Solar PV simulator
Design an off-grid or hybrid solar system and watch it run through a day: panels with their I-V curves, PWM and MPPT charge controllers modelled on real products (EPEVER LandStar and Tracer, Renogy Wanderer, Victron SmartSolar), LiFePO4 and lead-acid batteries that charge and drain at their real capacity, DC loads, inverters, grid-tie and hybrid inverters, breakers and fuses. Every part shows its live voltage, current and power, and the parts that are too small for the job burn, trip or sag the way they would on a roof.
Open the labFree, in your browser, no account needed. Part of a free electronics simulator with 293 parts, 193 lessons and 66 builds.
What you can do
- Size a panel array and a battery for a daily load, then prove it on the bench with a day of sun.
- See why a PWM controller wastes the top of a panel's curve and an MPPT does not.
- Wire a 12 V, 24 V or 48 V system with the right cable, fuse and breaker sizes, and find out what happens with the wrong ones.
- Try the solar phone-charging and Wi-Fi vending builds, or a solar floodlight on LiFePO4 cells.
Builds (24)
Solar garden light with dusk switch
Charges by day, lights at night.
Solar phone charger
Panel to USB with a buck converter.
House panel: main breaker and four branch circuits
A 60 A main, four branch breakers, two switched lights, an outlet with a TV and refrigerator, a 1 HP aircon and a 3.5…
14. Solar: the light runs off-grid
Step 14 of the automatic light: The adapter is replaced by PV1 (20 W) → U5 charge controller → BAT1 12 Ah, and the…
Home UPS on a 24 V LiFePO4 battery: charger, inverter, changeover relays, two 220 V outputs
Keeps two 220 V circuits powered through outages from a 24 V LiFePO4 battery; charges from the grid when it returns.
Home UPS on 8 × 3.2 V LiFePO4 cells + BMS: charger, inverter, changeover relays, two 220 V outputs
Keeps two 220 V circuits powered through outages from 8 × 3.2 V LiFePO4 cells; charges from the grid when it returns.
1 HP inverter aircon on a 3.6 kW hybrid at night: what the battery sees
Night-time: no sun, a 24 V 100 Ah LiFePO4 battery feeding a 3.6 kW hybrid, a 1 HP inverter aircon, a refrigerator and…
Why a 1.5 HP non-inverter aircon trips a 3 kW inverter at start-up
A 24 V LiFePO4 battery, a 3 kW pure-sine inverter and a 1.5 HP non-inverter aircon. Switch the aircon on and watch the…
Grid-tie solar in a brownout: why the lights go out even at noon
The grid, a kWh meter and main breaker, a 3 kW grid-tie inverter on four panels, and the house loads. Switch the grid…
Sari-sari store freezer through a brownout: battery, inverter and hours
12 V 100 Ah LiFePO4 battery, 1000 W pure-sine inverter, a chest freezer and two LED bulbs. The panel shows the…
Piso Wi-Fi on solar: how big a panel and battery for a router and coin box
100 W panel, a 10 A MPPT charge controller, a 12 V 30 Ah LiFePO4 battery and the box: router plus coin acceptor on the…
Single 18650 charger with LED charge indicator
Charges one cell from USB; red while charging, blue when full.
18650 battery level indicator
Three LEDs show full, half and low.
Automatic emergency light
LED lamp turns on when mains fails, charges when it returns.
12 V low-voltage battery cutoff
Disconnects the load before the battery is damaged.
10,000 mAh power bank · 4 × 18650
10,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
20,000 mAh power bank · 8 × 18650
20,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
40,000 mAh power bank · 16 × 18650
40,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
10,000 mAh power bank · 2 × 21700
10,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
20,000 mAh power bank · 4 × 21700
20,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
40,000 mAh power bank · 8 × 21700
40,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
12,000 mAh LiFePO4 power bank · 2 × 32700
12,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
24,000 mAh LiFePO4 power bank · 4 × 32700
24,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
42,000 mAh LiFePO4 power bank · 7 × 32700
42,000 mAh, 5 V 2.4 A USB out, 2 A USB charging, full protection.
Lessons (23)
Capstone: solar-powered GPS tracker
Everything together: a solar panel and charge controller keep a LiFePO4 battery up, a buck converter makes 5 V, the…
Charge-pump inverter: a negative rail
No inductor at all: a 555 square wave charges C1 through D1 while its output is high, then, when the output drops…
MPPT: perturb and observe
A solar panel gives its most power at one point on its I–V curve. The ESP32 measures the panel’s voltage and current…
BJT small-signal model (hybrid-π)
For small signals a biased transistor is a resistor r_π between base and emitter and a current source g_m·v_be into…
PWM against MPPT: the harvest, as a number
A PWM controller is a switch: it connects the panel straight to the battery, so the panel runs at battery voltage…
Battery internal resistance
A real battery is an ideal voltage E in series with a small internal resistance r. With no load you read E. Under…
Cells in series and parallel (LiFePO4)
Cells in series add their voltages (and their internal resistances). Cells in parallel keep the same voltage but share…
Li-ion CC/CV charger from an LM317
Li-ion cells must be charged at a limited current (CC) until they reach 4.2 V, then held at that voltage (CV) while…
Cell protection: DW01 + 8205A
Every Li-ion pack has a tiny board that disconnects the cell when it is in danger: over-charged, over-discharged…
Ideal-diode OR-ing: USB plus battery
Two supplies feed one load and must never feed each other. Schottky diodes would waste 0.3 V. Here each supply goes…
The IV curve: Voc, Isc and the knee
A panel is not a voltage source. Open, it shows Voc and gives nothing; shorted, it gives Isc and no volts; the power…
Cold mornings raise Voc; hot noons cut power
Voltage comes from the cells’ temperature, not the sun: Voc falls about 0.3 % for every degree the cells warm, and in…
Shading and bypass diodes: a shadow costs more than its size
A module is three substrings in series, each behind a bypass diode. Shade one third and it cannot carry the string…
A string against the controller: the cold-morning Voc
In series the voltages add, so five 100 W modules make a 112 V string at 25 °C, and 119 V at a 10 °C dawn. A…
Lead-acid against LiFePO4: usable capacity, voltage and life
Two 100 Ah batteries on the same 10 A load. The lead-acid is at 12.0 V and half empty after five hours, where it…
Wiring, fuses and breakers for an array: the 1.25 and 1.56 rules
A PV conductor carries current for hours, and on an edge-of-cloud morning more than the datasheet’s Isc. So the…
Grounding, bonding and surge protection: the two jobs of earth
Earth has two jobs in a solar system. Bonding: every metal frame, rail and enclosure is joined to one equipment…
Commissioning and troubleshooting: the checklist and the fault
Commissioning is the day the installer proves the system: polarity at every string before anything is connected, Voc…
Economics: payback, and what a battery really costs per kWh
A solar system is bought once and paid back by the kWh it replaces: payback = cost ÷ (kWh replaced × tariff). Panels…
Code and safety: PEC 2017 and NEC 690 in one page
The Philippine Electrical Code follows the NEC, and its Article 6.90 is NEC 690: the solar article. Eleven rules carry…
Exam: size and wire a system for this home
A family in Lapu-Lapu: a two-door refrigerator, six LED lights for six hours at night, two fans for ten hours (mostly…
Exam: this system fails on cold mornings
A 24 V system in Baguio: five 100 W modules in one string into a charge controller rated for 100 V input. It works…
Exam: add surge protection and grounding to meet code
A hybrid system on a roof in Cebu, wired and working, with nothing to catch a lightning surge and no earth. Add what…
Parts (10)
Solar panel
100 W · 36-cell mono (12 V nominal) · Voc 22.4 V · Isc 5.75 A · Vmp 18.2 V · Imp 5.5 A · 100 W at…
Small poly panel
Polycrystalline 6 V 2 W mini · 136 × 110 mm · Voc 7.2 V · Isc 0.37 A · epoxy-laminated, bare leads
Solar charge controller
EPEVER Tracer 3210AN · MPPT 30 A · 12/24 V auto · PV max 100 V Voc · load output 30 A · LiFePO4…
Power inverter
Pure sine 1000 W · DC 12 V in · AC 220 V 60 Hz out
Grid-tie inverter
Micro inverter 600 W · MPPT 16–60 V · anti-islanding
Hybrid solar inverter
3.6 kW · 24 V battery · MPPT 60–450 V · Solar → battery → utility
Surge protector (SPD)
PV DC SPD, Type 2, 600 V · DIN-rail module, two pluggable varistor cartridges with a status window…
74xx04 (HC04, DIP-14)
HC04 Hex inverter (NOT) · 74HC · CMOS · DIP-14 · VCC pin 14, GND pin 7
74HC14 Schmitt inverter (DIP-14)
74HC14 hex Schmitt-trigger inverter · 2–6 V · switches high at about 0.55 V_CC rising and low at…
DIN rail (35 mm) (TS35)
TS35 top-hat rail, 300 mm, steel zinc-plated · clip breakers, charge controllers and terminal…
Calculators
Battery runtime calculator
How long a battery runs a load
Solar panel and battery size calculator
Panel watts, battery size and controller current for a daily load
Wire size and voltage drop calculator
Voltage drop in a DC or single-phase run, and the size to use
Also on the lab
Battery and BMS simulator · ESP32 simulator · Arduino simulator · Breadboard simulator · House wiring simulator · PCB layout and perfboard · Brownout backup · Piso Wi-Fi on solar · Questions answered · Compared with other simulators