How to Tell If RV Battery is Bad?

Updated on

Your battery recharges slowly: If the battery isn’t being completely charged or is charging at a slower pace, there may be a problem and the battery has to be changed. A decent guideline is to change your RV batteries every five years or so.

Batteries for RVs often have a long lifespan.

The several kinds of RV batteries that are available and their locations are briefly discussed in this article.

The rest of it then goes into great detail on the testing processes.

Various RV Battery Types

RV batteries come in two varieties:

  • Battery starters
  • Long-lasting batteries

#1. Battery Starters

Starter batteries are designed to provide a strong burst of electricity to turn on the engine.

They are often seen in boats, RVs, and cars as well.

The hybrid battery type, which is far more popular in boating than in RVing, has both starter and deep-cycle functions.

Before the starting battery runs out of power and has to be recharged, the engine can normally start a specific number of times.

#2. Deep Cycle Battery

Starter batteries and deep cycle batteries are two separate things.

This is so because they serve various purposes.

12-volt deep cycle batteries are designed to consistently provide a constant flow of energy, rather than a powerful burst of cold cranking amps to start an engine.

It is specifically what an RV needs to run its heating, refrigeration, and lighting without experiencing frequent power outages.

Deep cycle batteries come in a variety of forms, including AGM, lead-acid, gel, lithium, and others.

A thorough discussion of each category, however, is beyond the purview of this article.

These kinds are discussed in this text, however, as they become pertinent.

Below is an illustration of a typical lead-acid deep-cycle RV battery:

Except for the lithium variety, all batteries should only be discharged to between 40 and 60% in order to protect the battery’s cell structure.

The minimum safe charge level varies depending on the manufacturer and the product information, so check the handbook or specs for your battery to be sure.

So even if a battery has a 110Ah capacity, it’s probably only safe to utilize around 50–55Ah of that capacity while the battery is completely charged.

The lithium battery type can withstand being discharged to 20% or less.

It’s one of the benefits of lithium, although they are much more costly and need pack replacement.

Most RV owners won’t have lithium house batteries installed unless they were upgraded by a previous owner or installed at the manufacturer when the RV was built.

That’s unusual in both situations.

The Renovy LiFoPO4 Deep Cycle 12V 100Ah battery is the ideal lithium battery for an RV.

RVers may benefit from the optional monitoring screen as well:

Suggestion reading: Why Is My RV Battery Draining While Plugged In?

Locations for RV Batteries

As you may anticipate, the starting battery will be positioned up front.

The 12-volt house batteries, also known as coach batteries, are normally located someplace in the main coach area.

Seating underneath the dinette is typical.

However, if you’re uncertain, you may need to consult the RV’s handbook or look about to find them.

How to Recognize a Malfunctioning Deep Cycle Battery?

It is possible to test a deep cycle battery using a specific approach.

Even though deep cycle batteries are typically 12-volt devices, the voltage isn’t constant, hence the value is rounded down.

A little higher voltage (12.7 V) will appear at the start, indicating a full charge.

The voltage will then start to dramatically drop as the battery loses all of its reserve energy.

The voltage measurement should be about 12.2 volts at 50% capacity, and it will be around 11.98 volts at 20% capacity.

Two or three of the following instruments are need to complete the operation.

  • Tester for battery load
  • OR Hydrometer
  • DC Voltage Gauge

Through our discussion of how to test your batteries, we will go through each of them.

There’s no need to question whether the battery in your RV is bad or not.

That at least provides comfort.

When Working With Batteries, Use Caution

When handling batteries, protect yourself by using heavy-duty gloves and safety glasses.

They may contain acid or other things that may leak out, depending on the kind of battery.

Wearing safety gear is crucial as a result.

Additionally, for their own safety, if you have children, take them somewhere else to play.

Performing a Deep Cycle Battery Pre-Check

A full charge is ideal for test results that are more accurate.

When the battery can’t be charged, give it a break for a half-hour to an hour before going back to it.

Given that deep cycle batteries need time to settle, the rest period will aid in obtaining more accurate battery readings when utilizing the aforementioned equipment.

With batteries, a visual pre-check is helpful to search for anomalies that could point to a problem.

The following are some of the main visual indicators to look for during a pre-check:

Battery casing with a bulge or that is otherwise not in the same shape as it typically would be indicates that the battery is damaged.

If it stopped charging, it would need replacement.

The battery now poses a danger to safety.

It has to be taken out and replaced.

Leaking – Even a little amount of battery leaking is concerning.

The battery should be fully written off if there is major leakage.

Even though batteries sometimes leak, this is a dangerous indicator, and we would want to replace the battery if we saw it during a check.

Broken or damaged terminals must be replaced immediately since they serve as the link for hooking into objects.

That battery is dead when one or more of them have visible damage or have been severed.

Never use it again and replace it right away.

Damaged plastic on the battery’s case might indicate a fracture or other kind of break.

This suggests that the battery was either damaged during shipment or that it was previously bulging out and pushed it to break.

In either case, the battery has to be changed since there is no guarantee that it is safe to use.

Use of a damaged battery is not recommended at all.

Changing color – It’s not acceptable for the battery or the case’s color to change.

It implies that there may be an interior leak or worse internal problems.

Once again, the battery must be discarded and not utilized.

Replace the damaged battery and delete any observables you see from the list above.

It’s preferable to swap it out with a compatible battery of the same brand and model while doing so.

A serious safety concern arises from damaged batteries.

Don’t take a chance by using them indefinitely.

Related Also: How to Troubleshooting RV Battery Disconnect Switch?

How a Deep Cycle Battery Is Tested

Voltage Checking the Battery:

Check the voltage reading for each coach battery after carefully inspecting your battery bank and being certain that everything seems to be in order.

The greatest place to start when learning how to test an RV battery is with this.

Later in this essay, further stages are covered.

As an aside, boat owners may use the same method to test a deep cycle marine battery that isn’t holding a charge.

If there is an issue with one or more battery cells, it will be evident from the DC voltage measurements obtained during a deep cycle battery voltage test.

After the RV batteries are completely charged, it is wise to wait a few hours before checking the voltage.

The batteries may settle for more precise measurements as a result.

Test each deep cycle battery with a multimeter or, maybe, a voltmeter.

Check the voltage readout to make sure the battery is charged.

For approximations of voltage readings and charge percentages, please see the table below:

11.98 V20
12.04 V30
12.12 V40
12.20 V50
12.28 V60
12.36 V70
12.46 V80
12.64 V90
12.70 V100

The voltage readings will typically range from 12.2 volts, or about a 50% charge level, to 12.7 volts, or about a 100% charge level.

What Value Should a Fully Charged 12 Volt Battery Show?

A voltage of around 12.7 volts will indicate a 100% charge level.

It’s helpful to test the deep cycle battery if it won’t charge completely.

Examine the connection to the deep cycle marine battery if charging is the issue.

Otherwise, load testing is required.

Due to a disproportionately high charge loss, the deep cycle battery may have suffered damage.

You may use a voltmeter or a multimeter.

They could validate a measurement of 11 volts or less.

When the battery’s valid volt measurement falls below 11 volts, it is likely no longer functional and has to be replaced.

A measurement of 0 volts would indicate a short-circuit.

To determine why, a more thorough examination is necessary.

Can You Load Test A Deep Cycle Battery?

It can, really.

The purpose of load testing is to verify how effectively a deep cycle battery maintains its charge.

When it has difficulty doing so or drains rapidly, it is most likely that the battery is malfunctioning, it is sulfated (more on this in the next section), or the interior cells have been harmed as a result of improper charging techniques.

How to Test a Deep Cycle Battery Under Load?

Battery load testing equipment is needed to properly load test a battery if you’re going to do it yourself.

How to do a deep cycle load test is as follows:

Remove any cords that are connected to the battery connections.

Connect the battery connections to the battery load tester.

You may tell it to provide a small load that is rated at half the battery’s Cold Cranking Amps (CCA) capacity.

The load tester will validate the readings when it is done.

For 30 seconds, a battery should maintain above 9 volts and potentially below 11 volts.

This must stay till it is finished.

The RV battery has to be changed, however, if the charge is applied to the battery during the test and then quickly dissipates thereafter.

Recommended reading: How to Store an RV Battery for Winter?

Symptoms of Sulfated Batteries

Instead of constantly undergoing a full charging cycle, batteries suffer when they are only half charged.

Sulfation may develop when a deep cycle battery is partially recharged.

Sulfate crystals form and persist in the battery at this location.

The negative battery plates accumulate sulfate when the battery is regularly discharged over extended periods of time.

Later on, you’ll see decreased performance when the charging capacity falls as a result.

Sulfated batteries may be partly recovered in a few different methods.

But generally speaking, it’s preferable to simply replace them.

What Is the Deep Cycle Battery Replacement Cycle?

It’s not unusual for RV owners who acquired their motorhome or towable from a previous owner to have charged the batteries improperly or frequently just partially.

As a result, they may not realize the coach’s battery pack is damaged until it is too late.

For most buyers of used RVs, it is sense to include in the expense of replacing the complete battery pack with a new set of batteries since it is such a common problem.

The projected lifetime of new batteries, or the number of recharge cycles (whichever comes first), varies depending on the brand, model, and type.

New batteries should, therefore, endure for at least a few years.

To get the most out of your batteries, we advise that you strictly adhere to the manufacturer’s instructions.

Deep cycle batteries often have a few hundred recharge cycles.

The exception is lithium, which can often withstand tens of thousands of recharge cycles.

Despite the possibility of a higher number of cycles, batteries that are mistreated in terms of recharging and discharging are more likely to fail.

As a result, how a battery is cared for might affect how long it lasts.

Lithium is the ideal RV battery for dry camping.

This is so that when there isn’t enough solar energy to raise its charge level, it may be severely drained.

Lithium is quite useful when boondocking on a cloudy day and not wanting to waste petrol by driving around to use the alternator to recharge the batteries.

Final Thoughts

It is possible to determine if the RV battery is defective using the appropriate tools.

Lithium batteries aren’t an exception, however deep cycle RV batteries do degrade more often.

They can withstand greater abuse during charging and discharging cycles, but they are still susceptible to being mismanaged by the RV owner and suffering damage as a consequence.

Suggestion Videos from Youtube about How to Tell If RV Battery is Bad

RV Battery Testing Quick Tips, presented by KOA – RV Education 101
Testing RV Battery For Charge & Condition – RV Lifestyle and Repair
RV Tips – How to check your battery and charging system – ShawTVSSM
Photo of author
Ryan is a RV product expert with nearly a decade of experience researching, developing, and testing RV products.

Leave a Comment