You may want to consider Powell's advice. I know that spending another $80 is probably pretty difficult for you to accept right now, but it might still be worth the risk. You might even, if worse comes to worse, get a much better offer for the system "as is" if it includes the original battery.
I just don't think you'll get much for a battery-less Bionx system on the used market (due to their "proprietary" battery design). This may give you reason to consider paying the $200 (@ dealer cost) so that you might sell it as a working system. You should first, of course, determine how much money you might get for your used Bx system (both working and non-working).
Below are some links that you might want to look through (you probably have already seen these, but I figured I'd post them just in case):
http://www.nycewheels.com/bionx-diagnostic-mode.html
http://www.nycewheels.com/bionx-diag...ery-gauge.html
http://www.nycewheels.com/bionx-batt...-charging.html