X2 won´t start with infokey after revived batteries

[eseethal]

To all the experts out there - maybe someone can help me here:

I got a X2 from a friend for repair. The 2 batteries were completely dead (9 volts / 3 volts). I could revive them sucessfully with an external applied 73 volt source, I got them to about 50 volts, now the two batteries get charged in the segway without any problems. The green lights were flashing after one night of loading. I even load tested these batteries, they seem to be working fine. But: I cannot start the Segway with the infokey. Unfortunately the second infokey is missing, so I cannot try with the second key. I checked the battery of the key (even hung it up to an external 3 volt power source), but when I hit the on/off button, I only see the little antenna-symbol, but without the little "waves" left and right to the antenna. The infokey enters the setup mode when I hit the 4 keys, but I cannot get a connection with the segway. I tried resetting the Segway by removing the batteries for the night, tried holding the on/off button for 4 seconds or more, tried starting with and without the power cord attached, but nothing helped.
Is there anything else I can look for or diagnose or try?

Thanks for any input!

Eugen