Samlex Solar SCC-30AB Mode D'emploi page 17

Sealed Lead Acid (SLA) or Valve regulated Lead Acid (VRLA) Batteries
Sealed Lead Acid (SLA) batteries or Valve Regulated Lead Acid (VRLA) batteries can
either be Gel Cell or AGM (Absorbed Glass Mat). In a Gel Cell battery, the electrolyte
is in the form of a gel. In AGM (Absorbed Glass Mat) battery, the electrolyte is soaked
in Glass Mat. In both these types, the electrolyte is immobile. There are no refill caps
and the battery is totally sealed. Hydrogen and Oxygen released during the charging
process is not allowed to escape and is recombined inside the battery. Hence, there
is no water loss and the batteries are maintenance free. These batteries have safety
valves on each cell to release excessive pressure that may be built up inside the cell.
The Gel Cell is the least affected by temperature extremes, storage at low state of
charge and has a low rate of self discharge. An AGM battery will handle overcharging
slightly better than the Gel Cell.
Non Sealed (Vented / Flooded / Wet Cell) Lead acid Batteries
In a non-sealed / vented / flooded / wet cell battery, each individual cell compartment
has a refill cap that is used to top up the cell with distilled water and to measure
the specific gravity of the electrolyte using a hydrometer. When fully charged, each
individual cell has a voltage of approximately 2.105 V and electrolyte specific gravity
of 1.265. As the cell discharges, its voltage and specific gravity drop. Thus, a healthy,
fully charged, 12 V nominal battery with each of the 6 cells fully charged to 2.105 V
will measure a standing voltage of 12.63 V at 25 ºC / 77 ºF. Also, in a healthy battery,
all the individual cells will have the same voltage and same specific gravity. If there is
a substantial difference in the voltages (0.2 V or higher) and specific gravities of the
individual cells, the cells will require equalization.
Construction of Battery Cell Plates - Lead Antimony and Lead
Calcium Batteries
During construction, both the Positive and the Negative plates are similar. Both the
plates consist of a rectangular grid made out of alloyed Lead with rectangular holes in
it as shown in Fig 3.1 below:
Fig 3.1. Grid structure of Positive and Negative Plates in a Lead Acid Battery
GENERAL INFORMATION: BATTERIEs
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