WHAT IS A SOLAR CHARGE CONTROLLER AND WHY DO I NEED ONE?
Fangpusun PWM and MPPT Solar charge controller can protect the battery well in the PV System. It has Overcharge protection, Deep discharge protection, Reverse polarity protection of the load, module and battery,Automatic electric fuse, Short circuit protection of load and module and so on. EG.Fangpusun Solar charge controller, or Solar regulator is basically a voltage and/or current regulator to keep batteries from overcharging. It regulates the voltage and current coming from the solar panels going to the battery. Most "12 volt" panels put out about 16 to 20 volts, so if there is no regulation the batteries will be damaged from overcharging. Most batteries need around 14 to 14.5 volts to get fully charged.
DO I ALWAYS NEED A Solar CHARGE CONTROLLER?
Not always, but usually. Generally, there is no need for a charge controller with the small maintenance, or trickle charge panels, such as the 1 to 5 watt panels. A rough rule is that if the panel puts out about 2 watts or less for each 50 battery amp-hours, then you don't need one.
For example, a standard flooded golf car battery is around 210 amp-hours. So to keep up a series pair of them (12 volts) just for maintenance or storage, you would want a panel that is around 4.2 watts. The popular 5 watt panels are close enough, and will not need a controller. If you are maintaining AGM deep cycle batteries, such as the Concorde Sun Xtender then you can use a smaller 2 to 2 watt panel.
What happens when you use a standard PWM or Solar charge controller
Standard (that is, all but the MPPT types), will often work with high voltage panels if the maximum input voltage of the charge controller is not exceeded. However, you will lose a lot of power - from 20 to 60% of what your panel is rated at. Charge controls take the output of the panels and feed current to the battery until the battery is fully charged, usually around 13.6 to 14.4 volts .A panel can only put out so many amps, so while the voltage is reduced from say, 33 volts to 13.6 volts, the amps from the panel cannot go higher than the rated amps - so with a 175 watt panel rated at 23 volts/7.6 amps, you will only get 7.6 amps @ 12 volts or so into the battery. Ohms Law tells us that watts is volts x amps, so your 175 watt panel will only put about 90 watts into the battery.
Using an Fangpusun MPPT Solar charge controller with high voltage panels
The only way to get full power out of high voltage grid tie solar panels is to use an MPPT controller. See the link above for detailed into on MPPT charge controls. Since most MPPT controls can take up to 150 volts DC (some can go higher, up to 600 VDC) on the solar panel input side, you can often series two or more of the high voltage panels to reduce wire losses, or to use smaller wire. For example, with the 175 watt panel mentioned above, 2 of them in series would give you 46 volts at 7.6 amps into the MPPT controller, but the controller would convert that down to about 29 amps at 12 volts.
CHARGER CONTROLLER TYPES
Charge controls come in all shapes, sizes, features, and price ranges. They range from the small 4.5 amp (Sunguard) control, up to the 60 to 80 amp MPPT programmable controllers with computer interface. Often, if currents over 60 amps are required, two or more 40 to 80 amp units are wired in parallel. The most common controls used for all battery based systems are in the 4 to 60 amp range, but some of the new MPPT controls such as the Fangpusun Power FlexMax go up to 80 amps.
WHAT IS PWM?
Quite a few charge controls have a "PWM" mode. PWM stands for Pulse Width Modulation. PWM is often used as one method of float charging. Instead of a steady output from the controller, it sends out a series of short charging pulses to the battery - a very rapid "on-off" switch. The 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 solar charge controller may go into "full on" mode. The 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.
WHAT ARE THE "SENSE" TERMINALS ON MY CONTROLLER?
Some solar charge 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 accidentally. They attach to the SENSE terminals on the controller, and onto the same terminals as the two charging wires at the battery end.