A 12V battery is probably a necessity, whether you’re camping in your RV or boating on the open seas. In order to recharge your RV, van, or boat battery when you go off-grid for an extended period of time and still have enough electricity to run your essential devices, you’ll need a backup power source.
Solar panels allow you to stay off-grid and recharge your 12V battery without shore power.
In order to recharge a 12V battery with photovoltaic (PV) panels, you’ll need all the right components and the know-how for optimizing your solar panels.
Whether you’re off-grid or offshore, this guide will show you how to keep your 12V battery charged using solar panels.
What Size Solar Panel Do You Need to Charge a 12V Battery?
There are many different sizes and rated power outputs of PV solar panels, most of which are compatible with a 12V battery. As well as your energy consumption, the size of your panels will depend primarily on whether or not they match the battery’s amp hours, wattage, and voltage requirements.
Before deciding which size panel is best for charging your 12V battery, ask yourself the following questions:
1.What’s the battery capacity in amp-hour (Ah) rating?
2.How fast do you need the battery charged?
Imagine you own a 12V battery with a 100 Ah capacity and you’re comfortable with a ten-hour charge time.
Firstly, you’ll need to convert the battery’s amp hours into watts. The equation is as follows:
Amp-hours (Ah) x Volts (V) = Watts (Wh)
Keeping with the example above, the formula would look like this:
100Ah x 12 V = 1200 Wh
If you need your battery to recharge fully in 10 hours, you can calculate the following:
Total wattage (Wh) / recharge time in peak sun hours (h) = watts for panel
Plug in the numbers above, and you get:
1200Wh / 10 h = 120 watts
Your 12V battery will need to be charged within ten hours with a 120-watt panel.
A solar panel’s recharge efficiency is determined by a number of factors. For example, the greater its rated power, the faster the battery is able to be charged. As an example, an EcoFlow 400W Rigid Solar Panel with a 23% conversion efficiency rating can charge a 12V battery much faster than a traditional 100W panel.
There are also several factors to consider when choosing a battery. Lithium-ion batteries are more efficient than lead-acid batteries, but they require a higher solar panel wattage. All other factors being equal, you’d need a 120-watt panel for lead acid batteries and a 190-watt panel for lithium batteries.
You may want to consider upgrading to a lithium-ion or LFP battery if your vehicle or boat is more than a decade old and uses a lead-acid battery.
The charge controller you use to connect the solar panel to the battery can also affect how efficiently your solar power system charges.
Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT) are the two main types of charge controllers, with MPPT being the more efficient. With a lithium-ion battery and ten peak sun hours, a 160-watt solar panel with an MPPT charge controller would work better than a 190-watt panel with a PWM.
When you purchase an all-in-one solar power system solution like EcoFlow’s DELTA series, all the necessary components are already included, so you don’t have to worry about compatibility issues. Just plug in the solar panels and you’re good to go.
How Many Solar Panels Do You Need to Charge a 12V Battery?
A standard EcoFlow 100W Flexible Solar Panel is enough to charge most common 12V batteries and is easily affixed to curved surfaces without requiring drilling.
It’s also worth considering a modular power kit that can provide you with enough off-grid electricity to run anything you might need. If you wish to recharge faster or need significant energy output, consider purchasing multiple solar panels.
Components You Need to Charge a 12V Battery
The process of directly charging a 12V battery with photovoltaic panels isn’t as simple as connecting solar panels to the terminals.
To connect the solar panels, you’ll need the following tools and components:
Solar charge controller (must be compatible with 12V batteries; PWM or MPPT)
Charge controller adapter cables
It protects the battery from overcharging, which leads to permanent damage and can even be hazardous, by regulating the electricity flow from the solar panels to it. In order to protect the battery from potential damage, the controller cuts off DC power once it has reached full charge.
In addition to a solar power system, you’ll also need a solar battery to store excess power and an inverter to run AC-powered appliances and devices.
How to Charge a 12V Battery with Solar Panels
The following is a step-by-step guide on how to connect your solar panels to a 12V battery:
Step 1: Your charge controller needs to be connected to the 12V battery
The 12V battery should have wires, so you will need to purchase 10- or 16-gauge wires if it doesn’t. Attach the stripped end of the positive battery wire to the position terminal and vice versa. Insert the bare wire ends into the charge controller ports and tighten them with a screwdriver.
Connect the ring terminal of the positive battery wire to the positive battery terminal. Repeat the process for the negative battery cable.
Step 2: The Charge Controller must be connected to the solar panels
The negative solar panel adapter cable should be attached to the negative solar panel cable. The positive solar panel adapter cable should be attached to the positive solar panel cable.
Connect the positive solar input cable to the positive solar PV terminal on the controller, and tighten the terminal. Repeat this procedure for the negative solar input cable.
With some systems, such as the EcoFlow Portable Solar Panels, you can connect multiple panels in series by using MC4 connectors.
Step 3: Make sure the connection is working
Test the connection by turning on the battery and power system once the wires are connected. Your charge controller should light up, indicating the battery and charge controller are connected. Make sure your charge controller’s display screen is showing readings. If not, you probably didn’t connect everything correctly.
If connecting your solar panels to a power station for charging the 12V battery, you can easily check its connection. Many portable power stations like the EcoFlow DELTA 2 include an MPPT algorithm which tracks the voltage and current rate in real time. Additionally, you may use the dedicated EcoFlow app on your mobile device with an internet or BlueTooth connection to monitor the voltage output and manage the power station. Furthermore, a charge controller will offer updates regarding recharge time.
Step 4: Solar panels should be positioned under direct sunlight
Finally, you will want to position your solar panels for optimal light exposure. You can either mount rigid solar panels on your vehicle or boat’s roof, or you can use the kickstand on your portable solar panels.
If you want to charge a 12V battery, you need a solar panel with a specific wattage, voltage, amp-hour, and energy consumption. If you use a portable power station or solar generator with everything built in, setting up a functioning solar power system between a solar panel and a 12V battery is simple once you know the details.