M3 E36 convertible alarm model 3T-EWS?

Hi Hope someone would be able to shed some light on this for me. Due to the cold and infrequent use the battery on my car has run down so unable to start car or unlock it using key fob. Therfore I've had to open doors manually with the key. I've charged the car battery and car starts ok but as soon as the battery terminals are connected the alarm sounds and doesn't switch off. The key fob can lock and unlock the doors as if the alarm is being armed and disarmed but the alarm still sounds and wont stop untill I disconnect the battery terminals. It seems as if the alarm has switched to its batteyr back up. But is there anyway of resetting the alarm or disabling the siren? Any suggestions will be most appreciated.
cheers.
sarge.