If the 3000i uses the same algorithm as the older models or similar, it isn't a simple "3 stage". They set the charge voltage something like 1/2 volt higher than the battery
voltage and convert the rest of the power into amperage, resetting the levels of both every few minutes as the battery voltage comes up. That allows faster, more efficient charging
than a simple "3 stage" and if you are using wet lead batteries, it also keeps the electrolyte cooler so you'll need to water
them less often.
Their older stuff (and the modified algorithm) are good, I would hope the new stuff is the same if not better. IIRC the power connections were smaller than you might want, you'd need to check that with them, versus what cabling you want to run. (Or just pigtail down if need be.)