Linear Current Boosters for Pumps
How They Work & What They Do
Linear current boosters
can be used to eliminate solar batteries and oversized solar
arrays for operating direct current motors for a number of
applications including pumping water and operating
ventilation fans or ceiling fans when the sun is shining. Here are some terms
you need to know. If you need more background read my
calculations math tutorial.
Current = Amps
Power = Watts
Force = Volts
Volts x Amps = Watts
Solar panels are a
relatively constant source of force. Force is measured
in volts. A solar panel exposed to sunlight early in
the morning or late in the afternoon will
produce volts, but the amps produced may be close to zero.
Volts times amps equals watts. Without enough current to
get the power moving, the
motor will not run.
So, even though the panel
may be producing volts, if the amps are near zero
the watts will be very low to zero. With no amps, there is
no current and a DC motor will not run.
pump motor that requires about 14 amps at 12 volts (like the
Simple Pump solar water
well pump motor) that requires about 170 watts of solar
panel to run panel direct during full sun exposure may need
as much as 320 watts of panel to run earlier in the morning
and later in the afternoon, or to run at all on a cloudy
day. A linear current booster increases amps by
sacrificing volts to create enough watts to allow the motor
How A Linear Current Booster Works
Linear current boosters do two things: provide panel feedback and convert volts to amps.
When a solar panel is connected directly to a DC motor, if
the motor does not receive
enough power (watts) to run, this creates what the panel
perceives as a short circuit which limits the panel voltage
and panel current, a self defeating situation. The linear
current booster provides feedback to the panel that the load
of the motor is really less than it is. This allows the
current (amps) and volts from the panel to remain at
maximum, thus delivering full available power to the
The second thing a linear current booster does is convert
available volts to amps. For example, most 12 volt panels
will actually produce 18 to 20 volts. Using high speed
switching power supply technology, an input of 11 amps at 18
volts may be output by the linear current booster as 15 amps
at 12 volts. Power out equals power in minus a small
conversion loss but at lower volts and higher amps. 11
amps at 18 volts = 198 watts. 15 amps at 12 volts = 180
watts. The efficiency loss equals about 10 percent in this
example. Most linear current boosters have an
efficiency loss of about 8 percent.
This current boost creates the additional amps needed to
start the motor. The trade off is lower motor RPMs.
Lower voltage means lower RPMs. But, the motor is running!
Without the linear current booster the motor will not run
until the solar panel delivers watts at near full capacity.
When the current exceeds the resting torque of the
motor the motor starts turning.
Another Linear Current
Another advantage a linear current booster provides for
running a DC motor is that while
the motor may be running at lower RPMs, the additional amps
provide an increase in motor
torque, which allows the motor to better power a fluctuating
load, or keep a pump operating when a cloud passes over the
solar panel. The RPMs may decrease but the motor will be
more likely to keep running. The increase in motor run
time can be as much as an additional 30 to 100 percent
compared to running solar panel direct without the booster.
We normally stock these linear current
LCB 12/24-7, array
volts 12 or 24, current maximum 7 amps
LCB 12/24-15, array
volts 12 or 24, current maximum 15 amps
LCB 12/24-30, array
volts 12 or 24, current maximum 30 amps
Other models are
available on special order.
Please contact us for assistance with selecting the
right linear current booster for your application.
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