This is a portable high performance MPPT solar charge controller module that is capable of charging larger battery banks of all types. We mainly use this solar charge controller module to charge our LFP 180 Battery Moduels but the charge controller can be setup to charge other AGM or Lead Acid battery types also.
The system is housed in a military grade rugged Pelican 1500 case that has the following exterior dimensions: 18.5" x 14.06" x 6.93" . The case weighs approx 20 pounds.
The system can be used with the lid open or closed because the high power cooling fans will turn on automatically once the internal temp raises above 100F and then turn off once the internal temp drops below 80F.
The solar input port is a special 100 amp twist lock connector that will never accidentally pull out. The battery connection port is also a special twist lock connector that will never pull out on accident. The input / output ports can not be plugged in incorrectly due to the way the connectors are designed so there is no need to worry about plugging in the connectors incorrectly.
The system had a very nice digital LCD display that shows all the important information about the current status of your solar array and how its performing at any particular time. The LCD display will also show you a graph of the performance over the course of the day from sun up to sun down. The system logs data every 5 minutes in its Recent logs allowing you to view the last 24 hours. The system keeps a log of daily solar performance over the course of the last 380 days also.
The lines on the graph below represent the power output current at different Max Power Points Voltage (not VOC). To estimate the Max Power Point of your system; first you have to find out the VOC of the Photovoltaic strings connected to the solar input. For example If 5 Modules in series in one string and STC VOC rating is 36.6V, then the VOC of the string equals: 5(modules) * 36.6v(STC VOC) = 183V.
The rule of thumb says that the MPP will be around 80% of the string's VOC; 183v * 0.8 = 146.4v On the graph of the Classic model you have, the X axis represents the Battery Voltage and the Y axis is the Output current. Knowing that, go to the corresponding graph and look for the a line close to your system's MPP voltage and you can then determine the max output power for your system design.
You can see in the graph below that we are being conservative when we label the charge controller as a 1100w solar charge controller, its really capable of handling more power as shown below.
The module can charge 12, 24, 36, and 48v battery banks just fine. The higher the voltage of your battery bank the more solar input power the charge controller can handle.
Now lets talk about what the MPPT "Maximum Power Point Tracking" features do for you and how it works.
This section covers the theory and operation of "Maximum Power Point Tracking" as used in solar electric charge controllers.
A MPPT, or maximum power point tracker is an electronic DC to DC converter that optimizes the match between the solar array (PV panels), and the battery bank or utility grid. To put it simply, they convert a higher voltage DC output from solar panels (and a few wind generators) down to the lower voltage needed to charge batteries.
(These are sometimes called "power point trackers" for short - not to be confused with PANEL trackers, which are a solar panel mount that follows, or tracks, the sun).
Solar cells are neat things. Unfortunately, they are not very smart. Neither are batteries - in fact batteries are downright stupid. Most PV panels are built to put out a nominal 12 volts. The catch is "nominal". In actual fact, almost all "12 volt" solar panels are designed to put out from 16 to 18 volts. The problem is that a nominal 12 volt battery is pretty close to an actual 12 volts - 10.5 to 12.7 volts, depending on state of charge. Under charge, most batteries want from around 13.2 to 14.4 volts to fully charge - quite a bit different than what most panels are designed to put out.
OK, so now we have this neat 130 watt solar panel. Catch #1 is that it is rated at 130 watts at a particular voltage and current. The Kyocera KC-130 is rated at 7.39 amps at 17.6 volts. (7.39 amps times 17.6 volts = 130 watts).
Why 130 Watts does NOT equal 130 watts
Where did my Watts go?
So what happens when you hook up this 130 watt panel to your battery through a regular charge controller?
Your panel puts out 7.4 amps. Your battery is setting at 12 volts under charge: 7.4 amps times 12 volts = 88.8 watts. You lost over 41 watts - but you paid for 130. That 41 watts is not going anywhere, it just is not being produced because there is a poor match between the panel and the battery. With a very low battery, say 10.5 volts, it's even worse - you could be losing as much as 35% (11 volts x 7.4 amps = 81.4 watts. You lost about 48 watts.
One solution you might think of - why not just make panels so that they put out 14 volts or so to match the battery?
Catch #22a is that the panel is rated at 130 watts at full sunlight at a particular temperature (STC - or standard test conditions). If temperature of the solar panel is high, you don't get 17.4 volts. At the temperatures seen in many hot climate areas, you might get under 16 volts. If you started with a 15 volt panel (like some of the so-called "self regulating" panels), you are in trouble, as you won't have enough voltage to put a charge into the battery. Solar panels have to have enough leeway built in to perform under the worst of conditions. The panel will just sit there looking dumb, and your batteries will get even stupider than usual.
Nobody likes a stupid battery.
There is some confusion about the term "tracking":
Panel tracking - this is where the panels are on a mount that follows the sun. The most common are the Zomeworks and Wattsun. These optimize output by following the sun across the sky for maximum sunlight. These typically give you about a 15% increase in winter and up to a 35% increase in summer.
This is just the opposite of the seasonal variation for MPPT controllers. Since panel temperatures are much lower in winter, they put out more power. And winter is usually when you need the most power from your solar panels due to shorter days.
Maximum Power Point Tracking is electronic tracking - usually digital. The charge controller looks at the output of the panels, and compares it to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery. It takes this and converts it to best voltage to get maximum AMPS into the battery. (Remember, it is Amps into the battery that counts). Most modern MPPT's are around 93-97% efficient in the conversion. You typically get a 20 to 45% power gain in winter and 10-15% in summer. Actual gain can vary widely depending weather, temperature, battery state of charge, and other factors.
Grid tie systems are becoming more popular as the price of solar drops and electric rates go up. There are several brands of grid-tie only (that is, no battery) inverters available. All of these have built in MPPT. Efficiency is around 94% to 97% for the MPPT conversion on those.
Here is where the optimization, or maximum power point tracking comes in. Assume your battery is low, at 12 volts. A MPPT takes that 17.6 volts at 7.4 amps and converts it down, so that what the battery gets is now 10.8 amps at 12 volts. Now you still have almost 130 watts, and everyone is happy.
Ideally, for 100% power conversion you would get around 11.3 amps at 11.5 volts, but you have to feed the battery a higher voltage to force the amps in. And this is a simplified explanation - in actual fact the output of the MPPT charge controller might vary continually to adjust for getting the maximum amps into the battery.
Above is a screen shot from the Maui Solar Software "PV-Design Pro" computer program (click on picture for full size image). If you look at the green line, you will see that it has a sharp peak at the upper right - that represents the maximum power point. What an MPPT controller does is "look" for that exact point, then does the voltage/current conversion to change it to exactly what the battery needs. In real life, that peak moves around continuously with changes in light conditions and weather.
A MPPT tracks the maximum power point, which is going to be different from the STC (Standard Test Conditions) rating under almost all situations. Under very cold conditions a 120 watt panel is actually capable of putting over 130+ watts because the power output goes up as panel temperature goes down - but if you don't have some way of tracking that power point, you are going to lose it. On the other hand under very hot conditions, the power drops - you lose power as the temperature goes up. That is why you get less gain in summer.
MPPT's are most effective under these conditions:
Winter, and/or cloudy or hazy days - when the extra power is needed the most.
Ok, so now back to the original question - What is a MPPT?
The Power point tracker is a high frequency DC to DC converter. They take the DC input from the solar panels, change it to high frequency AC, and convert it back down to a different DC voltage and current to exactly match the panels to the batteries. MPPT's operate at very high audio frequencies, usually in the 20-80 kHz range. The advantage of high frequency circuits is that they can be designed with very high efficiency transformers and small components. The design of high frequency circuits can be very tricky because the problems with portions of the circuit "broadcasting" just like a radio transmitter and causing radio and TV interference. Noise isolation and suppression becomes very important.
There are a few non-digital (that is, linear) MPPT's charge controls around. These are much easier and cheaper to build and design than the digital ones. They do improve efficiency somewhat, but overall the efficiency can vary a lot - and we have seen a few lose their "tracking point" and actually get worse. That can happen occasionally if a cloud passed over the panel - the linear circuit searches for the next best point, but then gets too far out on the deep end to find it again when the sun comes out. Thankfully, not many of these around any more.
The power point tracker (and all DC to DC converters) operates by taking the DC input current, changing it to AC, running through a transformer (usually a toroid, a doughnut looking transformer), and then rectifying it back to DC, followed by the output regulator. In most DC to DC converters, this is strictly an electronic process - no real smarts are involved except for some regulation of the output voltage. Charge controllers for solar panels need a lot more smarts as light and temperature conditions vary continuously all day long, and battery voltage changes.
All recent models of digital MPPT controllers available are microprocessor controlled. They know when to adjust the output that it is being sent to the battery, and they actually shut down for a few microseconds and "look" at the solar panel and battery and make any needed adjustments. Although not really new (the Australian company AERL had some as early as 1985), it has been only recently that electronic microprocessors have become cheap enough to be cost effective in smaller systems (less than 1 KW of panel). MPPT charge controls are now manufactured by several companies.
Please email or call us with any question you may have via: Sales@PortableSolarPower.Biz or 1-765-517-1210
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