Early EU3000is generators were shipped "dry" and included an electrolyte pack. Dealers were expected to fill the battery with electrolyte, charge it, and install into the chassis of the generator when delivering it to customers.
In reality, many were shipped/delivered to customers in unopened boxes. This was a problem for some customers not accustom to safely handling electrolyte and lacking a charger to properly prepare the battery. Of course, the big advantage was the generator could sit in the box indefinitely with no worry about a battery going flat.
Fast-forward a few years, and AGM/factory activated batteries are considerably improved. They can retain a reasonable charge for almost a year in storage. It was decided to change to an AGM battery, as Honda figured the units would rotate through the warehouse and dealerships fast enough that a fully-charged battery would survive and make it to initial retail delivery just fine.
A that was a good 4-5 years ago. So far, its been a good decision.
Short answer: If your EU3000is is less than 4 years old, it's got a factory-sealed battery that requires no top-off of distilled water. If you have an older one, with screw-cap type covers (6 of 'em) then you've got an older traditional battery that should be inspected if you are having battery charging issues.
Caveat: I work for Honda, but the preceding was my opinion alone.
