The Accutron Battery
The Accutron was designed to run on a 1.35 volt silver battery. This battery is not available today. By replacing your battery with a 1.5 volt battery could cause your watch to run very fast by double indexing the index wheel which could cause damage to your coil or index and pawl jewels.
At Clocks And Things as part of our overhaul, we “re-phase” all watches to run on a 1.5 volt 387S battery. This is the battery that is recommended by Bulova as a replacement for the 1.35 volt battery. By using this and only this battery, your watch will continue to give you many years of service.