Most of solar controllers have PWM mode, PWM refers to Pulse Width Modulation.
PWM is often used as one method of solar controller float charging. Instead of a steady output from the solar controller, it sends out a series of short charging pulses to the battery - a very rapid "on-off" switch. The solar controller constantly checks the state of the battery to determine how fast to send pulses, and how long (wide) the pulses will be. In a fully charged battery with no load, it may just "tick" every few seconds and send a short pulse to the battery. In a discharged battery, the pulses would be very long and almost continuous, or the controller may go into "full on" mode. The solar controller checks the state of charge on the battery between pulses and adjusts itself each time.
The downside to PWM is that it can also create interference in radios and TV's due to the sharp pulses that it generates.
Wellsee PWM type includes 12V/24V 6A/10A/15A/20A/25A/30A/40A/50A/60A & 48V 40A/50A/60A specifications, the model is WS-C2415, WS-C2430 and WS-C2460.
Load, or "Low Voltage Disconnect" output
Some solar controllers have a "LOAD", or LVD output, which can be used for smaller loads, such as small appliances and lights. The advantage is that the load terminals have a low voltage disconnect, so it will turn off whatever is connected to the load terminals and keep from running the battery down too far. The LOAD output is often used for small non-critical loads, such as lights. Some solar controllers also can be used as a lighting controller, to turn lights on at dark. Do not use the LOAD output to run inverters bevause inverters can have very high surge currents and may blow the controller.
Most systems do not need the LVD function - it can drive only smaller loads. Depending on the rating of the controller, this may be from 6 to 60 amps. You cannot run any but the smallest inverter from the LOAD output. On some controllers, such as the Morningstar SS series, the load output can be used to drive a heavy duty relay for load control, gen start etc. The LOAD or LVD output is most often used in remote systems, such as camera, monitor, and cell phone sites where the load is small and the site is unattended.
All of wellsee solar controllers have LVD voltage.
Sense terminals on the solar controller
Some solar controllers have a pair of "sense" terminals. Sense terminals carry very low current, around 1/10th of a milliamp at most, so there is no voltage drop. What it does is "look" at the battery voltage and compares it to what the controller is putting out. If there is a voltage drop between the charge controller and the battery, it will raise the controller output slightly to compensate.
These are only used when you have a long wire run between the controller and the battery. These wires carry no current, and can be pretty small - #20 to #16 AWG. We prefer to use #16 because it is not easily cut or squished accidently. They attach to the SENSE terminals on the controller, and onto the same terminals as the two charging wires at the battery end.
Battery System Monitor
Battery system monitors, they monitor your battery system and give you a pretty good idea of your battery condition, and what you are using and generating. They keep track of the total amp-hours into and out of the batteries, and the battery state of charge, and other information. They can be very useful for medium to large systems for tracking exactly what your system is doing with various charging sources. They are somewhat overkill for small systems, but are kind of a fun toy if you want to see what every amp is doing.
Wuhan Wellsee New Energy Industry Co., Ltd.is a big manufacturer of researching and producing solar controller, solar inverter, automotive inverter and other alternative energy products.
Wellsee has more than 40 kinds of photovoltaic products which have been exported to more than 50 countries for their high technology, perfect design, excellent quality and top service, and the markets is covering Asia, Europe, Africa, Australia and so on. The company has many femous researchers and strong production capacity with 600000 units per year, which can satisfy the requirement of all customers. The technology has reached the peak of the national photovoltaic products.
Nowadays wellsee new waterproof type solar controller which is specially used to street lights is coming for market, wellsee factory is researching new 80A/120A bigger current solar controllers, we are expecting!
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