Batteries – What’s the Difference
What is the difference between a gel cell,
an AGM and an SLA battery?
W
ith everyone rushing to win independence
from Zesco by installing inverters and solar
power, one needs to understand the differences
between the various types of batteries offered
in Zambia. A gel cell or gelled electrolyte is a
sealed battery containing semi-solid electrolyte
and may also be identified as a sealed lead acid,
AGM (absorbed glass mat) or VRLA type battery
(Valve Regulated lead Acid).
AGM batteries are sometimes referred to as
starved electrolyte because the fiberglass mat
contained within the cell is saturated only 95%
with acid and there is no excess liquid. Nearly
all AGM batteries are valve regulated. VRLA
batteries are designed with a valve that allows
the battery to keep a slight positive pressure.
1. What is a marine or deep cycle battery?
These are actually different types of batteries.
The common marine battery is often rated to
marine cranking amps. It is designed to offer
a quick shot of amperes in a very short time
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FARMERS GAZETTE
November 2015
span to start an engine. These batteries can
provide thousands of starts but can usually only
withstand 50 or so cycles – from flat to fully
charged. A deep cycle battery is designed with
the capability of being discharged and charged
hundreds of times. Many of these batteries may
be totally discharged or drained before they are
ever recharged. A deep cycle battery has thicker
plates in order to better withstand the distorting
effects of cycling. An ordinary automotive
battery has relatively thinner plates.
2. What is the shelf life of an SLA battery?
All sealed lead acid batteries self-discharge over
time. If the capacity loss due to self-discharge
is not compensated for by recharging, the
battery capacity may become unrecoverable.
Temperature also plays a role in determining
the shelf life of a battery. B
atteries are best stored at about 21°C. When
batteries are stored in areas where the ambient
temperature varies, self-discharge can be
greatly increased. Check the batteries every
three months or so and charge if necessary.