How to Charge a Leisure Battery?

‘How to charge a leisure battery?’ seems like an easy-to-answer question. However, while charging a leisure battery isn’t at all difficult, many caravan and motorhome owners tend to follow the wrong charging habits. The end result is that the battery hardly ever meets its intended lifespan and gives up midway, even when you are on the road.

This article will detail the recommended process to follow while charging a leisure battery, along with answering all the relevant doubts that users often ask.

What is a Leisure Battery?

A leisure battery is a battery inside a motorhome or a caravan that powers all the appliances within. This battery usually runs on 12V, and should not be confused with a vehicle’s starter battery. The purpose of the starter battery is to provide a surge of current when the vehicle is started. However, a leisure battery provides a moderate current constantly for the electric equipment present inside the motorhome.

There are many different types of leisure batteries in the market. Conventional battery technologies such as gel and AGM are lead-acid batteries that have a low lifespan and several other drawbacks. Therefore, most caravans and motorhome’s leisure battery nowadays is a variation of lithium-based batteries, most popularly the LiFePO4.

How to Charge a Leisure Battery?

Charging a leisure battery is not a one-size fits all phenomenon. There are multiple ways to charge a leisure battery, and different types of batteries require varying ways of charging. The three most common battery charging methods are:

Charging Through Split Charge Relay

A split charge relay is one of the most popular leisure battery charging methods. This method involves connecting the battery charging circuit to the engine-driven alternator. This means that when the engine is switched on, the battery goes into charging mode.

This method has further subtypes, which are:

1. Ignition-Triggered Relay: An ignition-triggered relay is a simple circuit where the battery starts charging whenever the engine is switched on, usually on a 12 V DC signal. This is not a recommended charging method as there is no proper voltage compatibility with the particular battery you are using. Additionally, there is a good chance that the battery might be overcharged.
2. Voltage Sensitive Relay: This is a better version of the ignition-triggered relay since it provides the option for auto cut-off when the voltage of the battery reaches 13.7V DC.

Battery to Battery Smart Relay

Battery-to-battery chargers are also called B2b chargers and DC-to-DC chargers. Newer emission norms impose more restrictions on the vehicle’s alternator. These vehicles use smart alternators, which reduce the charging voltage once they sense that the starter battery is fully recharged.

To eliminate the problem of the reduced charging voltage, the charging connection of the leisure battery is tapped from the starter battery itself, instead of using a split charge relay. Therefore, the smart alternator keeps on providing the full charge voltage until both batteries are completely charged.

Solar Panel Charging

Solar panels can also be used to generate electricity for charging batteries on caravans and motorhomes. However, since solar power isn’t guaranteed in all times of day and in all weather, it should not be used as the primary source of electric power.

Additionally, solar panels are not connected to the battery directly for charging. They go through equipment known as solar controller, which ensures that the charging current has a safe value that meets the battery requirements. However, charging through solar panels can be slow, and it can take about two whole days for the leisure battery to charge completely.

Hook Up Battery Charging

Hook up battery charging involves connecting the battery charger to an AC hook-up of a facility. This method can generally recharge leisure batteries in camping sites or at homes. Motorhomes usually have a hookup inlet on the side, which is connected to the hook-up outlet of the campsite.

When the campervan is connected to the hook-up, the leisure battery charging will begin. Additionally, all the electric equipment inside the campervans can be run directly through the electrical hook-up without consuming battery charge.

However, this method only works for campervans that have access to electrical hook-ups on the campsite or any other similar location. For people who frequently engage in off-grid camping, this method is not very suitable.

Generator

Camping generators are another good solution to charge the battery. The charging characteristics of a generator is very similar to the AC mains line. However, using them directly is not a good idea since their voltage is not regulated and it keeps on varying with the generator RPM.

The recommended method is to connect the original battery charger to the generator’s AC output. This can provide a regulated power supply to the battery. One thing to note is that camping generators usually provide a low current output, so it will take a long time for the leisure battery to fully charge.

Wind Power

Wind power works similarly to solar power when charging a leisure battery. It utilises a Vertical Axis Wind Turbine (VAWT) system mounted on top of the motorhome. The VAWT rotates and generates electricity with strong gusts of winds. The electricity goes through a controller that regulates its voltage, and then to the battery charger.

Since wind is quite unpredictable, this method can only be used as a secondary charging option for saving time in leisure battery charging through primary means (such as AC mains or generator).

Which Charging Method to Use?

The right charging methods for a leisure battery are highly variable based on the situation. For instance, if you intend to spend a lot of time off-grid camping, you will need to have a camping generator to charge the leisure battery. Along with that, a secondary charging method like solar panels or wind turbines is always a good idea to have.

However, if your motorhome will spend a lot of time on a campsite, an electrical hookup is a good way to charge the leisure battery. Secondary charging methods like solar or wind power are also useful in this case as they can reduce charging time and costs.

For motorhomes in motion, the split charge relay or battery-to-battery charger is a good way to charge the battery. Regardless of which method you follow, remember to take proper charging steps to ensure a safe battery voltage.

Can You Charge Your Leisure Battery While Driving?

Yes, all leisure batteries can be charged while driving. This is done through the engine-driven alternator, which is present in every type of vehicle. The vehicle’s alternator starts to output a DC current once it reaches a certain rpm. This current then charges the starter battery of the vehicle. The leisure battery can be charged through this setup by using a split charge relay or by using a battery to a battery charger.

What are the Different Types of Leisure Battery Chargers?

There are many different types of charger options available for leisure batteries. Some of the common types are:

Basic chargers

Basic chargers, also known as manual chargers, do the job of providing the charging current to the battery. However, these cannot sense the charge level of the battery. Even when the battery is fully charged, these chargers keep providing the current supply. This can result in overcharging, eventually causing damage to the battery. Therefore, if using these types of chargers, you need to constantly monitor the battery while it is being charged.

Semi-automatic chargers

Semi-automatic chargers are a step up from the basic chargers. In semi-automatic chargers, the charger can sense the current voltage of the battery. When this charger senses that the battery is fully charged, it can turn off the supply of current.

Certain models of these chargers provide the option to manually set the cut-off voltage. This voltage can vary from battery to battery, so it is a good idea to refer to the manufacturer’s instructions to find out the fully charged battery voltage.

Fully automatic chargers

Besides providing a supply cut-off feature when the battery is completely charged, fully automatic chargers come with several other benefits. For instance, these chargers support a multi-stage charging process.

In the first stage, called the bulk stage, the charger replenishes the majority of the battery charge with maximum voltage and current. After this stage, the charger enters an absorption stage where it keeps a constant voltage supply and drops the current. Lastly, the charger goes into a float stage where the current is constant but the voltage drops slightly. The benefit of the multi-stage process is that the battery is charged in an efficient manner, leading to longer battery life.

Modern fully automatic chargers also come with a battery temperature sensor. These chargers adjust the charging voltage and current based on the battery temperature to avoid battery damage in extreme temperature conditions.

Pulse Charging

Pulse charging is a beneficial feature of modern chargers. In pulse charging, the charger provides short pulses of high voltage and high current followed by short pulses of low voltage and current. Pulse charges eliminate the phenomenon of stratification in the battery. Stratification causes the concentration of sulphuric acid at the bottom areas, which often causes internal corrosion of the battery.

Portable Generators

Portable generators can be directly used as chargers, provided there is a controller for maintaining the appropriate voltage. However, charging using this method is going to be extremely slow.

Using Your Car’s Alternator

Using the car’s alternator as a leisure battery charging device works well when the vehicle is on the move. This method is not recommended to charge the leisure battery frequently, as it does not replenish the battery’s capacity to full extent. Using basic, semi, or fully automatic chargers is important from time to time to ensure that the battery gets fully charged.

Solar Powered Chargers

Solar-powered chargers are best to top up the battery charge regularly. However, these chargers are not recommended if you are looking to charge your leisure battery from zero to full capacity. These chargers are also a great option to charge a leisure battery in storage, which maintains its optimal health.

Wind-Powered Chargers

Wind-powered chargers work similarly to solar chargers, replacing solar panels with wind turbines.

However, since wind gusts are highly unpredictable, wind-powered chargers are the least common leisure battery charging method in practice.

How Do You Know If Your Leisure Battery is Fully Charged?

It is easy to tell if a leisure battery is fully charged. There are two methods to determine the same. Here are these methods:

Using Voltage Readings

Using voltage reading is the best and the easiest way to differentiate between a charged and a discharged battery. The voltage of a battery always varies with its state of charge.

Generally, if the battery voltage is between 12.7 to 12.9 V, it is considered fully charged. Anything less than 12.7 V will require charging.

In case the battery voltage is below 12.4 V, the battery is deeply discharged. It is recommended to use a smart charger for charging a deeply discharged battery.

The battery voltage can be measured by using a voltmeter between the open battery terminals. Eco Tree Lithium’s batteries come with a Battery Management System (BMS) that provides real-time voltage reading of the battery on display.

Specific Gravity Method:

The charge level of a battery can also be determined by the specific gravity of the electrolyte.

While this is not a very popular method, it is a possible way to determine the charge if the voltage readings aren’t available.

However, this method does not work for sealed batteries or any lithium batteries. It is only limited to the flooded and unsealed lead acid battery.

The specific gravity of the battery electrolyte decreases as the battery is discharged, due to the chemical reactions taking place inside the battery. The decrease in specific gravity is linear to the discharged amp hours.

Similarly, as the battery is charged, the specific gravity of the electrolyte will increase.

It is possible to measure the specific gravity of the electrolyte in each cell using a device called a hydrometer.

When fully charged, the lead acid batteries will have a specific gravity of 1.265 at 80° F.

Temperature is an important factor to consider because the specific gravity varies significantly with temperature.

To adjust for temperature differences, add 0.004 to the specific gravity reading for every 10° F increase over 80° F, and subtract 0.004 for every 10° F decrease below 80° F.

Useful Tips for Leisure Battery Charging

Here are some useful tips concerning leisure battery charging that can help to prolong its lifespan:

• Check the state of charge of your leisure battery at least once a month.
• Once you have used the leisure battery, recharge it as soon as possible. This not only maintains good battery health, it also means that the battery will be in a ready state when you need to use it the next time.
• Once in every six weeks or so, remove the battery and charge it with the manufacturer-provided (or recommended) leisure battery charger.
• If using a non-sealed battery which requires electrolyte top-up, use de-ionised water or distilled water for the top-ups. Using tap water or even plain filtered water is a wrong practice as it often contains minerals that can damage the battery due to electrolyte contamination.
• If a battery is deeply discharged, it can freeze completely. Therefore, prefer to retain some charge in the battery before the next charging cycle.
• Only use the appropriate charger with the leisure battery. Leisure battery chargers don’t have a cross-functionality, an AGM charger will not work with an LFP battery and vice versa.

Where to Buy a New Leisure Battery?

Eco Tree Lithium is the one-stop for high-quality leisure batteries for sale. We manufacture a wide range of Lithium Iron Phosphate (LFP or LiFePO4) batteries that are considered the best compared to any other type of leisure battery.

These batteries have the longest lifespan along with a very rugged build quality.

There is a Battery Management System that optimises the battery condition during charging and discharging. Additionally, all batteries come with a 6-year warranty which very well demonstrates the superior quality of these batteries.

Conclusion

Charging a leisure battery is not a complex science. Every leisure battery comes with a manufacturer-provided user manual that mentions the best charging methods for the battery. When using any charger with the battery, it is important to keep in mind the recommendations of the manufacturer since every type of battery is designed differently.

Rest assured, if you follow healthy battery charging habits and use the tips we mentioned above, your battery will last for its entire intended lifespan and more.

Frequently Asked Questions (FAQs)

Here are the answers to some common questions regarding lithium battery charging:

1. Can I charge a leisure battery with a normal charger?

The leisure battery should be charged with the charger provided with the battery. You should never use a lead acid battery charger with a lithium battery and vice versa. Additionally, leisure batteries are deep cycle batteries and cannot be charged with a normal car batteries charger.

2. What is the best way to charge a leisure battery?

The best way to charge a leisure battery is by using the manufacturer-recommended charger ( a (fully automatic charger if possible), and charging the battery through an electrical hook-up.

3. Can you charge a leisure battery from the mains?

Yes, you can easily charge a leisure battery from AC mains. For this purpose, it is recommended to use the manufacturer’s battery charger instead of the caravan or motorhome’s onboard charger.

4. Will a 10W solar panel charge a leisure battery?

Yes, a 10W solar panel can charge a leisure battery. However, the charging occurs at a very slow rate and it can take many weeks for the battery fully charge level. Using a 10W solar panel is a good way to trickle charge the battery, for top-ups, and for maintaining the battery’s charge level.

5. Will a 100W solar panel charge a leisure battery?

Yes, a 100W solar panel is a great way to fully charge a leisure battery. A 100 W solar panel can charge a 100 Ah battery in 12 hours, so it can take two to three days to fully charge the battery depending on the amount of sunlight available in the location.

6. Why is my alternator not charging fully?

Modern alternators are smart alternators, designed to stop providing the charging current once the vehicle battery fully charges. This can stop power to the leisure battery as well, meaning that it will not be fully charged. Use a battery to battery charger to avoid this issue.

7. Will my leisure battery be affected if I don’t charge it fully?

Yes, if the battery is left in a discharged state for too long, its health will be affected. Therefore, it is important that the batteries are charged fully from time to time.