Constant Voltage method is the recommended method of charging for Sealed Lead Acid batteries. The concept is based upon using a predetermined voltage and a current limit to provide a charge cycle. Since Lead Acid batteries will not be harmed by extended periods of charge, the applied charge can remain applied indefinitely. This method is also prominent with Float Charge applications.
Float Charging is a commonly used term when a battery is used in a standby application. The concept is based upon the battery always being ready to be used if the alternate power source is no longer available. A float charge is applied either consistently for indefinite amounts of time or by way of monitoring the state of charge of the battery and not letting the battery get below a particular percentage, and re-applying a charge.