Read this wikipedia entry, its got all that you need to know. Any questions just ask here.
en.wikipedia[dot]org/wiki/Battery_charger
replace '[dot] ' with ' . '
Quote: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
Wow, that information was of really good help. I however, don't understand one thing, how are the batteries charged, when we push the accelerator in neutral?