first 10 years on such a sailboat -- only doing weekend trips and the occasional longer trip -- and have spent the past four years in testing. They still test at over 90% capacity...very, very good, indeed. However, as was mentioned, gels can be killed by overcharging as well as undercharging. AGMs are a bit more tolerant for sure.
Most robust is the standard flooded battery
. Typical longevity is about 3-5 years, but some who treat their batteries well have gotten more. At the top end of the flooded battery
chain are the very excellent batteries made by Rolls/Surette. These heavy duty deep cycle batteries typically last more than 10 years, and sometimes 15 years or so. They can take more abuse than AGMs or gels, and are a proven design. However, they must be maintained by keeping clean and by ensuring that the water
level stays above the plates (HydroCaps or WaterMiser Caps help a lot in this respect).
So....given your parameters of "cost no consideration" and "ocean sailing", I'd choose Rolls/Surette every time. At least for the present, until something provably better comes along.
In this respect, I and others had high hopes for Firefly Technologies (a Caterpillar spinoff). After a long gestation period, they finally came to limited production of group 31 batteries for the military and trucking industries, but recently filed for bankruptcy. Damn!
Other technologies are on the way, but I think the watchword should be "any time now" :-)