Bule irratic at best The Bulle clock was designed to operate on the voltage of one single dry cell, one and a half volts. Eratic rate and or gathering extra teeth of the ratchet is a fault of excess pendulum motion. The motion of the pendulum is seriously affected by the battery voltage which varies both with temperature and of course the age of the dry cell. Both variables are overcome by the compensation spring adjustment. Many Bulle clocks have lost the spring. It's made of very fine steel wire and requires steady fingers and keen eyesight to replace.