How to Charge a 24V Battery System

A reliable 24V battery system is essential for various applications, from off-grid solar setups to backup power solutions in RVs and boats. Knowing the correct charging methods, equipment, and settings for a 24V battery system can extend the battery life and ensure dependable performance.

This guide explores how to charge a 24V battery with different power sources, how many watts you need, and tips for safe and efficient charging practices.

 

 

Overview of Charging Methods for a 24V Battery System

There are three primary methods for charging a 24V battery system: using an AC charger, DC power source, or solar panels. Each option serves different needs and situations.

Charging a 24v battery with AC

AC chargers are commonly used for indoor setups where a stable power source is available. They convert household AC power to the appropriate DC output to charge a 24V system.

Charging a 24v battery with DC

Charging from a DC source, such as an alternator, is ideal for mobile setups (like RVs or boats) where AC power may not be accessible.

Charging a 24v battery with solar panel

Solar charging is increasingly popular for off-grid systems, as it provides a sustainable and eco-friendly power source. With the right setup, solar panels can efficiently charge a 24V battery.

 

How many watt to charge a 24v battery

Understanding the wattage needed to charge a 24V battery is crucial for choosing the right battery charger and achieving efficient charging times. Here, we’ll break down the calculation process using the PowMr 24V 100Ah LiFePO4 battery.

Step1 - Calculate total watt-hours in a 24v battery

To charge the battery fully, we first calculate its capacity in watt-hours (Wh), which is a measure of its total energy storage capacity.

This can be done by multiplying the battery’s voltage (24V) by its amp-hour (Ah) capacity:

• Wh = Battery Voltage(V) × Battery Capacity(Ah)

This result means that you need approximately 2400 watt-hours (24V×100Ah) of energy to fully charge a 24V 100Ah battery.

 

Step2 - Determine the desired charging time

Now that we know the total energy required to charge the battery (2400 Wh), we can calculate the power needed with a specific charging time.

Let’s assume you want to charge the 24V 100Ah battery in 5 hours. To figure out the wattage required, we divide the total watt-hours by the desired charging time:

• Watt = Wh / Hour = 2400Wh/5hours ​= 480W

As a rule of thumb, it is recommended to add a margin of 1.5 to 2 times to account for inefficiencies and energy losses. So, in the case of a 24V 100Ah battery, you will need 720W to 960W to ensures efficient charging.

 

Step3 - Choose the right size of battery charger

While calculating the required wattage is a good starting point, it’s equally important to ensure that the charger’s charging current does not exceed the manufacturer’s recommended limits.

Overcharging or using a charger with excessive current can cause the battery to overheat, which can damage its cells and significantly reduce its lifespan.

To calculate the required charging current, divide the wattage by the battery’s voltage. For example, using 480W for a 24V battery:

• Charging Current= Watt/Volt = 480W​/24V =20A

The 24V 100Ah battery we use has a maximum charging current of 100A, so the 20A calculated here is well within safe limits. This ensures the battery is charged efficiently without risk of damage from excessive current.

Additionally, when charging with solar panels, there’s another consideration: the wattage of the solar panels used does not exceed the maximum input power supported by the charge controller.

 

How to charge a 24v battery with solar panel

After assembling a 24V battery system, you can attach it to the charger. Always ensure that the battery's positive terminal is connected to the charger's positive lead, and the negative terminal to the negative lead.

Charging a 24V battery with a solar panel is a bit more complex and requires extra caution. To make it safer and easier, let's break down the steps for properly charging a 24V battery using a solar panel.

 

How to connect a solar panel to a 24v battery setup

Charging a 24V battery with a solar panel involves connecting the panel to the charge controller, which then connects to the battery.

Please keep in mind that wiring should follow the sequence of Battery > PV Input > Load, to avoid damage and ensure efficient charging.

This ensures that the charge controller correctly regulates the energy coming from the solar panels to the battery. Start by connecting the positive terminal of the battery to the charge controller, then connect the positive terminal of the solar panel to the controller’s PV input. Repeat this process for the negative connections. Always check the system’s compatibility and ensure the charge controller is rated for a 24V setup.

 

How to setup 24v battery charging parameter

When configuring a battery charging system, it's important to choose the correct voltage and current settings based on your battery type (e.g., LiFePO4 or Lead Acid), charger specifications, and the manufacturer's key charging parameters, such as bulk voltage, float charge voltage, overvoltage, overcharge, and the low voltage cut-off value.

For example, with a 24V LiFePO4 battery, maintaining a minimum State of Charge (SOC) of 20% is ideal for longer battery life. Referring to the LiFePO4 voltage chart, the low voltage cut-off would be 25.6V for a 24V system. Ensuring that the battery doesn’t discharge below this voltage helps avoid deep discharge, which can shorten its lifespan.

 

How do you charge a 24v system with 2 batteries

When using multiple batteries, it's essential to consider how they are connected to ensure safe and efficient charging. We will use a system with two batteries as an example. Whether you’re using two 24V batteries in parallel or two 12V batteries in series, the charging parameters will change accordingly.

Two 24v batteries in parallel

In a parallel connection, the voltage remains at 24V, but the capacity (amp-hours) is doubled. For example, a battery system with two 24V 100Ah batteries in parallel would have a total capacity of 200Ah. Since the system now has double the capacity, the charging time will also increase proportionally.

 

Two 12v batteries in series

In a series connection, the voltage adds up, but the capacity remains the same. For example, connecting two 12V 100Ah batteries in series creates a 24V system with the same 100Ah capacity.

You need to ensure that the charging voltage is duplicated based on the specifications of the 12V batteries. However, the charging current should never exceed the recommended value for each individual 12V battery.