Pulse Charger
Spring 2013 - Nick Meyer
This charger is designed much differently than most lead acid battery chargers. Where most battery chargers apply a constant current (that decreases as the charge completes), this one applies the same average current but instead does so in short high voltage "pulses". These pulses represent a ~60v square wave that is roughly ~1kHz in frequency with a very low duty cycle (High to low signal ratio). In this charger current pulses can reach over 1.5kA on a good battery with low internal resistance. Where this charger really shines is on old batteries that have an extremely high internal resistance (13v+ resting voltage but no cranking amps), in this case the high voltage allows the charger to overcome this high internal resistance and actually charge the battery without overheating it and simply boiling off all of the acid. Since it is powered by an Atmega128 that senses battery conditions and average charge current it can adjust charging characteristics to what is best for the battery, this allows a high average current "fast" charge to begin with then a low average current "rejuvenation" or "desulfation" mode that keeps the battery topped off and slowly decreases the internal resistance of old batteries over time. Since pulse width is constant and peak current varies with internal resistance average current is automatically adjusted by increasing or decreasing the number of pulses per second.
