How to Install a Mini Solar System | Panels, Battery, Inverter

Fix a 100W panel at a 30-degree angle facing south, first connect the controller to the 12V cell, then connect the 300W inverter to convert to 220V AC power. Three steps can complete an efficient assembly of a micro system.

Panels

Pick panels

On the market's 100W monocrystalline silicon solar panels physical dimensions mostly are 1,195 mm long, 540 mm wide, 30 mm thick, single piece weight fluctuates between 7.2 kg to 7.5 kg. Monocrystalline silicon's panel photoelectric conversion rate can maintain in the 21% to 22.5% range, compared to polycrystalline silicon panel's 15% to 17% conversion rate, which is higher by 5 percentage points. Each nominal 12V 100W panel, the back's factory nameplate will indicate the open circuit voltage (Voc) is 22.5V, the optimal operating voltage (Vmp) is 18.0V, the short circuit current (Isc) is 5.8A, and the optimal operating current (Imp) is 5.55A. Install two pieces of 100W panels, can provide 200W peak output power.

Monocrystalline silicon panels outdoors run 10 years after, output power will decay about 10%, reach 25 years node time, still can maintain 80% of initial rated power. Use multimeter's DC 200V gear, in the morning 11 o'clock to afternoon 1 o'clock cloudless weather under test panel positive negative two ends, reading in the 21V to 22V range belongs to the normal factory standard.

Calculate tilt angle

Solar panel's power generation efficiency highly depends on sunlight incident angle, needs panel's orientation to align due south (southern hemisphere) then align due north, angle deviation controlled within plus minus 5 degrees. Panel's tilt angle (elevation angle) should according to installation location's latitude proceed setting, spring and autumn's panel tilt angle equals local latitude value, summer due to sun elevation angle becomes large, tilt angle should adjust to latitude value minus 15 degrees, winter then adjust to latitude value plus 15 degrees.

· In the north latitude 40 degrees region, summer's ideal installation tilt angle is 25 degrees, winter needs to be raised to 55 degrees.

· Adopt fixed bracket not make any angle adjustment, whole year fixed at 40 degrees tilt angle, will cause winter sunshine power generation amount loss 12% to 15%.

· Every day's effective sunshine time (Peak Sun Hours) is usually between 3.5 hours and 5.5 hours, 200W array under 4 hours effective sunshine, one day produces 0.8 degree electricity (800 watt-hours).

Leave gap

Panel at work time surface temperature will significantly rise, summer sunlight exposure under, panel surface temperature can reach 65 degrees Celsius to 70 degrees Celsius. Solar panel's temperature coefficient is usually -0.38%/℃, temperature every exceeds 25 degrees Celsius standard test condition 1 degree, output power will then drop 0.38%. When the panel temperature reaches 65 degrees, power loss as high as 15.2%, originally 100W panel actual output only remains 84.8W. Install on roof or RV top, must use height is 50 mm to 70 mm Z-shaped aluminum alloy bracket.

· Panel backplate and installation plane between at least must keep 40 mm ventilation gap, bottom air convection can surface temperature reduce 8 degrees to 12 degrees, recover about 3% to 4.5% power loss.

· Each Z-shaped bracket needs use M6 specification 1/4 inch stainless steel bolt penetrate frame reserved 8 mm oval hole proceed fixing, tightening torque needs reach 12 Newton meters (Nm).

· One set of 4 brackets cooperate anti-loose nut, can bear 2400 Pascals (Pa) wind load and 5400 Pascals snow load.

Match cables

The original factory usually brings the length is 90 cm, wire diameter is 4 square mm (12 AWG) pure copper tinned cable, and at the end crimped MC4 male female plugs. MC4 connector's shell protection level reached IP67, can block moisture invasion underwater at 1 meter depth for as long as 30 minutes. Connector interior contact resistance must be less than 0.5 milliohms, prevent 5A to 10A current continuously passing through time produce heating melting phenomenon.

Connect solar panel to distance 5 meters away charge controller time, cable total length increased 10 meters (positive negative pole one comes one goes), in order to 18V direct current transmission process in voltage drop (Voltage Drop) control at 3% (about 0.54 V) within, must extension wire's wire diameter upgrade to 6 square mm (10 AWG). Cable outer skin needs carry UV-resistant (ultraviolet) mark, in minus 40 degrees Celsius to above zero 90 degrees Celsius extreme temperature difference environment, prevent rubber insulation layer in 3 years within happen embrittlement and cracking.

Series parallel connection

System expansion to 200W or 300W, connection method divided into series and parallel two types. Two pieces 18V 5.5A panels series connect, need to first piece's MC4 positive pole insert second piece's MC4 negative pole, total output voltage will superimpose to 36V, total current maintain 5.5A unchanged. The series method can greatly reduce cable loss, 36V voltage under the same wire diameter voltage drop compared to 18V lower 50%. Two pieces panels parallel connect, need buy 1 pair Y-shaped MC4 branch connectors, to two panels' positive poles connect together, negative poles connect together. This time, the total voltage remains at 18 V, and the total current doubles to 11 A.

· Parallel array at meet partial shadow shading time power generation performance better, when among them one piece panel is by leaves shaded 10% area, single panel's power output will drop 50% even if the bypass diode (Bypass Diode) is complete open circuit.

· Adopt parallel connection method, another piece of not shaded panel can still full speed output 5.5A current.

· Adopt series connection method, one piece panel is shaded, produced high resistance will stick entire circuit's current flow, lead to entire 200W array's output sudden drop to 10W below.

Battery

Choose which kind of cell

One piece 12V 100Ah AGM lead-acid cell weight reaches 28 kg to 32 kg, equivalent capacity lithium iron phosphate cell weight only is 11 kg to 12 kg. Lead-acid cell's nominal cycle life at depth of discharge (DoD) is 50% condition under usually is 300 times to 500 times, long-term discharge exceeds rated capacity's 80%, its internal lead plates will in 3 to 6 months within happen irreversible sulfation, lead to total capacity permanently shrinking 40% above.

Lithium iron phosphate cell at 80% depth of discharge under, cycle charge discharge times can reach 3000 times to 5000 times. Continuous use 7 years (according to every day charge discharge 1 cycle calculate), actual retained capacity still can maintain at factory rated value's 80% above.

Discharge process in voltage smoothness has obvious difference, lead-acid cell at release 50 ampere-hours electricity after, terminal voltage will drop from full charge's 12.9V to 11.8V around, lithium iron phosphate cell at release 90 ampere-hours electricity before, terminal voltage always maintain in 12.8V to 13.2V range.

Calculate how much electricity

One piece nominal is 12.8V 100Ah lithium iron phosphate cell, theoretical electricity storage is 1280 watt-hours (Wh), is 1.28 degrees electricity. Limited by internal physical chemical reactions' limitation, the daily safe discharge range is 10% to 100%, actual callable energy is 1152 watt-hours. Through inverter convert to 110V or 220V AC power, the inverter will produce 8% to 15% heat loss, finally, the socket end output effective electricity is roughly 970 watt-hours to 1030 watt-hours. According to power calculation, it can support one rated power 45W portable car refrigerator continuous compression cooling 22 hours, or let one 65W laptop run full load for 15 hours.

In terms of discharge rate, lead-acid cells exist Peukert's effect (Peukert's Law), with 100A large current (1C discharge rate) force discharge, the actual released total electricity will sharply reduce from 100Ah to 55Ah to 60Ah. Lithium iron phosphate cell not affected by this effect interference, with 10A (0.1C) slow discharge, or with 100A (1C) fast discharge, all can stably release 95Ah above true capacity.

Match thick wires

Connect cell end to 1,000W pure sine wave inverter, direct current loop in current load extremely large. Inverter full load output 1,000W AC power time, add 10% conversion loss, cell end needs continuous output of about 1,100W DC power, at 12.8V voltage under actual continuous current reached 85.9A. Start carrying AC motor appliances, inverter output power instantly soars to 2000W peak time, cell terminal end's transient current will break through 170A.

Deal with high intensity load, cell and inverter between connection wire must use cross-sectional area at least is 21.1 square mm (4 AWG) pure copper soft silicone wire, cable length exceeds 1.5 meters, wire diameter needs increase to 33.6 square mm (2 AWG), ensure line loss voltage drop lower than 0.2 V.

Copper wire's insulation outer skin needs to possess a 105 degrees Celsius high temperature tolerance level. The two ends need to use hydraulic crimping pliers to apply at least 8 tons of pressure, crimp M8 specification red copper tinned cold pressed terminals, and put on heat shrink tube. Fixed on cell copper terminal post's stainless steel nut, must use a torque wrench to apply 10 Newton meters to 14 Newton meters torque screw dead, loose contact surface will make contact resistance from 0.1 milliohms soar to 50 milliohms, at 85A current pass through time produce 360W severe heating.

Look protection board parameters

BMS factory set single cell overcharge protection voltage is 3.65V, whole piece 12V cell (composed of 4 series single cells) overcharge cut-off voltage usually set at 14.6V, charging voltage reaches this value, BMS inside MOSFET switch will in 50 milliseconds within disconnect charging loop. Over-discharge cut-off voltage set at 10.0V to 10.4V between, prevents cell electricity being pumped dry.

One piece standard match 100A BMS cell, allowed continuous maximum charge discharge current both are 100A, appliance start instant, BMS allow pass through 200A surge current continuous time only is 3 seconds to 5 seconds, exceed 5 seconds then will trigger overcurrent protection mechanism, cut off output. Happen positive negative pole physical short circuit extreme situation under, BMS short circuit protection response time needs less than 250 microseconds, rapidly pinch off as high as 1000A above short circuit transient current, prevent cell internal temperature exceed 150 degrees Celsius lead to separator thermal melting perforation.

Don't freeze charge

Lithium iron phosphate's discharge temperature range is from minus 20 degrees Celsius to above zero 60 degrees Celsius. At minus 10 degrees Celsius, the internal electrolyte viscosity increases, ion conductivity drops, the cell's internal resistance will increase 2 to 3 times, and the maximum available capacity will shrink from 100 Ah to 70 Ah around. Charging temperature's limitation more strict, absolutely prohibit in 0 degrees Celsius (freezing point) below physical environment in toward lithium iron phosphate cell input charging current.

Lower than 0 degrees Celsius time forcibly with 10A above current charge, lithium ions unable embed graphite negative pole's crystal lattice in, will at negative pole surface deposit into metal lithium dendrites (Lithium Plating). Growing dendrites will with every day 0.1 mm to 0.5 mm speed pierce through 15 micrometers thick polyethylene separator, cause cell internal physical micro short circuit, make cell in 10 to 20 charge discharge cycles completely scrapped.

Low temperature environment used cell must possess BMS low temperature cut-off function, or at cell outer layer wrap one layer power is 30W to 50W silicone heating film, environment temperature lower than 5 degrees Celsius time, system will first utilize solar panel provided 3A to 5A current to give heating film supply power, to cell physical temperature pull up to 5 degrees Celsius above, BMS will only release main charging loop.

Inverter

Buy which kind of waveform

On the market, nominal 1,000W inverters are divided into modified sine wave and pure sine wave two kinds. The former's price is usually between 40 US dollars and 60 US dollars, and the latter's selling price often resides in the 120 US dollars to 180 US dollars range. Modified wave inverter outputted AC power is a kind of stepped square wave, its total harmonic distortion rate (THD) often exceeds 20%, will lead to carry AC motor appliances operation temperature rise 10 degrees Celsius to 20 degrees Celsius.

The rated power is 60W AC electric fan supply power, use a modified wave inverter will produce continuous 50 hertz buzzing AC sound, and in continuous run 3 hours, the fan motor's coil life will shrink by about 15%. Pure sine wave inverter able output THD less than 3% smooth curve voltage, at drive one 700W microwave oven or one 150W LED TV, can electrical energy conversion's reactive loss press down at 5% scale line within.

The inverter's internal conversion efficiency is not a fixed percentage value. When a 1,000W pure sine wave inverter only drives one 10W LED bulb, its work load rate is only 1%, electrical energy conversion efficiency will plummet to 60% trough value; plug in 300W to 700W appliances, make load rate maintain in 30% to 70% range within, machine then can run out 90% to 93% highest nominal efficiency peak.

Leave enough margin

One nominal cooling power is 80W single door small refrigerator, its internal compressor at start instant's initial 20 milliseconds to 50 milliseconds range within, needs to draw rated current 5 to 7 times starting inrush current. This 80W refrigerator at start that 0.05 seconds within, will toward inverter demand 400W to 560W transient peak power. One qualified 1,000W continuous output inverter, its internal capacitors and MOS tube array possess a bear 2000W peak power for as long as 10 milliseconds physical carrying capacity.

Output end plugged in appliances total power reached 1,100W (overload 10%), inverter's overload protection circuit will trigger at about 60 seconds and cut off 110V or 230V AC output; instantaneously plugged in 1500W heavy load (overload 50%), protection chip will in 2 seconds to 3 seconds within forcibly blow internal 30A fuse.

Carry broadband control's inverter at input end DC voltage drop to 10.5V time will emit frequency is 1Hz low voltage alarm sound, cell end voltage continues to drop and touch 9.8V to 10.0V absolute low voltage red line, inverter will in 0.1 seconds time within thoroughly close AC output, prevent 12V lead-acid cell's remaining electricity from 20% thoroughly pump dry to 0%.

Don't ignore no-load

Inverter as long as the fuselage is opened, the power toggle switch, even if the AC socket is not plugged in, the machine's internal standby circuit and step-up transformer will still consume 0.6A to 1.2A direct current. With an average 0.8A no-load current to calculate, let the inverter standby run 24 hours, it will from a 12V cell system in vain consume off 19.2Ah electricity.

In vain lost 19.2Ah capacity, occupied one piece 100Ah lithium iron phosphate cell total available energy (about 90Ah)'s 21.3%, according to proportion equivalent to out of thin air evaporated exceeded one fifth reserve electricity. Carry energy-saving mode's advanced inverter, can through every 2 seconds toward socket send one time duration 16 milliseconds AC pulse to detect load, continuous 10 minutes within not detected greater than 15W appliance plug in, machine will to own standby current forcibly press down to 0.15A to 0.2A extremely low level.

Inverter shell's two pieces 60 mm diameter high-speed cooling fans usually will not turn on time immediately rotate, chassis internal aluminum cooling fins temperature broke through 45 degrees Celsius, or output load rate exceeded 30% (reached 300W output power), temperature control switch then will toward fans deliver 12V driving voltage, make them with per minute 2500 revolutions to 3000 revolutions rate draw about 40 cubic meters of cold air per hour.

Don't pull too long a wire

Convey 12V system's cell DC power to inverter input end time, 2 roots pure copper cables' total length every increases 1 meter, circuit's physical resistance will then increase about 0.005 ohms. Inverter full load draw 85A direct current time, mere 0.005 ohms resistance will produce 0.425V voltage drop, at the same time on cable surface convert to 36.1W useless waste heat. Battery ends 12.8V voltage drops to 12.3V below and arrives at inverter port, its internal step-up transformer forced to input end's work duty cycle raise to 85% above, leading to overall DC to AC efficiency sudden drop about 7 percentage points.

To 100 A large current in transmission process, voltage drop loss control in 2% (about 0.24 V) allowable standard within, cell terminal post to inverter backplate terminal between physical distance must strictly be controlled in 1.5 meters within, cross-sectional area up to 21.1 square mm (4 AWG specification) cable's bending radius must not be less than its diameter's 6 times, prevent internal 300 roots to 500 roots fine copper wires from breaking under extreme bending exceed 5% proportion.

Grounding prevents electric shock

Install inverter fuselage time, casing back reserved M4 specification grounding bolt must tightly crimp one root cross-sectional area not less than 8 square mm (8 AWG) yellow green two-color pure copper grounding wire. One root, about 1.5 meters to 2 meters, grounding conductor needs to use screw fasten on metal chassis or bury underground deep up to 1.2 meters galvanized grounding round steel on. Ensure the entire grounding loop's overall resistance value is less than 0.1 ohms, internal 110V AC live wire because insulation skin broken contact to aluminum alloy shell, time, up to 15A above short circuit current then can import to earth in 50 milliseconds.

Connect cell end positive negative pole's at that moment, the inverter's internal input end large capacity capacitor will instantly flood with up to 150A initial charging current, leading to metal terminal post surface producing up to 2000 degrees Celsius tiny electric spark. At 100Ah cell positive pole and 1,000W inverter positive pole connection line between series connect one calibrated amperage is 100A ceramic fuse, or install one can in 0.05 seconds within automatically trip direct current 120A air switch, can to entire set system circuit catch fire probability compress 98% above.