I think they "should" say no. The list of prohibited items says:
QUOTE
For safety and security reasons, dangerous goods such as those listed below, must not be carried in passenger's baggage (checked or unchecked):
...
corrosive materials such as mercury (which may be contained in thermometers or blood pressure gauges), acids, alkalis and wet cell batteries
UNQUOTE

Even though it is sealed, yours is still a wet-cell battery, containing a corrosive substance - acid.

Having said that, the rules also prohibit carriage of compressed gases, which didn't seem to faze CX some years ago when I asked if I could check in a small domestic freezer (and I specifically mentioned the compressed gas in the freezer) - the answer was yes, and they took it on board (as check-in) with no problems!