Eric Greenwell wrote:
The 302 manual makes no mention of an internal battery, so I assume
there is no need to change it. I don't know how they handle trashing the
security seal if the box is opened.

There is an internal long-life lithium battery, it just doesn't need to
be replaced on a routine basis. Eventually, I suspect, it will need
replacement (perhaps after 10 years or so), in which case the 302 will
need to be returned to Cambridge or one of its agents...

Marc