Korg DW8000, Mono/Poly, MS-20...

I was given a Poly-61 in rather poor shape by my cousin, who nabbed a
beautiful PolySix for next to nothing.  The Poly-61 is now usable,
though some of the parameter buttons are still flakey.  I recently
moved it from home to school and lost about forty presets, all
original creations.  As long as it is plugged in, my new presets
remain.  Was my loss a result of a dead battery?  If so, what type of
battery does it use?

While I'm posting, for the first time I might add, I suppose I will
ask about external storage as well.  Is there any other way to store
patches externally other than on tape?  Keep in mind I have a Poly-61
and not a Poly-61M.  While I am aware that computers and synthesizers
used cassettes for storage, I never personally experienced their use.
 Is there any special type of cassette recorder needed for storage? 
Does it have to be specifically geared for data storage?  Also, does
anyone have ideas on where one could be purchased?  Thanks in advance.

InkBlot