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Charge controllers
protect batteries from being overcharged.
Charge
controllers or voltage regulators protect batteries from being
overcharged, which can shorten their life as well as the life
expectancy of the equipment being powered. Electronic circuitry
in the regulator measures battery voltage, which rises as
the battery state-of-charge (SOC) increases. At some voltage
(which is different for different types of batteries at different
temperatures), the regulator will limit the charging of the
battery.
Regulators
for photovoltaic (solar electric), wind and water powered
systems perform the same function as a voltage regulator in
an automobile. However a regulator from a car will not work
in a remote power system due to a few differences. Advanced
features found in most charge controllers are: low voltage
disconnect (LVD), lighting controls, adjustable settings for
different battery types, auto equalization, fusing, temperature
compensation and reverse polarity protection. Some regulators
charge using pulse width modulation (PWM) while others use
simple on/off schemes.
We carry
charge controllers from name brand manufacturers like Morningstar,
Blue Sky, Outback
and Xantrex. Contact
us for more information.
Are
charge controllers really necessary?
Most systems
have battery capacities more than or equal to 4 days of load
requirements and are typical of many PV systems used for residential
or outdoor lighting applications. The function of the charge
controller(s) in these systems is to protect the batteries
from overcharge or overdischarge.
Two systems
were tested with malfunctioning or incomplete charge controllers
to demonstrate why controllers are needed for the types of
PV systems tested here. A system at FSEC initially had a malfunctioning
controller that rarely regulated at all and which, on most
clear days, continued to try to bulk charge the battery until
sunset. This led to maximum battery voltages of 15.0 to 15.3
V on many sunny days, which is excessive for this type of
battery. As a result, the battery inthis system had very high
water loss. In the post-mortem inspection, the positive grids
of this battery were found to be severely corroded.
On the
other hand, another system at Sandia initially had no low-voltage
disconnect. As a result, the battery in this system was drained
to -1.5 V during a cloudy period. At 1.5 V, the controller
could not operate properly and disconnected the array from
the battery, locking the system into a non- functioning state.
Manual intervention was required to restart the system. An
external low-voltage disconnect was added to the system after
this incident. Note that this problem, which occurred due
to the absence of a low voltage disconnect, occurred on the
system which otherwise maintained the highest state-of-charge
of any of the fourteen systems in this test.
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