User Manual

RENEWABLE ENERGY APPLICATIONS
Most deep cycle batteries used in the Renewable Energy Industry were originally
designed and manufactured for use in commercial and industrial applications
where consistent charge cycles are carried out from six to twelve hours until the
batteries reach a full state of charge. In Renewable Energy (RE) applications,
a lengthy charge time is not typical and in most instances a maximum of 4-6
hours of peak charge is achieved each day due to limited daylight and varying
weather conditions. To ensure the batteries received sufficient charge, charging
systems must be adequately sized or additional charge sources added to prevent
undercharge, deficit cycling and premature battery failure.
There are two definitive types of battery-based systems used in Renewable
Energy applications; off-grid and grid-connected. Off-grid systems are often used
where a customer does not have access or chooses not to connect to a public
utility. This customer may live remotely and have chosen to install a renewable
energy system from a single or combination of renewable sources to generate and
store adequate power to run all electrical requirements within the home.
With grid-connected systems, a customer typically lives in an area where they
may experience frequent or extended service interruptions from their public
utility. This may be a result of poor weather conditions, an unreliable power grid
or natural disasters. The renewable energy system is used as a backup power
supply, meant to supplement power to support critical loads (e.g. lighting and
refrigeration) during brief outages and/or to reduce energy costs by selling excess
power generated from the system back to the utility.
DEPTH OF DISCHARGE
Depth of Discharge (DOD), is used to describe how deeply the battery has been
discharged. A battery which is 100% fully charged would have a DOD of 0%. A
battery which has been discharged by 20% of its capacity, maintaining 80% of its
capacity, would have a DOD of 20%. If a battery has been completely discharged
with no remaining capacity, the DOD is 100%.
CYCLE LIFE
Battery manufacturers rate the cycle life of their batteries by comparing the level
of discharge on the battery and the frequency of cycling. Higher battery discharge
will result in shorter cycle life. In reverse, a smaller discharge percentage will
extend the expected cycle life of the battery as the battery will provide more
charge/discharges. To provide an example of cycle life, a 48V string of 8 x 6-volt
S6 L16-HC models in series (445 AH capacity @ C/20 ) which are consistently
discharged to 50% state of charge (222 AH of capacity drawn) and consistently
recharged to a full state of charge should provide approximately 1400 cycles
before end of life.
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