by Sarah Latimer, Survival Blog:

(Continued from Part 1.)

CHARGING OVERVIEW

At a high level, the stages of charging a battery include: bulk, absorption, and float. On batteries that have been discharged deeply, there is also an equalization charge required.

Bulk charging demands high current. Absorption charging requires less current but a slightly elevated voltage. Float is your trickle charge which has low current at about one volt above the stasis voltage of a charged battery.