Originally Posted by wikipedia

Pulse

Some chargers use pulse technology in which a pulse is fed to the battery. This DC pulse has a strictly controlled rise time, pulse width, pulse repetition rate (frequency) and amplitude. This technology is said to work with any size, voltage, capacity or chemistry of batteries, including automotive and valve-regulated batteries.[2][3] With pulse charging, high instantaneous voltages can be applied without overheating the battery. In a Lead-acid battery, this breaks-down stubborn lead-sulfate crystals, thus greatly extending the battery service life.[4]

Several kinds of pulse charging are patented.[5][6][7] Others are open source hardware.[8]

Some chargers use pulses to check the current battery state when the charger is first connected, then use constant current charging during fast charging, then use pulse charging as a kind of trickle charging to maintain the charge.[9]

Some chargers use "negative pulse charging", also called "reflex charging" or "burp charging".[10] Such chargers use both positive and brief negative current pulses. Such chargers don't work any better than pulse chargers that only use positive pulses.[11][12]