A 12V solar panel is designed to output at least enough voltage to charge a 12V battery under worst case conditions (low light level, high temperature etc). A 12V battery needs at least 13.6 volts to charge, therefore under worst case conditions a solar panel needs to output at least 13.6 volts.
So, at a minimum, you'll need a 120-watt rated panel to charge your 12V battery within ten hours. Keep in mind that various other factors determine the panel's recharge efficiency. For one, the greater the rated power of the solar panel, the faster you can charge your battery.
Charging your battery at 12 volts and 20 amps will take five hours to charge a 100 amp hour battery. By multiplying 20 amps by 12 volts, 240 watts is how big of a panel you would need, so we'd recommend using a 300w solar panel or 3 100 watt solar panels.
An average 200-watt solar panel will charge a typical 12-volt car battery in 5-8 hours.
If the car was parked at home, you might be able to leave it connected to a battery maintainer, but that's impossible when you're away from a mains socket. Luckily, there is an alternative: a solar panel that can be plugged into the vehicle's diagnostic socket (OBD).
So, at a minimum, you'll need a 120-watt rated panel to charge your 12V battery within ten hours. Keep in mind that various other factors determine the panel's recharge efficiency. For one, the greater the rated power of the solar panel, the faster you can charge your battery.
Solar system sizes and electricity production (average)
Fully charging the 100kWh battery of a Tesla Model X using solar power would require a 25kW solar panels system. That's a whole lot of panels so you'd need a massive roof, not to mention deep pockets!
It is highly recommended that the charge controller be within one meter (approximately 3.25ft) of the battery bank and in the same room or enclosure. Be sure all rooms and enclosures are well ventilated.
The short answer is, in most cases, depending on the size of the battery, it will take around 5 – 8 hours to fully charge a 12-volt car battery with a solar panel that can produce 1 amp of current. For an effective charge, you need to make sure that the panel is directly facing the sun and no obstacles in between.
A solar panel can charge your battery; here is a brief tutorial on getting it set up correctly. Step 1: The first thing you need to do is link your solar charge controller and battery. Ensure the panel is not connected until after you finish your work.
That being said, the average size for a 300W solar panel is around 36 inches by 65 inches. Panels created with DIY solar energy systems in mind tend to be made with aluminum frames and are kept at a lightweight for easy maneuverability.
It's important to understand the following: Don't connect a solar panel directly to a battery. Doing so can damage the battery. Instead, connect both battery and solar panel to a solar charge controller.
You need a 3-6 watt solar panel to maintain a 100Ah lead acid battery.
Summary. You need around 370 watts of solar panels to charge a 12V 120Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
How long does it take to charge a 12V battery with 100-watt solar panels? Here's the short (and generalized) answer: It can take anywhere from 22.8 minutes to 76.8 hours. It's useful to know when the batteries are fully charged to 100%. That's how you know when to stop charging them.
Summary. You would need a 3-5 watt solar panel to maintain the most common sizes of 12V lithium batteries with a PWM charge controller. You would need a 3-4 watt solar panel to maintain the most common sizes of 12V lead acid batteries with a PWM charge controller.
There is a practical limit though, if the solar array is too large then the power is just wasted, since the charge controller is always limiting the output. A typical recommendation is to limit the solar array to 110%-125% of the maximum controller rating.
In short, the answer is yes, solar panels can charge an electric car.
Solar for your home:
A standard solar panel system to cover that usage is 5kW (16 panels) and generates an average of 20 kWh of electricity daily.
Generally, electric cars charged at home use about 7,200 watts (W) of electricity, which can vary depending on the mode and home charger. Most electric car chargers use between 32 and 40 amps, and connect to a 240 volt outlet in your home's breaker box.
You can have multiple sources charging the same battery bank at the same time. Whether it is shore power, an alternator, a generator, solar panels, etc., it doesn't matter. Connect them all. Run them all at the same time.
However, only one charge source should be connected to the battery at one time, as both the BCDC and the Solar Regulator will conflict with each other. If the Solar is disconnected and the vehicle is started the BCDC will see the lower voltage and charge the auxiliary battery accordingly.