Yes, a transformer/rectifier can be used but it must be DC using a REGULATED power supply holding a minimum of 13.6 volts to maximum of 13.8 volts. This voltage is equal to the 'float' voltage that an Odyssey EPS battery charger supplies. Higher voltage (say 14.8 as used under a boost charge) over a period of hours will shorten the life of the battery considerably. Voltages higher than 14.8 will overcharge the battery in a short time and damage the battery beyond repair. This may include the bulging of the case itself.