Why is one battery marked #1 on the Voyagers?

[damaltor]

Here it is:
http://www.hpmuseum.org/cgi-sys/cgiwrap/...ead=228996

So that might be a fairly undefined reason - it still could be that it is just to mark a battery like rprosperi said. All battery changing/short circuit/mem loss reasons are invalid for me, as there used to be a plastc flap on #1 and #3 on early models (and a single flap on #3 on the later models), so the only defined thing is that the middle battery will be put in last.