Sludging is the release of the active material. Gassing from the battery causes
the active material to shed or slough from the plates. The active material drops as
a lead sludge at the bottom of the battery container. Sludging can cause the bat-
tery to short circuit.
Gassing from the battery during charging can cause the battery to dry out by
losing water. Check and replace the water as needed. Use distilled water. Failure to
replace the water in time can cause total battery failure and shutdown.
Selection Criteria
Battery selection hinges on many factors. Standalone PV system batteries should
have the following characteristics:
Cost efficiency
Simple maintenance requirements
Long service life
High-yield production
Ability to be charged with a small and variable current input
Recyclable
Warrantied
Battery storage is not on the listed criteria due to the varying degrees of uses.
In standalone systems that are used infrequently, a secured solar battery works
just fine. Immobilized gel and AGM batteries are good for transportable stand-
alone systems such as RVs. However, gel and AGM batteries may tend to over-
charge more often. Block batteries with gel may be preferred for year-round use.
Standard deep-cycle, lead-acid batteries have become the battery of choice in
the standalone PV world because of the combination of benefits with the down-
side of required maintenance.
Also, take into account the battery manufacturer’s guidance. Suggested
guidance includes:
Capacity at discharge
Battery-acid density
Illustration of battery service life with regard to discharge depth
Battery Installation and Maintenance
The battery is a valuable component of a standalone PV system. It stores the
excess energy for later use. Battery systems are generally designed to deliver
2 to 15 days of power under cloudy or dark days.
Battery upkeep is determined by the battery type, which was discussed earlier
in this chapter. The battery’s wiring and size influence its schedule of mainte-
nance. All batteries require periodic evaluation and maintenance. Set a thorough
maintenance schedule, and stick to it.
118 ADVANCED PHOTOVOLTAIC INSTALLATIONS
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