Yes you can! Tho clock and date has to be set everytime you start your amiga (if you want/care) and all files edited/created will allways have the same annoying date 
But other then that it will work just fine 
My 4000 has been running without a battery for ages - it just runs FACTS (
http://www.unsatisfactorysoftware.co.uk/index.php?pg=facts) when it connects to the net!
Get that battery out ASAP though! It'll kill your motherboard!
