[Greg in Oz]

Do not use the car!

You have described all the sypmtoms of a failed alternator regulator. The output of the alternator is not being controlled and is supplying excessive voltage and overcharging the battery. Not only will this destroy the battery, you risk destroying anything electronic in the car (including engine ECU and ignition system, cruise control, audio system, etc) burning out lamps and burning out the alternator. At the moment it is only the battery that is struggling to prevent the voltage from rising from the usual 14 volts to many tens of volts! Do not use the car until it is repaired. Chances are the fuse on the over-voltage protection relay will also have failed and will need replacement. Without this being done the car will run, but not well.

 

[Greg in Oz]

Alternator repair

Being a '93 it will probably have the later style alternator which is not intended to be serviceable. The repair is to simply replace the alternator with a new one. This is an easy job for a DIY type but unfortunately not cheap. If it happens to have the early series alternator, the regulator can be removed from the rear of the alternator and replaced with a new one. This is a less costly option if it has the early alternator (and it has sustained no other damage through the overcharging fault). If the car shows any signs of not running properly (inconsistent idle speed, difficult starting, etc) I would also check the fuse on the over-voltage protection relay (behind plastic cover behind battery). If you decide to have the workshop do the repair, I would be reluctant to drive the car 25 miles with the fault present.