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An RV roof with panels waiting to be joined and cables with nowhere to plug in is the moment a solar panel diagram stops being a picture and starts being a plan. A solar panel diagram shows how the parts of a solar power system connect: panels to controller, controller to battery, battery to inverter, and inverter to the loads that use the power. This guide reads a diagram step by step, using figures from kit listings where a number is needed.
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The quick answer
Read a solar panel diagram from the sun to the loads: panels make the power, the controller manages it, the battery stores it, and the inverter turns it into the power the loads use. The panels connect to the controller, the controller connects to the battery, and the battery connects to the inverter. Once that chain is clear, the rest of the diagram is detail: cable sizes and the loads at the end. The sections below follow the chain in order, with figures from kit listings.
Step 1: Start at the panels
The panels sit at the start of every diagram, and their figures set the size of the rest of the system. A SOLPERK listing states a 30W panel for 12V batteries, with a cell efficiency of 30%, while a Topsolar listing states a 100W panel for 12V battery charging, with a cell efficiency of 19.5%. An ExpertPower listing states six 100W panels for a 600W array. Panel wattage is the figure the controller and the battery have to match, so read it first and write it down before moving on.
| Reference kit | Panels | Controller | Battery |
|---|---|---|---|
| SOLPERK 30W MPPT Kit | 30W, 12V | MPPT | 12V maintainer |
| Topsolar 100W Kit | 100W, 12V | 30A PWM, 12V/24V | 12V charging |
| ExpertPower 5KWH Kit | 600W, 6 x 100W | 40A MPPT | 12V 100Ah LiFePO4 |
Panels also carry the weather figures: the SOLPERK and Topsolar listings state wind pressure of 2400Pa and snow loads of 5400Pa. Those figures belong to the mounting, not the wiring, but they sit on the same diagram, so check them against the roof or the rack the panels will sit on.
Step 2: Follow the wire to the controller
The controller sits between the panels and the battery, and the diagram shows it as the box the panel wires run into. A Topsolar listing states a 30A charge controller for 12V or 24V systems, while an ExpertPower listing states a 40A MPPT controller. The controller’s job is to keep the battery from overcharging, and the SOLPERK listing states protection against overcharge, over-discharge, short circuit and reverse polarity. The controller also carries indicator lights: the SOLPERK listing states 3 indicator lights, blue for the panel connection, red for charging and green for a full battery.
Check the controller’s current figure against the panels: a Topsolar listing states the system can expand to a maximum of 260W on a 12V system or 520W on a 24V system. The controller figure has to cover the panels that feed it, so compare the figures before the diagram is drawn.
Step 3: Follow the controller to the battery
The battery sits after the controller on the diagram, and it stores the power the panels make. An ExpertPower listing states a 12V 100Ah LiFePO4 battery, with 4 batteries in the kit, and states the pack gives 2500 to 7000 cycles with a 10 year lifetime. The SOLPERK listing states its kit is designed to charge and maintain 12V batteries, including LiFePO4, and states its panel has a lifespan of up to 25 years. Battery capacity is given in amp-hours, and the diagram shows the battery as the block the controller feeds and the inverter draws from.
The battery also sets the system voltage: an ExpertPower listing states the batteries can expand in series at 48V 100Ah or in parallel at 12V 1000Ah. Series raises the voltage while parallel raises the capacity, so the diagram has to show which way the batteries are joined. See the series vs parallel solar panels guide for how series and parallel differ.
Step 4: Follow the battery to the inverter and the loads
The inverter sits after the battery on the diagram, and it turns battery power into the power the loads use. An ExpertPower listing states a 3KW pure sine wave inverter charger with a 60A charger, and states it swaps between shore power and battery power in 5ms. The inverter also carries a low-temperature cut off: the same listing states charging stops below 23°F (-5°C). Loads sit at the end of the diagram, and the inverter figure has to cover them: the ExpertPower listing states a 30A DC-DC charger alongside the inverter, so the diagram shows both charging paths into the battery.
Cables join the blocks: the ExpertPower listing states one pair of 20ft 10AWG cables from panel to controller and one pair of 6ft 8AWG cables from controller to battery. Cable gauge is part of the diagram, so read the gauge the listing states and keep it on the drawing.
Ways to read a solar panel diagram without getting lost
- Start at the panels and follow one wire at a time to the loads, instead of reading the whole diagram at once.
- Write the figures next to each block: panel watts, controller amps, battery amp-hours and inverter watts, using the figures the listings state.
- Check the cable gauges on the drawing: the ExpertPower listing states 10AWG cables from panel to controller and 8AWG cables from controller to battery.
- Watch for figures that disagree: the Topsolar listing states a weight of 15.84 pounds in the bullets and 15.21 pounds in the spec table, so trust the bullets where they disagree.
FAQ: power away from the grid
What does a solar panel diagram show?
It shows how panels, controller, battery and inverter connect, and where the power flows. The panels feed the controller, the controller feeds the battery, and the battery feeds the inverter and the loads.
What is the difference between series and parallel wiring?
In series, panels join in a chain and the voltages add; in parallel, panels join side by side and the currents add. An ExpertPower listing states its batteries can expand in series at 48V 100Ah or in parallel at 12V 1000Ah, which shows the same idea for batteries.
How big should the controller be?
The controller figure has to cover the panels that feed it. A Topsolar listing states a 30A controller for a 100W panel kit that can expand to 260W on 12V or 520W on 24V, and an ExpertPower listing states a 40A MPPT controller for a 600W array. Check the controller figure against the panels it will serve.
Do I need an inverter in a solar diagram?
Yes, if the loads need household AC power. An ExpertPower listing states a 3KW pure sine wave inverter charger, which turns battery power into AC for the loads. A system that only charges 12V batteries needs no inverter, and the SOLPERK listing states its kit is a 12V battery maintainer with no inverter listed.
Related solar guides
See the series vs parallel solar panels guide, the wiring solar panels in series guide, the solar panel wiring connectors guide and the solar panels guides.
