How to Charge Lithium Ion Battery with Solar Panel

Updated July 10, 2023

Lithium-ion batteries are a great piece of equipment for your solar system since they can be recharged and keep your lights on well after the sun has set. You can use these in many portable electronics.

Lithium batteries can be charged by these solar panels when they lose their charge.

It’s important to know how to charge lithium-ion batteries with a solar panel. It can be quite a tricky process which is why you may need to do some research before doing so.

In this article, we discuss what lithium-ion batteries are and how to charge them safely. We also cover everything that lithium-ion batteries can be used for, and what you need to charge them. 

What Are Lithium Ion Batteries?

A lithium-ion battery is a type of rechargeable battery. It’s charged and discharged by lithium ions that move between the negative and positive electrodes. 

Batteries that can be recharged repeatedly are called secondary batteries. Disposable batteries are called primary batteries.

Lithium-ion batteries are suitable for storing high-capacity power. This is why they are used in various applications. These applications include electronics like smartphones and computers, production equipment, cars, and industrial robots.

Different Types of Lithium Ion Batteries

Lithium-ion batteries are available in many different shapes for various applications. These shapes include:

The rigid plastic case (large threaded terminals)

Small cylindrical (single cell with, a solid body, with no terminals)

Flat or pouch (soft, flat body)

Large cylindrical (single cell, solid body, with threaded terminals)

Other characteristics of Lithium Ion batteries are their Current Capacity and Nominal voltage.

Nominal voltage is the normal voltage that the battery operates at. Some batteries may have a higher voltage when fully charged. 

To further increase the current capacity, you can connect batteries in parallel. However, this process is slightly more complicated than wiring in series. This is because you need to match the internal impedance of each battery.

Can I Charge a Lithium Ion Battery with a Solar Panel?

You can charge a lithium battery with a solar panel. However, the solar panel must have the correct output power requirements to charge the battery. 

The first important factor to keep in mind is potentially overcharging your battery. Lithium-ion batteries damage easily when they are charged beyond their nominal voltage. 

Lithium battery chargers don’t have trickle charging. Instead, the charger stops charging the battery when it has reached its desired voltage to keep the lifespan longer. 

It’s not ideal to connect a solar panel directly to a lithium battery. This is because the solar panel has no way of detecting when to stop giving power to the battery.

It continuously releases energy into the battery whenever it produces electricity from sunlight which results in overcharging and damage to the battery. 

If you connect a solar panel directly to a load, issues could potentially occur. These include:

• The solar panel being overloaded

• The lithium battery not being able to receive maximum power from the solar panel

• Charging the lithium battery is reliant on the weather. Cloudy conditions will not be ideal. 

What Type of Solar Panel can Charge a Lithium Ion Battery?

As long as you use a charge controller then any type of solar panel will charge a lithium-ion battery.

The type of solar panels they can be used with are:

• Flexible solar panels
• Rigid solar panels
• Portable solar panels (briefcase/suitcase)
• Monocrystalline
• Thin-film
• Bifacial solar panels
• Polycrystalline

The wattage of the solar panel doesn’t matter. However, if the solar panel wattage is high then it will charge the lithium-ion battery quickly. The higher the wattage of a solar panel array the faster it will charge a lithium-ion battery bank.

You’ll need to invest in a high-quality charge controller if you want to charge multiple batteries with a single solar panel.

What Do I Need to Charge a Lithium Ion Battery with a Solar Panel?

Solar panels aren’t normally used by themselves to charge a battery. A few components are used in something called a Solar Power System. 

The solar power system is used to power electrical and electronic loads. 

Components of a solar power system include:

• Rechargeable battery
• Solar Panels
• Charge Controller 
• Inverter (AC applications)

If you already have a solar panel and a rechargeable battery then all that you need is a charge controller.

The charge controller prevents the battery from overcharging. It also constantly charges the battery and protects the solar panel from any reverse current. 

Since there are many different types of batteries for solar systems, there are many different types of charge controllers. Each controller is designed to meet the individual needs of each battery type.

You need to buy a solar charge controller that’s specifically designed for lithium batteries. This ensures that the battery stops charging when the nominal voltage is reached.

Charging a Lithium Ion Battery 

Lithium-ion batteries are unique in their charging requirements compared to batteries with different chemistries. There are strict requirements when it comes to charging these batteries. 

The battery charger is a voltage-limiting device. It has differences from other chargers. 

The main differences include:

• It can tolerate tighter voltages

• Higher voltage per cell

• Trickle charging is when a battery charger is capable of charging a fully charged battery. It’s done at a rate equal to its self-discharge rate. This allows the battery to keep its fully charged level.

• Absence of trickle or float charging

The charger comes with certain features to prevent overcharging. These include features such as an end-of-charge detection circuit to keep track of when the battery is fully charged.

Steps to Charge a Lithium Ion Battery

When charging a lithium-ion battery, you need to ramp up the voltage and current followed by a flat voltage and lower amperage.

Step 1: Get the right materials

You need:

• A Solar cell 6V

• 1 x Li-Ion charger board TP4056 (choose a board with 4 outputs. 2 for battery, 2 for connecting the device)

• 1 x Schottky diode

• 1 x Lithium - Ion battery

• 1 x Lithium - Ion battery holder

• 1 x cables

• 1 x solder tools (station, tin, rosin, etc.)

Step 2: Get the Correct Solar Cell

The current from the solar cell can be variable. You can choose a 500 mAh solar cell or a 1 Ah solar cell.

For the Lithium Ion battery, you can choose a solar cell with 5V and 160 mA. ShopSolar.com has a range of 200-watt flexible solar panels at affordable prices.

Step 3: The Circuit

There are positive and negative terminals on solar panels. Connect the positive terminal of the solar cell to the anode of the diode. Connect the negative terminal of the diode to the positive input.

Also, connect the negative terminal of the solar cell to the negative input. Lastly, connect the battery and the positive terminal of the battery to a similar negative terminal.

What Can a Lithium Ion Battery be Used for?

You can use lithium-ion batteries for many things. They can be used for anything from small kitchen appliances to large commercial trucks. They're excellent if you plan on connecting your solar system off-grid.

You also need batteries for solar panels.

The main things that you would use these batteries for are:

• A boat
• A recreational vehicle
• A motorhome
• A camper van
• A caravan
• A trailer
• A yacht
• A holiday cabin
• A shed or a garage

You will need to know how to install solar panels too. For example, installing solar panels on a van.

Do You Need a Solar Charge Controller for a Lithium Ion Battery?

You need a solar charge controller to charge any 12V battery with a solar panel. You also need to take into account the correct size cable for the 12v solar panel. 

A portable generator may be an exception because it should have one built-in and an inverter. 

You may not know how to set up solar panels off the grid. Off-grid residential installations also would need a solar charge controller. 

Your battery is at risk if you charge it without a controller. This will cost you a lot of money. You can potentially damage the cells and destroy the battery. 

Lithium-ion batteries have a battery management system (BMS) to prevent overcharging. You should, however, always have a solar charge controller in your solar setup kit. 

Your lithium-ion battery will be kept safe if you invest in a good quality solar controller. This will make the charging process more efficient.

Key Takeaways

A lithium-ion battery is a rechargeable battery. We now know that these types of batteries come in many different shapes to be used for a variety of different applications.

You can charge a lithium battery with a solar panel but knowing how to do it can be tricky. The solar panel must have the correct output power requirements for the battery to charge.

If you use a charge controller, then any type of solar panel can charge a lithium-ion battery.

You will need certain components to charge a battery with a solar panel. These include a charge controller, solar panels, and a rechargeable battery.

By following the tips and steps in this article, you should have knowledge of how to charge a lithium-ion battery with a solar panel.

Make sure you purchase the right materials and tools. If you have a good solar kit, then charging your lithium-ion battery will be an easy task.

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