Deep cycle batteries are undoubtedly one of the best power pack choices. However, as excellent as they are, they can encounter issues as well due to handling, storing, outdoor conditions, or age. Knowing how to tell if a deep cycle battery is bad can help you save yours in time or prevent early signs of decline from progressing.
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Knowing your deep cycle battery's condition is crucial to avoid hassle. Imagine being a camper and getting stuck outdoors with no source of power! Make it a habit to check your Outbax battery for any issues and save yourself the trouble. Read on and refer to this little guide to help you determine the telltale signs of a deep-cycle battery that has gone bad.
How to Tell If A Deep Cycle Battery Is Bad?
Not Charging At All
Obviously, a battery that doesn't charge in the first place either needs a repair or a replacement. If your deep cycle battery is like this, the best move would be to do a test and ensure the problem is within the power pack and not on external factors like your battery charger. A battery's charging voltage is a good indicator of its overall condition, and you can easily do this with the help of a voltmeter or multimeter.
Inability To Hold Charge
Is your battery draining faster than usual? This could be a warning sign of underlying issues, especially if accompanied by heating. Make sure to have it checked right away, as this could lead to safety risks such as a fire. It's normal for a battery to be warm, but anything hotter than this is likely dangerous.
Remember, a fully charged 12V battery should have a 12.7V to 13.2V voltage reading. If you have it completely topped up but the voltage is showing a 12.4V rate or less, this means that your battery is sulfated, which commonly occurs when you leave your battery unused and drained for an extended period.
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Meanwhile, a reading of 0 volts could indicate a short circuit, while not reaching higher than 10.5V while charging is a sign that your battery is dead. This is why knowing how to test deep cycle battery is important as it helps you determine whether something is wrong with the power pack early on.
Slow Down In Performance
Deep cycle batteries are known for their excellent quality, particularly lithium deep cycle batteries like a LiFePO4 battery. If you notice your battery declining in performance, i.e., taking too long to charge or being unable to accommodate its usual load, this could be another sign of decline.
Physical Degradation
Your deep cycle battery's physical appearance alone will tell you immediately if it's damaged. Inspect it occasionally to see broken terminals, bloating, cracks, leaks, and discolouration. Damaged terminals can cause short circuits, which may lead to an explosion. This is crucial especially for camping batteries and caravan batteries as they’re mostly used outdoors and are more vulnerable to the elements.
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On the other hand, overcharging is the usual culprit behind bulges or bumps in your battery case. Other signs of improper handling would be ruptures or splits. While these don't affect the battery's performance much, they still pose risks to the user and should be labelled as unsafe to use.
If you're using wet-cell batteries, keep in mind that their water levels should always be maintained. Constant exposure to air may dry out the paste surrounding the lead plates and cause sulfation. Sulfation is one of the most common battery issues. It is called the build-up of lead sulfate crystals in the pores of active material in the battery plates. This is also caused by depriving your battery of a full charge. Lastly, any discolouration, even in one battery cell, makes the entire pack unsuitable for use, indicating that you should replace your battery already.
What Causes Decline in Deep Cycle Batteries?
The most common causes of deep cycle battery issues spring from mishandling. This is why it's crucial to follow the manufacturer's instructions on charging, discharging, and keeping your battery in optimal condition during and after use. Below are some of the top culprits behind a bad deep-cycle battery:
Overcharging
Leaving your battery plugged in beyond its required charging time or charging at excessively high voltage can lead to permanent damage. It's always best to watch your charging time and use the appropriate charger for your battery chemistry.
Frequent Discharging
Perhaps one of the best things about deep cycle power packs is their ability to be safely discharged by up to 80%. Conventional batteries can typically be charged down to half of their capacity only, so going for a deep cycle battery means you get a longer runtime too.
However, if drained too quickly and put to use without a proper recharge, this could affect your battery's lifespan and performance. It's still best to discharge within a considerable level, preferably not any deeper than 50%.
Sulfation
As mentioned, sulfation occurs when crystals form on the plates inside the battery from idle or drained for an extended period. This is one of the top causes of issues among batteries of all types. To prevent sulfation, it's recommended to recharge your power pack every few months, even if you're not using it regularly.
How to Test Deep Cycle Battery?
Aside from voltage testing, a load test is another effective way to test your deep-cycle battery's condition. This method can also be done via a digital voltmeter. Simply hold the prongs of your voltmeter to the right battery terminals, press the start button, and see where your voltage drops, too.
However, remember that before load testing it, the battery should be fully charged and left to sit 12 hours before the procedure. This way, the residual charge is already released, and you'll likely get a more accurate result of your battery's performance.
Note that a healthy battery should be able to hold 9.6V to 10.5V under the load for 30 seconds. If your deep cycle battery maintains this for only a few seconds and starts to drop gradually or immediately falls to zero, this is a clear sign of a battery problem often referred to as "open-cell." It can be the result of a manufacturing error, sulfation, or overheating and once your battery reaches this level, there's no way to fix it anymore.
Deep cycle batteries are considered one of the best investments for avid outdoor adventurers and homeowners for power backup purposes. It’s no surprise that these are often picked as the best camping batteries, caravan batteries, or even house batteries.
If you're also looking for high-quality yet affordable lithium deep cycle batteries for caravans or homes, check out our collection at Outbax. We have a wide range of LiFePO4 batteries available in different sizes to accommodate varying power requirements, perfect for your next trip exploring the great Aussie outdoors. Shop now!
Last Updated on April 5, 2024
Frequently Asked Questions
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What are the most common signs that a deep cycle battery is going bad?
The most common signs of a failing deep cycle battery include a noticeable drop in performance, such as not holding a charge for as long as it used to, and taking much longer to fully charge. Physical signs are also a key indicator, such as swelling or bulging of the battery case, cracks, or leaking acid. A battery that gets excessively hot during charging or use is another major red flag.
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How do I physically inspect a deep cycle battery for damage?
To physically inspect a deep cycle battery, first ensure it is disconnected from any load or charger. Look closely at the battery case for any signs of swelling, bulges, or cracks, which can be caused by overcharging or internal cell failure. Check the terminals for corrosion, which can impede electrical flow, and inspect the casing for any signs of leaking electrolyte, which is a definitive sign the battery is damaged and needs to be replaced safely.
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What does a low voltage reading tell me about my battery's health?
A low voltage reading after a full charge is a strong indicator that the battery is failing. A healthy, fully charged 12V deep cycle battery should read between 12.8V and 13V. If your battery consistently shows a voltage of 12.4V or less after charging, it means it can no longer store sufficient energy and has likely lost a significant portion of its capacity.
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Why won't my deep cycle battery hold a charge anymore?
A deep cycle battery that won't hold a charge is a classic symptom of old age or internal degradation. Over time and with many charge/discharge cycles, sulfation can occur on the lead plates in lead-acid batteries, or the active materials in the cells can break down. This reduces the battery's ability to store energy effectively, causing it to lose its charge quickly even when not in use.
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What is a load test and how does it determine if a battery is bad?
A load test is the most definitive way to determine a battery's health. It involves applying a specific electrical load (current draw) to a fully charged battery while monitoring its voltage. A healthy battery will maintain a stable voltage under the load, while a bad battery's voltage will drop rapidly. This test simulates real-world usage and reveals if the battery can still deliver adequate power when needed, which a simple voltage test cannot.
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Can a deep cycle battery be bad even if it shows a full voltage?
Yes, a battery can show a full "surface charge" voltage (e.g., 12.8V) when tested with a multimeter but still be bad. This resting voltage doesn't indicate the battery's ability to provide power under load. As soon as you connect an appliance, the voltage on a bad battery will plummet. This is why a load test is crucial for an accurate diagnosis.
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What causes a deep cycle battery to swell or bulge?
A deep cycle battery case swells or bulges due to overcharging, excessive heat, or internal short-circuiting. These conditions cause a buildup of gas inside the sealed battery at a rate faster than it can be safely vented. This pressure forces the battery case to expand. A swollen battery is dangerous and should be decommissioned and replaced immediately.
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How does the age and cycle life of a battery indicate it might be failing?
Every deep cycle battery has a finite "cycle life," which is the number of charge and discharge cycles it can endure before its capacity drops significantly. A typical lead-acid battery might last 300-500 cycles. If your battery is several years old and has been used regularly, its poor performance is likely because it is simply reaching the end of its natural service life.
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Why does my battery get excessively hot when charging?
A battery getting very hot during the charging process is a serious warning sign of an internal problem. It often indicates an internal short between the cells. This causes the charging energy to be converted into heat instead of being stored chemically. This condition is inefficient, dangerous, and can lead to battery failure or swelling.
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What tools do I need to test a deep cycle battery?
For basic testing, you will need a digital multimeter to check the battery's voltage. For a more conclusive assessment of its health, a dedicated battery load tester is required. Safety gear, including safety glasses and gloves, is also essential when handling batteries, especially lead-acid types.
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How is testing a deep cycle battery different from testing a car battery?
While both can be tested with a multimeter for voltage, the most meaningful test—the load test—is different. A car battery is tested with a high, short burst of current to simulate starting an engine. A deep cycle battery should be tested with a smaller, sustained load over a period of time to check its capacity to provide continuous power, which reflects its intended use.
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Does a battery that discharges very quickly mean it's bad?
Yes, a battery that discharges much faster than it used to under the same load is a clear sign that it is failing. This indicates a significant loss of capacity, meaning the battery can no longer store the amount of energy it was designed to hold. As the internal components degrade with age and use, its ability to retain and deliver power diminishes.
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If my battery is bad, why is a LiFePO4 battery a better replacement?
A LiFePO4 (Lithium Iron Phosphate) battery is often a better replacement because it offers a much longer lifespan, typically providing thousands of charge cycles compared to just a few hundred for a lead-acid battery. LiFePO4 batteries are also more efficient, lighter, can be discharged more deeply without damage, and feature an integrated Battery Management System (BMS) for enhanced safety and longevity.
