DIY Manual DIY Manual Welcome to the MidNite Solar DIY Manual, a new series of instructional material to help our DoIt-Yourself friends. Inside this manual is helpful information on wiring and circuit protection; battery bank sizing and installation; the Classic MPPT charge controller; and overall system design guidance and advice. Read, enjoy, learn! As always, call our Technical Support team with any questions you may have pertaining to your MidNite products.
DIY Manual SYSTEM DESIGN Solar system design involves a load analysis, battery bank sizing, solar panel sizing and configuration, charge controller selection, and inverter considerations and sizing. Proper system design ensures balance between battery capacity and panel charge capabilities via the correct charge controller. An “out of balance” system may not meet your consumption needs, or worse may waste money on unnecessary expenditures.
DIY Manual If the wattage of an appliance is not known or marked on the appliance, use amps. Watts = Volts x Amps. For a 120VAC hair dryer drawing 10A, that will be 1200W (1200W = 120VAC x 10A). Don’t forget the time element: If you use the 1200W hair dryer for 10 minutes, your watt-hours for this appliance will be 200Wh (1200W x 1/6 hour = 200Wh). Refrigerators, freezers, well pumps, et cetera are cyclical loads, turning on and off at random (based on usage).
DIY Manual Panels (or Batteries) in Series – Voltage adds, Current remains the same. Panels (or Batteries) in Parallel – Current adds, Voltage remains the same. For a 50% DOD battery bank, multiply 4500Wh by 2 = 9000Wh. NOTE: What does this mean? You want to consume 4500Wh a day and you want to draw down your bank no more than 50%, so you need a bank that is twice as big. For a 20% DOD bank, multiply 4500Wh by 5 = 22,500Wh. NOTE: Reason for multiplication factor of 5: 100% / 20% = 5.
DIY Manual • • For a 2-string 24V bank, use eight 6V batteries rated at 190Ah: o (6V x 4) + (6V x 4) x 190Ah = 9120Wh For a 3-string 12V bank, buy six 6V, 250Ah batteries: o (6V x 2) + (6V x 2) + (6V x 2) x 250Ah = 9000Wh NOTE: For best battery bank health, avoid more than 3 parallel strings when using flooded or sealed batteries. Too many strings can lead to imbalanced cells due to increased resistance. Most Lithium batteries allow multiple parallel strings. Check with the Li batt manufacturer.
DIY Manual appropriate charge controller, which will determine how the panels are wired together, which will bring us back to how many panels can be wired together, 3 or 4. Step 4 CHARGE CONTROLLER SIZING Charge controllers come in two flavors: Pulse Width Modulated (PWM) and Maximum Power Point Tracking (MPPT). A PWM controller is simple in concept and inexpensive in cost compared to an MPPT controller.
DIY Manual 1. Assume our 250W panel has a Voc of 37V 2. If we round-down and wire 3 panels in series, we get an input voltage of 111V (37V x 3). 3. If we round-up and wire 4 panels in series, the input Voc will be 148V (37V x 4). What is the input voltage limit of your charge controller? If the input limit is 150V, which is common, then you can safely wire up 3 panels in series.
DIY Manual Which Classic is right for you? 150? 200? 250? The Classic’s name refers to the maximum input voltage limit in terms of open-circuit voltage, or Voc. For the Classic 150, the limit is 150V; 200V for the Classic 200, and of course, 250V for the Classic 250. A higher input voltage allows the system to be designed with more PV panels wired in a series string. Remember, voltages add in series and current stays the same.
DIY Manual 1. 96A x 12V = 1152W 2. 1152W / 250W (panel) = 4.6 panels NOTE: In this example, round down to 4 or up to 6 panels. What about the Classic 200 in 24V? 1. 78A x 24V = 1872W 2. 1872W / 250W (panel) = 7.4 panels. Classic Current Output Limits Classic 12V 24V 48V 150 96A 94A 86A 200 79A 78A 78A 250 61A 62A 55A NOTE: Round down to 6 or up to 8.
DIY Manual Another perspective on series strings and Voc … From the preceding discussion of the maximum number of 250W panels using the Classic 150 in 12V, we can use 4.6 panels. Let’s round that up to 5 panels for this discussion. And let’s also assume each panel has a Voc rating of 37V and Isc (short circuit current) of 9A. So, your CL150 in 12V can handle 5 panels.
DIY Manual Step 5 INVERTER SIZING The final step in our system design is to size the inverter to power all your loads. Let’s look again at the Load Analysis Example. Appliance / # Watts Hours TV / 1 75W 4 Hrs 300Wh LED Lights / 3 20W 5 Hrs 300Wh Refrigerator / 1 Toaster Oven / 1 Watt-Hours (Wh) 500W Cyclical 1500Wh 1800W 0.
DIY Manual MIDNITE SIZING TOOL Our Sizing Tool (http://www.midnitesolar.com/sizingTool/displaySizing.php) is a great way to verify your proposed solar system design. Plug into the tool the variables from your PV modules (sticker on the back side of the panel), ambient temp data, battery bank nominal voltage, and how you plan to wire the PV (series and/or parallel), then hit the “Submit Parameters” button. Pay attention to the “Max Voc,” “Array Power (Wattage),” and the “Classics Required” results.
DIY Manual PHOTOVOLTAIC (PV) MODULES A basic solar system consists of solar panels, a charge controller, and batteries. This chapter of the DIY Manual focuses on the solar panels, or photovoltaic modules, or simply PV. Photovoltaic – “Voltage produced by (sun) light.” UNDERSTANDING PV MODULES A solar panel is made of individual silicon cells, wired in series to produce a specific output voltage. Typical panels are made in 60- or 72-cell configurations. 3 types of panels: 1.
DIY Manual information on Voc and sizing the charge controller’s input. Voc is maximum when Isc is at zero. NOTE: Voc will increase in temps below the STC of 77o F, and decrease when temps are above 77o F. In cold climates, Voc may increase to 125% of string voltage, so consider that when designing a system. Refer to the MidNite Classic String Sizing Tool for help … MidNite Solar - Classic Sizing Tool. • • • Vmp – Maximum Power Voltage.
DIY Manual WIRING PV MODULES Solar panels can be wired in series, parallel, or a combination of series and parallel, depending on the desired input voltage to the charge controller.
DIY Manual To wire panels in series, is to connect one panel’s positive wire to the next panel’s negative wire. Positive-to-negative is a series connection, and the individual panel volage adds. Series Connection Example: Voc = 39V; Isc = 9A. If the Voc is 39V, then 2 (in series) x 39V = 78V. The PV string voltage is now 78V, as measured by a multimeter via the string’s positive and negative connections. And the string current remains the same as for one panel (9A per panel, and 9A for the string).
DIY Manual Series & Parallel Connection 117V, 18A 17 | P a g e 10-543-1 REV A
DIY Manual A combination of series/parallel is the most common manner to configure PV arrays when using a charge controller, such as the Classic or KID.
DIY Manual As you can see, selecting and buying PV panels comes last. So, let’s make this work with the new 340W panels you bought! 1. Most PV arrays are about 80% efficient. If you need 8000W of panels, then you actually need 8000W x 1.25 (the inverse of 80%) = 10,000W of PV. 2. 10,000W / 340W = 29 PV panels. 29 is an odd number, so that either goes up to 30, maybe down to 27. Maybe 26. We don’t know yet, so let’s move on for now. 3. The Voc is 42V. The batt bank voltage is 48V.
DIY Manual Conclusion: • • • • 8000W of PV is needed. Take that up to 10,000W for losses. 29 panels are needed. With 3 in series and 5 strings per Classic, round 29 up to 30 panels total. 15 panels per Classic 150. You need two Classic 150s (Use Follow-Me for charge coordination). Selecting the Right Combiner A combiner box is used to combine, or parallel, PV strings together. A combiner electrically combines multiple PV strings and makes one PV output.
DIY Manual PV Combiners “Why You Need a Combiner” Combining (Paralleling) Shown on the right is the MidNite Solar MNPV3 Combiner, configured on the left with 3 circuit breakers and a busbar; and on the right with 2 fuseholders and a busbar. The busbar combines (parallels) the PV strings into one common output. The combiner offers over-current and reverse current protection, to be discussed later, but it also offers a simple and easy manner to combine PV strings.
DIY Manual Paralleling (Combining) Solar panels are wired together in one of three ways: 1) Series; 2) Parallel; 3) Series-parallel combination. Series Circuit 158V, 9.8A 1) Series Circuit: Wire the panels using their attached wires in this fashion … positive-tonegative, positive-to-negative. It’s like a daisy-chain down the string. At the end of the string (left side in the diagram above) is the string’s positive wire; on the right side is the string’s negative wire.
DIY Manual 3) Series-Parallel Circuit: A series-parallel configuration is basically like it sounds … PV panels wired in series, and two or more PV strings wired in parallel. 158V, 9.8A Series-Parallel Circuit 158V, 19.6A 158V, 9.8A To conclude, combining or paralleling is a wiring configuration to join multiple PV panels or strings to create one common electrical output – PV positive and PV negative – while maintaining the string voltage. Remember -- in parallel the voltage stays the same.
DIY Manual Shown are 3 parallel strings, each at 158Voc and 9.8A. String 1 suffered a failure with two PV panels, the string voltage dropped to 79V, and reverse current from Strings 2 and 3 now flows into String 1. Each module has a maximum current rating of 15A; as you can see, String 1 now has 19.6A flowing across it, thus exceeding its max limit.
DIY Manual carry, then friction caused by resistance will raise the wire temperature which eventually leads to failure of the wire’s insulation (the outer protective covering). NEC Article 690.8 requires that a PV conductor be rated at 125% of the PV source current. For example, you want 30A continuous, so you need a wire that can handle 37.5A (125% of 30A). Instead of using #10 AWG rated at 30A, you use a #8 AWG which is rated for 40A.
DIY Manual you want their full wattage! So, you would want to increase the wire size to #10 AWG, which can safely carry up to 30A. Over-Current Protection – Breaker Sizing NEC 690.9 requires that over-current protective devices (breakers, fuses) be rated to handle not less than 125% of the maximum currents. If the over-current protective device is rated for continuous duty (called the 3-Hr Rule), then the amp rating of the device can be at 100% or equal to the maximum currents.
DIY Manual is 24.5A. Therefore, if you elect not to use the combiner, then #6 must be a 30A breaker. If you use the combiner, then #6 can be rated higher than 30A, such as a 40A breaker.
DIY Manual BATTERIES A battery bank can be 1/3 cost (or more) of your solar system, so battery choice is important in terms of budget, longevity, and performance. Considerations when choosing a battery type include cost, voltage and amp-hour capacity of the individual battery and the overall bank, placement in or outside of the dwelling, cold temperatures, charging rates, and future expansion. BATTERY TYPES Flooded – Typical, wet cell battery type; lead plates suspended in electrolyte.
DIY Manual Most Lithium batteries are manufactured with a BMS built-in to the battery itself. Some Lithium batts are simply a bunch of Lithium cells soldered together in series without a BMS. The BMS acts like a “traffic cop” to regulate the individual charging of each Lithium cell in terms of voltage, current, and temperature. Therefore, the BMS needs to be designed for the cells. Avoid a homemade Lithium battery with an over-the-counter, generic BMS.
DIY Manual Proximity – This means physically locating the batteries near associated solar system components, such as the charge controller and inverter, to minimize the length of DC cabling between components. BATTERY CAPACITY Battery capacity refers to the amount of stored energy in your battery bank. In other words, how much energy is available to run your AC or DC loads and for what length of time. The unit of measure for battery capacity (energy storage) is amp-hours.
DIY Manual i. At rest means no charging (solar) or discharging (inverter) ii. Best to wait 30 – 60 mins after last charge or discharge operation. b. Batteries under charge will show a higher voltage than when at rest. i. Batteries need higher voltage during charging to induce current to flow into the batteries. c. Batteries being discharged will show a lower voltage than when at rest. 2. Monitor Your Voltages a. Assume your 12V system was designed for 50% daily DOD. b.
DIY Manual Ending Amps The red arrow above indicates the point during the Absorb cycle at which the current has decreased to its lowest level; that is ending amps, which means the batt bank is full. That is the point that you want the charge controller to transition to Float. As stated, ending amps for most batteries is 1 – 3% of the bank’s 20-Hr, Ah rating. If you want to precisely determine the ending amps for your batteries, then perform the following steps: 1.
DIY Manual Let’s say your Classic is producing 30A into the battery bank, your inverter is consuming 20A, your ending amps is set to 8A, AND you use the internal shunt. The net difference is 10A (30A – 20A) going into the bank but on the Main Status page the Classic displays 30A into the bank, so this may be misleading to you. The 30A shown on the Main Status page needs to decrement to 8A for the Classic to transition to Float. But this may or may not happen due to the demand (outgoing 20A) on the system.
DIY Manual Let’s do some math! Assume you bought a single 12V, 100Ah battery. That gives you 1200Wh (12V x 100Ah) of storage. Let’s next assume that you need to grow your bank 6 months later, and you want 4800Wh of capacity, so you go and buy 3 more batteries. You now have four 12V batteries for a 12V system and your batteries must be wired in parallel making a 4-string bank (See Figure 4). And remember, more than 3 strings are not good (for flooded or sealed batt types).
DIY Manual WIRING THE BATTERY BANK Batteries can be wired in series, parallel, or both, depending on the desired bank’s nominal voltage and the voltage of each individual battery. The battery-based inverter determines the gauge of wire to use to interconnect the batteries into a bank.
DIY Manual “Master” Terminals + + + - - + + + + - - + - - “Master” terminal means the primary connection point on the bank for the positive cable and the negative cable to the inverter and charge controller (and any other direct-connect DC load). See Figures 6 and 7. Figure 7 Conductors carry a specific temperature rating based on the type of insulation used on the conductor.
DIY Manual WIRING & CIRCUIT PROTECTION Wires are used as conductors of electric current. Insulators are material specifically designed not to conduct electricity. When current (amps) flow through the wire, a certain amount of heat is created due to friction caused by the wire’s natural resistance. The greater the amps flowing through the wire, the greater the heat.
DIY Manual Factors which determine the appropriate wire gauge: 1. The anticipated current draw of a load or circuit; 2. The temperature to which the wire is subjected, influenced by a. Ambient temperature, b. If conductor conduit is exposed to direct sunlight, c. Type of wire insulator, and d. Equipment termination temperature rating; 3. Wire rating in terms of voltage and temperature; 4. Derating of wire based on conduit fill (Number of wires in the conduit); and 5. Ambient temperature correction factors.
DIY Manual 3. Reference Figure 6, and 4. #6 AWG wire is correct (Use 15A row, 40’ to 50’). ** NOTE: The 125% multiplication factor is a means to derate the current-carrying capacity of the wire for safety reasons, as explained below. Either you decrease current by 80% OR you oversize wire by 125%. Figure 6 What does this all mean? 1. Let’s assume you have a solar panel with an Isc of 9.2A. 2. The 9.2A rating is determined under standard test conditions. In the real world, the panel can produce more than 9.
DIY Manual ii. In this example, for a PV module with an Isc rating of 9.2A, you need to ensure the wire its connected to has an ampacity rating of at least 14.4A. 5. Lastly, to select the correct sized circuit breaker, follow these two rules: i. If you use a MidNite circuit breaker, the second 125% factor does not apply because our breakers conduct 100% of the rated current continuously. Use a 12A breaker to protect the 11.5A of current flow. ii.
DIY Manual Example – PV system with Voc = 90V, 48V battery bank, 30A PV input that is 50’ from the charge controller. 1. If the highest battery charging voltage is 59.2V, for example, then the MPPT charge controller needs an input minimum of 78.7Voc (59.2V x 133%). 2. A 3% voltage drop with #2 AWG wire means an effective Voc of 87.3V. 3. A 10% voltage drop with #10 AWG wire means an effective Voc of 81V. 4. If the MPPT charge controller needs a minimum of 78.
DIY Manual Figure 10 Figure 9 Our panel mount breakers, the MNEDC series, are NOT polarity sensitive; you can wire either terminal without regard to current flow. Figure 10 shows the terminal lugs of an MNEDC breaker. With this type of connection, ensure you use terminal lugs or ring terminals crimped to the wire.
DIY Manual MidNite breakers are rated for 100% continuous duty and may be opened under a load (that means with current flowing through the breaker). Although the fuseholders are rated at 100% continuous duty, the fuses are NOT. Therefore, the fuseholders CANNOT be opened under a load. Since MidNite fuses are not rated at 100% continuous duty, the fuse must be derated by 80%, or increased by 125%, when sizing for circuit overcurrent protection.
DIY Manual Circuit Breaker Voltage Ratings MidNite circuit breakers are rated at 125V, 150V, 300V, and 600V. Our fuseholders are rated at 1000V and we offer two fuse options: 600V or 1000V (either can be used in the MN fuseholder). NOTE: 600V fuses are available till current stock is depleted; thereafter, only the 1000V fuses will be available. Figure 12 shows a 300V circuit breaker, which are two 150V breakers connected in series via a brass jumper.
DIY Manual Figure 13 Remote Trip Circuit Breaker Figure 14 shows our 175A remote trip breaker, commonly used in rapid system shutdown applications, to secure DC inverter power. MidNite offers the RT breaker in 125A, 175A, and 250A versions. This breaker trips open when 19-24VDC is intentionally applied. The trip voltage is 1/10 of a second in duration; any longer in duration and the shunt trip coil burns out.
DIY Manual CLASSIC CHARGE CONTROLLER This chapter of the DIY Manual explains important characteristics of the Classic charge controller and presents insight and troubleshooting tips gleaned from thousands of Tech Support calls. Please read in junction with the Classic Owner’s Manual for a complete understanding.
DIY Manual This reads as follows … With constant power, if voltage rises, current drops. In this case, power is zero since current is zero: XVoc x 0A = 0W. Isc – Short Circuit Current: With a PV module NOT exposed to sunshine and the positive and negative wires connected to each other, with an ammeter you can measure Isc. When Isc is maximum, the voltage is zero, due to zero resistance in the circuit. This is shown by the power formula: P = V x I.
DIY Manual When designing a solar system, ensure you select the correct Classic controller to handle the maximum current. For example, say you plan to install 4000W of PV and you want to charge a 24V bank. Which Classic should you purchase? Answer – 4000W / 24V = 166.7A. None of the Classics will support this system design. Too much current. You either use two controllers and split the 4000W into two separate PV arrays, or you change the battery bank voltage to 48V: 4000W / 48V = 83A.
DIY Manual Figure 16 Classic Charge Modes: EQ MPPT - Full output trying to get to the Equalize setpoint. EQUALIZE - Has reached the set point and is regulating to maintain voltage. BULK MPPT - Full output trying to get to the Absorb setpoint. ABSORB - Has reached the set point and is regulating to maintain voltage. FLOAT MPPT - Full output trying to get to the Float setpoint. FLOAT - Has reached the set point and is regulating to maintain voltage.
DIY Manual 3. Charge Time = 0.42 x (400 Ah / 65A) = 0.42 x 6.15 hours = 2.6 hours. For the EQ timer, refer to your battery manufacturer specifications. T-Comp There is only one setting in the Classic that can influence a different voltage than what you programmed (i.e., Absorb, Float, or EQ) and that is temperature compensation.
DIY Manual 12V battery = 6 cells; 24V battery = 12 cells; 36V battery = 18 cells; 48V battery = 24 cells EQ (Equalization) EQ is a maintenance mode to equalize flooded lead-acid batteries, and some sealed batteries (Check with battery manufacturer if you have AGM or GEL batteries). EQ is a high voltage setting which basically boils the battery’s electrolyte solution, to remove sulfates that are attached to the battery’s lead plates. EQ Dos & Don’ts • • • Ensure electrolyte solution is full before EQ.
DIY Manual c. Set Float volts = 40V d. Set REBULK = (Voltage you want to start back charging, must be > 40 Volts < 52 Volts 2. The Classic will report BATTERY OVER VOLTAGE and will stop charging (RESTING) until rebulk voltage is reached. Skip Days – This setting forces the Classic in to Float at the start of the charging day vice in to Bulk. Useful if you have an unattended system, say at a remote cabin, one that you do not frequent often, and you do not need the solar system charging fully every day.
DIY Manual DO NOT connect an engine-driven DC generator to the Classic! These will almost always be a constant voltage DC source, which will cause harm to the Classic and void the warranty. Legacy P&O (Perturb and Observe) – To “perturb” means to change.
DIY Manual Is it overcast outside? Panels need sunlight intensity (photons) to create PV current. No current = Resting. PV Input Issue If the PV input voltage drops too low or is absent, the problem probably lies in the PV source circuit; that is, the wiring, disconnects, and circuit breaker(s) on the PV side of the charge controller.
DIY Manual Is the IN voltage 0 on the MNGP? If so check for reverse polarity on the PV input to the Classic. Battery Over-voltage Ensure the Battery voltage is below the Absorb and Float voltage setpoints. If not, do you have another charging source (2nd solar, wind, inverter-charger, or generator) on your battery bank? If so, turn it off until you finish troubleshooting the Classic. Go to the 6th Status page; you will read CLASSIC XXX (i.e., CLASSIC 150) at the top left of the MNGP display.
DIY Manual Classic Will Not Turn On 1. Check Classic-to-battery circuit breaker. 2. Check for reverse polarity of battery positive and negative connections to the Classic. 3. Battery voltage needs to be 10V or higher for the Classic to power up. If less than 10V, charge the battery bank using an external source of power. Classic Stuck Sending Data 1. Check the MNGP firmware (FW) version. The MNGP’s firmware must “match” the Classic’s firmware (i.e., 2133 MNGP matches 2126 Classic).
DIY Manual To reduce AF nuisance tripping: 1. Adjust AF time and sensitivity as per the Classic Owner’s Manual. Power cycle the Classic off then on for these settings to take effect. 2. Consider re-wiring the Classic battery output closer to the batteries. In other words, if the Classic B+ is connected to a battery positive busbar, remove that connection and run the conductor directly to the battery via a circuit breaker.
DIY Manual Got Comm? 1. Boot Jumper installed – This causes the Classic to halt the boot-up process and the MNGP displays GOT COMM? 2. Classic MNGP Port - Can use either the top or middle jacks. If using the middle jack – no updates and will lose green and yellow MNGP LEDs. MNGP Reset 1. Under MISC/MNGP/EXTRAS, type in 1-4-2 and pick YES. 2. If you enter the password in MNGP, that resets the MNGP. 3. If you enable password in Tweaks, that password-protects the entire Classic (same PW used, 1-4-2).
DIY Manual 6. Follow the on-screen prompts to complete the setup. Hard - Hardware factory restore 1. Turn the PV and battery power off to the Classic. 2. Remove the front cover. NOTE: There are 3-4 sets of jumpers directly above the blue terminal block. For our purpose here, we will call the left most jumper “JP1” and the right most “JP4” (actually labeled "Boot"). 3. Locate the 2 jumpers JP1 and JP4. Remove the jumpers and hold in your hand. 4. Turn the battery power on to the Classic. 5.
DIY Manual Figure 17 Notice the orientation of the WBJr purple wire relative to the shunt – the purple wire points toward the battery bank. Very important for the WBJr to be mounted this way; if mounted backwards, your current readings will be inverted. Classic Charge Controller Settings Whiz Bang Jr Status Page 1. Depress Right Soft Key (upper right button) 2. Enter the following data: a. Battery bank amp-hour capacity b. Battery Efficiency 3. Depress Right Soft Key again 4. Enter the following data: a.
DIY Manual 5. Depress Main Menu button to return to previous AUX Menu page 6. Use up/down arrows to ensure WIZBANG JUNIOR reads below the header AUX 2 7. Depress Enter button to save changes Charge Menu 1. Using arrow buttons, highlight Advanced sub-menu, depress Enter button 2. Set Ending Amps based on bank’s amp-hour capacity per battery manufacturer’s guidance. Without guidance, 1% - 3% of total amp-hour capacity is common. 3. Depress Left Soft Key so that SHUNT reads below Ending Amps on MNGP. 4.
