DIY Portable Solar Generator V2

A DIY portable solar generator is an excellent project for individuals who want to harness the power of the sun while also having a reliable source of electricity on the go. You can easily make your portable solar generator with a little knowledge and some basic tools.

Having a portable power source can be invaluable whether camping, traveling, or experiencing a power outage. You may use it to charge your electronics, run small appliances, and even power lights and fans depending on your generator size. The best thing is that you don't have to rely on grid power sources, which may be costly and unpredictable.

Using the sun's power can help you make a clean, long-lasting energy source that doesn't run out. Do-It-Yourself methods also let you make the solar generator fit your needs and your budget perfectly. You can change the size and volume of the battery bank, the number of solar panels, and even add extra ports/outlets as per your own needs.

You will need a Solar panel, a charge controller, a battery bank, and an inverter to make a generator. The solar panels turn sunshine into power, which is subsequently stored in the battery bank. The charge controller ensures that the battery is properly charged and protects it from overcharging. Finally, the inverter transforms the saved DC power to alternating current (AC), allowing you to power different devices and appliances from anywhere.

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Components Used

1. Solar Panel ( TVC Mall )
2. Solar Charge Controller ( Aliexpress )
3. Battery
4. Inverter ( EPEVER )
5. USB-C Socket ( Amazon / Aliexpress )
6. USB -B Socket ( Amazon / Aliexpress )
7. Car Cigarette Lighter Socket ( Amazon / Aliexpress )
8. DC Jack ( Amazon / Aliexpress )
9. AC Outlet ( Amazon / Aliexpress )
10. DC Rocker Switch ( Amazon / Aliexpress)
11. AC Rocker Switch (Amazon / Aliexpress )
12. Heavy duty Rocker Switch ( Amazon / Aliexpress )
13. Battery Capacity Meter Display ( Amazon / Aliexpress)
14. LED ( Amazon / Aliexpress )
15. Wire ( Amazon / Aliexpress )
16. Crimping Terminals ( Amazon / Aliexpress )
17. Cable Lugs ( Amazon / Aliexpress)
18. Heatshrink Tube ( Amazon / Aliexpress )
19. XT-90 terminal ( Amazon / Aliexpress)
20. XT-60 terminal ( Amazon / Aliexpress)
21. DC Fuse Box ( Amazon / Aliexpress )
22. Automotive fuse Holder ( Amazon / Aliexpress)
23. Waterproof Case ( Amazon / Aliexpress)
24. Self-adhesive Velcro ( Amazon / Aliexpress)

Tools Used

1. Cordless Drill ( Amazon )
2. Jig Saw ( Amazon )
3. Deburring Tool ( Amazon )
4. Utility Knife ( Amazon )
5. Cable Stripper ( Amazon )
6. Crimping Tool ( Amazon )

Note: The cost of all the components that I have used is given in the pdf attached. However, the actual cost may vary source to source. The price are based on the Aliexpress listed price.

A solar generator operates by capturing sunlight through solar photovoltaic panels and converting it into electrical power. The functions of each component are mentioned below:

Solar Panel: The solar panel harnesses solar energy and transforms it into direct current (DC) electricity.

Battery: The battery functions as a storage unit for the electrical energy produced by the solar panels, allowing it to be utilized at a later time. It enables you to generate electricity even in the absence of sunlight.

Solar Charge Controller: The charge controller is responsible for regulating the electrical current from the solar panels to the battery. It serves to avoid overcharging and aids in optimizing the charging procedure.

Inverter: The function of the inverter is to transform the direct current (DC) electricity stored in the battery into alternating current (AC) electricity, which is the specific type of electricity utilized by the majority of household equipment.

DC Jack: There are two DC jacks used in this project. The first one is used for Solar panel input and the other one is for DC output. The output DC jack allows you to run devices that are compatible with DC power.

AC Outlet: The AC outlet supplies alternating current to power items that necessitate AC power.

USB Output: The USB output enables the charging or powering of USB-compatible devices, such as smartphones, tablets, or cameras.

Wattmeter: The wattmeter display indicates the amount of power being generated or consumed by the solar generator. Along with that, it shows many other parameters like voltage, current, power, battery capacity, etc.

LED Flashlight: Solar generators often include a built-in LED flashlight, which serves as a practical illumination option for emergencies or outdoor pursuits.

To select the components for a solar generator in a waterproof case, we have to consider the following:

Determine your Energy requirements: Calculate the total wattage or power consumption of the devices you intend to power with the solar generator. This will help you determine the capacity and size of the components you'll need.

Select a Battery: Choose a battery with enough capacity to run the desired appliances for a specific time duration. You have to also select the right battery type (e.g., lithium-ion, lead-acid)

Select a solar panel: Choose a solar panel with the appropriate wattage and efficiency to generate enough power to charge the battery pack.

Select a charge controller: Ensure the charge controller is compatible with the solar panel current and voltage rating

Include an inverter (optional): If you plan to power AC devices, you'll need an inverter to convert the DC power from the battery to AC power. Select an inverter with the appropriate wattage rating for your devices.

Select a waterproof case: Look for a waterproof case that is suitable for your solar generator project. Consider the dimensions of the case to ensure it can accommodate your selected components inside it.

The first step in designing the solar generator is estimating your energy needs. To estimate the energy consumption for the desired devices, we can use the formula:

Energy (in watt-hours) = Power (in watts) x Time (in hours)

Let's calculate the energy consumption for each device:

6W LED for 6 hours: Energy = 6W x 6h = 36 Wh

2W LED for 4 hours: Energy = 2W x 4h = 8Wh

Camera battery of 7.3Wh: The energy consumption is already given as 7.3 Wh

Charging Smartphone battery of 4100mAh: First, we need to convert the milliamp-hours (mAh) to watt-hours (Wh). Energy = (Capacity in mAh x Voltage) / 1000 Energy = (4100mAh x 3.7V) / 1000 = 15.17 Wh.

Laptop for 3 hours: Energy = 65W x 3h = 195Wh

Therefore, the total estimated energy consumption for the above devices is as follows:

6W LED for 6 hours: 36Wh

2W LED for 4 hours: 8 Wh

Camera battery: 7.3 Wh

Smartphone battery: 15.17 Wh

Laptop for 2 hours: 130 Wh

Total Estimated Energy= 196.47 Wh

The preferable battery chemistry for a solar portable generator depends on various factors such as cost, energy density, and lifespan. Lithium Iron Phosphate( LiFePO4) batteries are more suitable for solar generators due to several reasons:

Longer lifespan: LiFePO4 batteries have a significantly longer lifespan compared to other battery chemistries, such as lead-acid or standard lithium-ion batteries. It can last anywhere between 3000 to 5000 charge-discharge cycles.

High energy density: LiFePO4 batteries have a high energy density, meaning they can store a large amount of energy in a compact size ( lightweight ).

Safety: LiFePO4 batteries are known for their excellent safety characteristics.

Efficient charging and discharging: LiFePO4 batteries have a high charge and discharge efficiency.

Note: LiFePO4 batteries may have a higher upfront cost compared to other battery chemistries. If you don't have space and weight constraints, you may think of lead-acid batteries as they are relatively cheaper than this one.

Battery Sizing:

The following factors determine the battery bank size:

1. Daily power consumption

2. System Voltage

3. Depth of Discharge ( DOD )

In our case, we are going to use a 12.8V LiFePo4 battery which has a DoD of 80%

First, let's calculate the usable energy by considering the DoD of 0.8 (80%):

In the previous step, we have estimated the energy requirement is 196.47Wh

Usable Energy = Energy Required / DoD Usable Energy = 196.47 Wh / 0.8 Usable Energy = 245.59 Wh

Next, let's account for the losses of 20%:

Battery Size = Usable Energy / (1 - Losses) Battery Size = 245.59 Wh / (1 - 0.2) Battery Size = 245.59 Wh / 0.8 Battery Size = 306.99 Wh

Therefore, the battery size required is approximately 306.99 Wh.

Battery Capacity (Ah) Required:

Battery Capacity = Battery size in Wh / Battery Voltage = 306.99Wh /12.8V = 23.98Ah

Therefore, the capacity of the battery is approximately 24Ah.

You can easily make your battery pack by using the 32650 LiFePo4 cells and following my guide on DIY-LiFePO4-Battery-Pack

For this project, the requirement is: 12.8 V and 24Ah Battery Pack

Specification of 32650 Cells Used: 3.2V and 6000 mAh

Capacity (mAh):

The desired capacity of the battery pack = 24AH or 24000 mAh.

The capacity of each cell = 6000 mAh

No of cells required for parallel connection = 24000 / 6000 = 4 nos

Commonly cells in parallel are abbreviated in terms of ‘P’, so this pack will be known as a “4P pack”.When 4 cells are connected in parallel, ultimately you make a single cell with higher capacity ( i.e 3.2V, 24000 mAh )

Voltage(Volt) :

The desired nominal voltage of the battery pack is 12.8V.

The nominal voltage of each cell = 3.2 V

No of cells required for series connection = 12.8 /3.2 = 4nos

Commonly cells in series are abbreviated in terms of ‘S’, so this pack will be known as a “4S pack”.

So we have to connect the 4 parallel groups (7 cells in each group ) in series to make the battery pack.

The final pack configuration is designated as a “4S4P pack” with a final specification of 12.8V,24Ah.

The next challenging part is to finding a suitable size of battery pack that can easily accommodate inside the casing. I have used 16 x 32650 Cells, consisting of 2 rows and 8 column form. In this layout, it requires limited space and the weight is evenly distributed in the casing.

Always select a good quality BMS for making the battery pack.

Note: I have used a fuse-protected XT90 connector for the battery terminal.

Solar Panel converts the sunlight into electricity. A specific amount of sun’s energy can be converted to electricity by the solar panel since they are not 100% efficient and they cannot trap the full energy of sunlight. Most solar panels are less than 22% efficient, which means that they can just trap about 22% of sunlight energy. Commonly 3 types of solar panels are used: Monocrystalline, Polycrystalline, and Thin Film.

Monocrystalline solar panels are preferred for solar generators for the following reasons:

Higher efficiency: Monocrystalline solar panels have higher efficiency compared to polycrystalline panels.

Occupy Lesser Space: Monocrystalline solar panels have a higher power output per square foot compared to polycrystalline panels. This means that with limited space available, monocrystalline panels can generate more electricity, making them ideal for applications like portable solar generators.

Better low-light performance: Monocrystalline panels tend to perform better in low-light conditions, such as cloudy or overcast days.

Solar Panel Sizing:

To calculate the size of the solar panel required for a 12.8V/24Ah battery, taking into account 4 hours of peak sun hours you can use the following formula:

Solar Panel Watt = Battery ( WH) / Peak Sun Hour

Panel Watt = 307Wh / 4hrs = 76.75W

You will never get the rated power from the solar panel because there are few losses associated with it like wiring losses and losses associated with converters. Let's consider this loss to be 20%

So the Panel Watt = 76.75W / ( 1- 20% ) = 76.75 /0.8 = 95.93W

Therefore, you would need a solar panel of higher than 95.93W, the most common rating panel available in the market is 100W.

In my case, I am planning to use a lightweight foldable monocrystalline solar panel of 100W.

There are currently two types of charge controllers commonly used in PV power systems :

1. Pulse Width Modulation (PWM) Controller

2. Maximum Power Point Tracking (MPPT) Controller

As the portable solar generator is a small-sized solar system, both PWM and MPPT can be used. However, MPPT charge controllers are preferred because they offer several advantages over the PWM charge controller. One of the main advantages is their ability to efficiently convert and utilize the maximum power available from the solar panels. Additionally, MPPT charge controllers can handle higher input voltages, allowing for the use of longer cable runs and reducing power losses.

Charge Controller Sizing:

Here we have selected a 100W solar panel to charge a 12.8V battery bank.

1. Watt Rating:

The power rating of the panel is 100W

2. Current Rating:

So current = Solar Panel Wattage / Battery Voltage = 100W / 12.8V = 7.8A

3. Consider Safety Margin:

Charge controller rating = Current Rating x Safety Factor = 8.33 x 1.25 = 9.75A

Therefore, the solar charge controller rating is selected nearest the rating available in the market, which is 10A.

Your Solar panels produce DC electricity, which is stored in the battery. If you want to run only DC appliances then you can skip this step. However, If you want to run AC appliances from the solar generator, then an inverter is needed. A solar inverter is a device that converts the stored DC in a battery into AC electricity.

Common Types of Inverters: Modified Sine Wave and Pure Sine Wave

The modified sine wave output is not suitable for certain appliances such as fridges, microwave ovens, sensitive electronic equipment, laser printers, and most types of motors. Generally, modified sine wave inverters work at lower efficiency compared to pure sine wave inverters.

Inverter Sizing:

In my opinion, it is recommended to choose a pure sine wave inverter. The selected inverter has sufficient capacity to handle your intended maximum load in watts.

In my case, the AC appliance that I want to use is a 65W laptop, so by taking some margin, a 150-200W Inverter is sufficient for me. However, I already have a good quality 350W inverter and it fits inside my case. So instead of buying a new one, I used it.

Note: If you want to use a power tool or motor-operated appliance, then you should also consider the Surge Watt rating. Surge watt is the amount of power the inverter can support for a very short time, usually momentary. 

Grab your notepad and vernier caliper, and note down the measurements.

Draw the same-sized shapes on paper, or you can place the components and mark around them.

Cut out the stencils.

If you prefer, you can download the templates that I have made in AutoCAD and print it out.

Note: The stencil is suitable for the component dimensions that I have used. You have to make the cut-out as per your component dimension. It will be recommended to refer the data sheet for correct panel cut-out dimension.

Place the stencils on the desired place of enclosure and fix it at the edges by using glue or masking tape.

For small circular holes, use suitable size drill bits and for bigger size holes, use spade drill bits.

For rectangular cutouts, first drill a few holes at the corner and then use the jig saw to make the exact cutout.

After making the slots, remove the stencils.

To fit the components perfectly, you may need little filing.

Prepare the DC Jack:

• Solder the 14 AWG black wire to the negative (-ve) terminal of the DC Jack.
• Solder the one terminal wire from the fuse holder to the positive (+ve) terminal of the DC Jack.

Mount the DC Jack:

• Insert the DC Jack into the designated cutout in the plastic case.
• Tighten the nut from inside the case to secure the DC Jack in place.

Secure Soldered Joints:

• Use heatshrink tubing to cover the soldered joints on both the negative and positive terminals of the DC Jack.
• Apply heat evenly using a heat gun to shrink the tubing and ensure a tight seal around the soldered joints.

Install Diode:

• Solder the positive leg of the diode to the another terminal wire from the fuse holder
• Solder a piece of red wire to the negative terminal of the diode.
• Use heatshrink tubing to cover the exposed conductive parts of the diode.

Connect XT60 Connector:

• Solder the 14 AWG black wire from the DC Jack to the negative (-) terminal of the XT60 connector.
• Solder the 14 AWG red wire from the fuse holder to the positive (+) terminal of the XT60 connector.

Here I have used crimp terminals instead of direct soldering. Crimping terminals is preferred over soldering because it provides a mechanically secure and reliable connection without the risk of heat damage to sensitive components. Additionally, crimping allows for easier disassembly and rework compared to soldered connections.

You can crimp the terminals by following these simple steps. All you need is a good-quality crimping tool and crimp terminals.

Select the Right Connector: Choose the appropriate crimp connector for your application. The connector should match the wire size and type. Usually the connectors are color coded according to their sizes. I have used yellow terminals for thicker cables and Blue for thin cables.

Strip the Wire: Use wire strippers to remove the insulation from the end of the wire. The length of the exposed wire should be equal to the length of the metal part inside the crimp connector.

Insert the Wire into the Connector: Slide the stripped end of the wire into the crimp connector. Ensure that the wire is fully inserted and that no bare wire extends beyond the connector.

Position the Crimp Connector in the Tool: Place the crimp connector into the appropriate slot in the crimping tool. The tool should have multiple slots for different connector sizes. Make sure to choose the one that matches your connector.

Crimp the Connector: Squeeze the handles of the crimping tool firmly to crimp the connector onto the wire. The tool will compress the metal part of the connector, creating a secure connection.

I have installed a rocker switch with an integrated LED indicator light, intending to use it as the main switch to control all loads connected to battery.

The switch features three terminals: two longer one for load connection and one shorter one for the LED negative terminal.

You can connect the LED in two different method as shown in the above wiring diagram.

All connections were secured with crimp terminals and insulated using heat shrink tubing to prevent short circuits or electrical hazards.

The switch is connected in the positive red wire coming from battery to the fuse box. I have not connected the LED in the rocker switch to save power. However, if you need, use the wiring diagram shown above.

Here I have used a PZEM-015 Digital Battery Monitor to monitor the various parameters of the solar generator. It can monitor the followings:

1. Power: 0-20000W
2. Voltage: 0-200V
3. Current: 0-100A
4. Impedance: 0-1000Ω
5. Internal resistance: 0-999mΩ
6. Capacity: 0-1000AH
7. Energy consumption: 0-9999kWh (Note: 1Wh=0.001kWh=0.001 Kilowatt)
8. SOC: Dump energy is display via the battery symbol, totally 10 grids, every grid present 10% energy

Connection:

It has six terminals: two for external power supply (when the battery voltage is < 8V), two for shunt voltage drop, and two for the battery. In our case, as the battery voltage is always more than 8V, we don't need to connect the external power supply terminals. Therefore, we have to connect the remaining four.

The meter comes with connecting wires with crimp terminals, but in my case, I have used my own suitable connector. You can see the above picture.

To connect the wire to the meter terminal, press the terminal with a screwdriver, insert the wire, and it will be locked in place by pressure.

In this project, I have utilized four DC rocker switches to control the following loads:

Switch 1: Controls the Battery Capacity Meter

Switch 2: Controls the 2 USB Sockets and Car Cigarette Plug

Switch 3: Controls the Output DC jack

Switch 4: Controls the LED flashlight

Each switch is equipped with an inbuilt LED and rated for 12V / 20A. It features three terminals, two of which are silver-colored, and one is golden-colored.

Wiring these switches is straightforward: the two silver terminals are designated for connecting the positive wires of the power source and load, while the golden terminal is for grounding. A wiring diagram provided above illustrates the connections.

To streamline the wiring process, I've prepared a set of black wires with crimp terminals, which loop to connect all four switch ground terminals. Additionally, four red wires with crimped terminals will be connected to the four fuses of the fuse box, and four wires will link to the respective loads. For a clearer understanding of these connections, refer to the accompanying wiring diagram.

Apart from the above 4 DC switches, I have used an additional switch for controlling the inverter. As the inverter external switch port has only two terminals, I have connected only to the two silver terminals of the switch and left out the golden one. Therefore, the LED for this switch is not functional.

This portable solar generator features various DC outputs, including:

• USB Socket-1: 1 x USB-A (QC 3.0) and USB-C PD
• USB Socket-2: 2 x USB-A
• Car Cigarette Plug
• DC Jack

To begin installation, first, mount the two USB sockets and the cigarette plug into their designated cut-outs in the plastic case. Before proceeding to install the DC jack, solder the terminal wires as shown in the above picture.

For ease of wiring, prepare a red and black wire with three crimp terminals each to loop the connections for the USB sockets and cigarette plug.

Connect the red terminal wire to switch-2 and the black wire to the negative terminal of the fuse box.

Note: I have used 3 separate black wire from each socket to the fuse box which is not mandatory. It's worth noting that utilizing three separate black wires from each socket to the fuse box,

Upon further consideration, it became apparent that looping the cigarette plug and DC jack and connecting them to switch-3 for control would be better.

The next idea is to use a DC-DC buck converter to regulate the output voltage to 12V at the DC output. This converter ensures a stable and consistent voltage level, enhancing the reliability and performance.

I have used a 12V/3W LED for flashlight. First solder the terminal wire to the LED and insulate the soldering joint by using heatshrink tubing.

Crimp terminals to the two terminal wires and install it into the cut-out by using silicon glue.

Connect one wire to the switch-4 and black wire to the negative terminal of the fuse box.

The inverter has three terminals for the output AC power designated as L, N, and earth. I have connected a 1.5 sqmm red wire to the L terminal, a black wire to the N terminal, and a green wire to the earth terminal.

The EPEVER inverter used in this project has a port for connecting an external switch. This allows for easy control of the inverter without using the built-in switch.

I have prepared two wires to connect the screw terminal (used for connecting the external switch port ) provided with the inverter and crimp terminals for connecting the switch. You may refer to the above picture for better understanding.

I used Velcro tape to mount heavy components such as the battery, charge controller, inverter, fuse box, and current shunt.

Initially, I installed the cooling fan using silicone glue, but unfortunately, it did not work for me. Later on, I secured it with four nuts and bolts

For solderless wiring, I used XT connectors for the high-current path. The wiring diagram displays the various connectors in this project.

First, I connected the battery meter following the above wiring diagram. Then, I connected all the rocker switches and loads to the fusebox.

Next, I connected the input terminal wires to the fusebox (battery, shunt, and inverter).

After connecting all the terminals, I covered the fusebox.

The next step is to connect the inverter remote switch and three wires from the inverter outlet to the AC socket in the solar generator.

Finally, cross-check to ensure everything is connected correctly.

Connect the XT connectors from the fuse box and solar charge controller battery terminal to the battery XT connector. Then connect the XT connector from the solar input DC jack to the solar charge controller's solar terminal.Here, I have used a T connector for distributing the battery terminal among the load and charge controller.

Charge the Battery:

Connect the solar panel to the input DC jack of the solar generator.

After plugging in the solar panel, observe the solar status LED on the solar charge controller. It will start blinking, indicating that the battery is charging from the solar panel.

Testing:

Turn on the main switch located beside the solar input jack. Then, switch on the battery meter switch. You will notice that the backlight will turn on, displaying the various parameters.

Now, test all the outputs, including USB, DC, AC, and flashlights.

I connected my smartphones to the USB ports and a tablet charger to the AC outlets. Everything works fine as expected.

The fan connection is still pending; I will update it soon.

I hope you enjoyed my project! If you liked it, please consider sharing it with others.Thank You!