How Long To Charge 12V Battery With Solar Panel?

Like it or not, sustainable energy is the way forward. Fossil fuels will run out soon, but we’ll still need to heat our stoves and operate our computers. While there are several renewable sources in development, solar energy is proving to be an economically viable option. Today, a large enough solar panel can power your entire house.

However, you can also use it for smaller, more controlled applications like charging a 12V battery. All you need is a simple charging setup, and a solar panel can charge the battery before you finish the latest season of Stranger Things on Netflix.

Throughout this piece, you’ll get to know how long to charge a 12V battery with a solar panel and use the most efficient setup for it.

What Size of Solar Panel is Best for Charging a 12V Battery?

Size of Solar Panel is Best for Charging a 12V Battery
Size of Solar Panel is Best for Charging a 12V Battery

It depends on what is the total power stored in the battery. You see, voltage is just part of the equation. The full power storage (usually in Ampere-Hours) determines how much energy a battery can store. In the case of multiple batteries connected in parallel, they may have the same voltage but require a lot of currents to charge within a reasonable timeframe.

To preserve the electricity from a solar panel, you must ensure that you check off everything from the list below:

  • A decent-sized solar panel
  • Connection cables
  • Multimeter
  • Charging controller
  • 12V batteries (Preferably Li-ion, but lead-acid will also make do)
  • Inverter

The ideal solar panel size you should go for is a 200-Watt variant, typically 65 x 39 inches (165 x 99 cm). It can charge a 12V car battery within an hour, and you can use it to power other appliances in the house as well. To charge a 100 Ah battery setup, it can take anywhere between 4-6 hours, depending on the weather conditions.

Since solar panels depend on sunshine, you need to run the power supply through a charging controller. It stabilizes the current when charging and comes with an in-built cutoff should you leave the charging battery for too long.

To charge a battery:

  1. Connect the cables to the appropriate points for the charging controller.
  2. Make sure it remains off before you connect the controller to the batteries.
  3. Once you check the connections, turn the charging controller on to complete the circuit and let the battery charge.

Moreover, it would help to use a multimeter to check the flow of current and voltage for the battery to ensure that it is charging adequately.

If you are trying to charge multiple batteries or draw power to other devices from the solar panel, it would be best to use an inverter. It ensures that a DC and AC voltage don’t swap places, and you have electricity just where you want it.

See full this video: How to select and size a solar charge controller

How Long Does a 12V Battery Take to Charge from a 100-Watt Solar Panel?

Despite being around for several decades, solar panels don’t come cheap. While you may not need to spend much on maintenance, the initial cost is still high due to the use of rare earth elements. Yes, alternatives to silicon and germanium are there, but it will take years before solar panels become more accessible than they are today.

As such, you may go for a smaller size of solar panel, say about 100 Watts. The working principle is the same, but this variant generates less power. When trying to charge a fully-drained 12V 100 Ah battery setup, a 100-Watt solar panel needs 5 to 8 hours. Although, charging batteries from zero reduces their usage cycles. So, it is ideal not to let them drain below 50% before you recharge with the solar panels.

In the case of a regular 12V car battery, a 100-Watt solar panel can charge it up in 2-3 hours. You can charge the battery without the use of an inverter, so long as you don’t connect your solar panel to power any AC appliances. Additionally, it is a great idea to use a multimeter to ensure the exact voltage of the battery before charging it.

Can You Use Solar Panels on an RV to Charge a 12V Battery?

The best thing about solar panels is that they are highly versatile. Let’s be honest; you can’t drive your car around with a windmill, can you? Even electric vehicles like the Nissan Leaf and Chevrolet Bolt have solar panels to power systems such as climate control to ease the drain on the primary batteries.

Still, RVs and campervans are the best vehicles to install solar panels. They can provide the electricity you need out in the wilderness without using a drop of petrol. Thanks to their size, you can install high-power solar panels that can efficiently run an HVAC or a refrigerator during the day.

Another way you can utilize those solar panels is to charge the onboard batteries. RVs usually have auxiliary 12V batteries that run additional systems such as the awnings and ambient lights. Depending on the size of your campervan, there are several versions of RV solar panels that you can get. The power output can range from 25 Watts to 150 Watts.


To conclude, it comes down to the exact battery specifications you have. A regular 12V car battery won’t take more than a couple of hours to charge if you have a decent-sized solar panel. On the other hand, high-capacity batteries in the range of 100 Ah can take several hours to charge.

The charging efficiency depends on the weather and time of day as well. It is best to charge the batteries during high noon and with a clear sun to reduce the charging time. Moreover, recharging with a 50% drain is more effective than recharging a dead 12V battery.


  1. What size solar panel to charge a 12V battery
  2. Will a 5W Solar Panel Charge a 12V Battery?
  3. How Long Does It Take A 200W Solar Panel to Charge A 12V Battery?



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