1998 Honda Accord what would cause a short to the voltage regulator

1998 Honda Accord mileage: 157,000. What would cause a short the voltage regulator inside the alternator and at the same time blow the headlights, interior lights, dash clock and damage the radio? The reason I ask is that after I got my car back from the body shop from collision to right front of vehicle (passenger side - battery side) they claim the electrical problems I now have were not a result of the accident since the battery tray was not damaged? This does not sound right to me. After further investigation the battery left cell was either shorted or somewhere inside there is a break thereby making it "open circuit". Would the damage to the voltage regulator have happened during the impact or during the trip home after the accident? Currently the alternator is punching out 18V. A little insight here would be appreciated.