Use 24v Solar Panel with 12v Battery

Can you use a 24v Solar Panel with a 12v battery? Absolutely you can.

However, there is a safe way to do that and a way that has more risk of personal injury, fire, and explosion.

If you are wondering which method is best for you, we go over both, so you can make an informed decision about how to proceed.

We also add in some essential information that explains the charging batteries and how that process works.

Is it safe to use a 24v solar panel to charge a 12v battery? It can be!

In this blog, we discuss:

  • How to connect a solar panel to a battery or to a controller
  • The different types of controllers and what they do
  • How to use bare wire connectors when a snap-connector is not available
  • Safely when using solar panels
  • And some essential points to make this project safer and successful

1. What is the Safe Way to Use a Solar Panel to Charge a Battery?

The safest way to charge a battery using a solar panel is also to use a charge controller.

In the case of a 24v solar panel and a 12v battery, the charge controller would limit the amount of energy from the panel to the battery, especially when the battery became nearly fully charged.

Without a charge controller, the battery would continue to receive energy even after the solar panel fully charged the battery. 

As that process continues, the electrolytes within the battery began to heat up until they fail. In the meantime, the battery continues to heat up, and if it were to get hot enough, it would explode and potentially catch fire.

2. What Does a Solar Controller Do?

If you are wondering if you need a solar charge controller, the answer is that you do need one. What a solar controller does is limit or controls the amount of energy that a battery receives.

If a battery receives too much energy, it overcharges. When that happens, the battery heats up, and the electrolytes inside become damaged. 

If the charging continues, the battery can explode or catch fire.

If you use a solar panel to charge your cell phone without a solar controller, then you risk destroying the phone.

Suppose you are storing energy in a solar battery storage system without a solar energy controller. In that case, you risk ruining or shortening the life of the batteries in your battery storage system.

Consider also that the cost of solar batteries for an array is often 1/2 the price of the entire array. Without a solar controller, that is one expensive risk to take.

3. Are There Different Types of Solar Controllers?

Yes, there are different types of solar controllers. 

There are two general types of solar controllers that we see a lot, but in total, there are four types of solar controllers on the market.

The two most frequently used controllers are Pulse Width Modulation or PWM controllers and Maximum Power Point Tracking or MPPT controllers.

There are also Shunt Regulators and Series Regulators. A solar controller is also called a solar regulator. Here is a closer look at what they do.

  • Shunt Controllers or Regulators — The current runs across both the positive and ground terminals. That design gets hot under a load, so you don’t see Shunt Controllers except in solid-state, smaller single panel arrays.
  • Series Regulators or Controllers — is a linear-regulated power supply. They work by changing the voltage requirement or drop between the input and output through resistance. In a solar array, they circulate the current until the battery level drops.
  • Pulse Wave Modulation (PWM) — reduce the amount of energy from the solar array to the battery as the battery becomes full. When the battery charging is complete, the PWM sends a minimal amount of voltage — a trickle — to keep the battery full. Excess energy goes first to the load and then to the batteries. The load is the amount of energy the house or business needs.
  • Maximum Power Point Tracker or MPPT controllers — draw the energy out of the panel or array at the maximum voltage for the batteries or the grid. For a battery, the maximum voltage changes as the battery becomes charged.

You are probably wondering which type of controller you need. The key here is the usage.

Because solar is such a broad spectrum these days, the usage changes. It is difficult to talk about “solar” as an all-encompassing word.

It isn’t all-encompassing because we use solar in so many ways, including:

  • Community-sized solar arrays
  • Home or business solar arrays
  • Mobile solar panels and charging, such as a cell phone charger or a battery backup pack for small devices.
  • Mobile solar panels for automotive applications

The differences in design and how that design meets the needs of consumers change based on each type of application. 

For example, can you use a solar panel charger designed for a hybrid car to charge your cellphone?

Are you able to run a fridge from the power received from a small portable solar panel?

These are how applications change the dynamics of solar power, and those changes open up the usability for the different types of solar controllers.

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4. How Do You Charge a 12v Battery with a 24v Solar Panel?

Instead of connecting the solar panel directly to the battery, you would connect the panel to a solar controller.

Technically, you could use any of the four types of solar controllers.

Still, you’d be much better off using either a PWM or an MPPT solar controller, especially for any application bigger than charging a small gadget.

Step 1 — Connect the solar panel to the controller. Most have snap-together clamps. If not, you will have to wire positive to positive and negative to negative. Be sure the solar panel has a low load before wiring or hire an electrician.

Step 2 — Connect the solar controller to the battery. The controller should have connectors that fit the battery.

Some controllers have ports that hold the bare wire. You can use a ferrule connector if needed. A ferrule is a plated tube the slides over the bare wire to hold multiple strands together.

The ferrule crimps onto the wire, holding it snuggly, and the ferrule’s other end goes into the port on the controller. The controller generally has a screw-type tightener that holds the wire or ferrule in place.

However, many solar panels are plug-and-play, and the wiring snaps together. 

Some older panels may have connections that require physical wiring. Snap the solar panel connector together with the connector to the solar regulator.

Make sure that you deplete the solar panel’s energy load before messing with the wiring.

You can drain a solar panel by connecting it to a lead-acid battery, such as an old car battery.

Power up the solar panel once the components are connected and test the connections using a voltage meter. 

There should be more voltage coming from the panel to the controller than from the controller to the battery.

Safety is always the first part of any electrical job. Ensure that you fully discharge the panel before working on connecting anything to it.

The electrical current can arc, causing severe damage to the panel and the connectors.

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5. How Does a 24v Solar Panel Charge at 12v Battery?

Solar panels produce DC energy, and that is what the battery needs. A 24v solar panel should produce about 18 volts of energy.

The battery will need around 15 volts of energy to charge the battery fully. The panel will vary in voltage depending on how many solar PV cells it has.

A 36-cell panel is ideal since it has about 22v in an open circuit and 18v in a closed circuit. The control will limit the voltage to the battery so that the battery will safely and fully charge. 

Without the controller, the battery would overcharge and cause a potentially dangerous situation where an explosion or fire could occur.

Sources

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