Float Charge - SMA SUNNY ISLAND 4548-US Operating Manual

23 Glossary SMA Solar Technology America LLC

Float Charge

Maintenance charge: Allows the batteries to be slowly charged to a state of charge of 100% without
the negative effects of overcharging. Complete charging to 100% using float charge takes several
days. For this reason, float charge is more important for battery-backup systems and less important
for stand-alone grids.
Sealed Lead-Acid Battery
A type of battery in which the electrolyte (a mixture of water and sulfuric acid) is bound into a gel.
This is a type of a sealed or valve regulated lead-acid (VRLA) lead-acid battery. A gas mixture
(hydrogen and oxygen) is always generated when lead-acid batteries are charged, and in normal
operation this internally recombines to form water. This removes the need for regularly refilling the
battery cells with water, which is why these batteries are often described as "low maintenance" or
even "maintenance free" (see also AGM batteries). Gel batteries are available from many different
manufacturers for a wide range of applications. There are gel batteries for high current applications
but also for cycle operation with very high deep discharge cycle resistance.
Protected Loads Panel
See "Stand-alone grid system".
I-Loop
I - Loop enables generators with inadequate voltage regulation to be used in the Sunny Island system.
Stand-Alone Grid System
An energy generation system that supplies electrical energy completely independently of any external
electrical energy supply.
Constant Current Phase
I-Phase: The charging phase in which charging can be done using the maximum allowable charging
current.
Capacity
Describes the storage capability of a cell or battery, specified in Ah (ampere-hour).
The capacity of a battery is heavily dependent on the charging cycle, the amount of electrical current
strength drawn and the temperature.
State of Charge
Describes the current amount of charge that can be drawn from the battery, in percent of the nominal
capacity (100% = battery full, 0% = battery empty).
Maximum Power Point "MPP"
The operating point (current/voltage characteristic curve) of a PV array where the maximum power
can be drawn. The actual MPP changes constantly depending e.g. on the level of solar irradiation
and the temperature.
236 SI4548-6048-US-BE-en-21 Operating Manual