Alternative power sources

How to Charge RV Batteries

Everything in an RV depends on the battery to function. Without a properly functioning source of power, an RV loses its status as a hotel on wheels.

However, just like any other battery, an RV battery can lose power or need to be recharged. Knowing how to charge it will allow you to enjoy all the benefits that come with RVing.

There are 4 ways that you’re able to charge your RV’s deep cycle battery:

  1. While driving, your alternator will charge your RV battery
  2. When you’re connected to shore power, your converter will trickle charge your RV battery
  3. When you run your generator, you’re also charging your RV’s deep cycle battery
  4. And finally, you can opt to go green and use solar power

Your RV’s stock converter — which converts 110 volt AC power (aka shore power or generator power) to 12 volt DC power — is generally a weak charger and is only able to trickle charge your battery.

Be advised that if your battery is below 50% capacity, 8 hours or more could be needed using your stock RV converter. You could upgrade to a 4-stage smart charger to charge at a quicker rate — usually around 2 hours for a full recharge. External smart chargers go for around 50 dollars whereas a complete internal converter overhaul could cost you upwards of 500 dollars.

What Is an RV Battery?

How to charge RV batteries

Basic batteries are simply devices to store electrical power. They cannot generate their own power but can hold it for later use by storing it in chemical form. Because they only store power, they will need to be recharged once they are depleted.

Why Do You Need an RV Battery?

In your RV, the battery runs all systems and powers appliances in the coach. Most kitchen appliances such as a microwave, coffee maker, and toaster use the majority of electricity in an RV.

Air conditioning can also take a lot of energy as well as powering a slide-out. Bathroom devices like hairdryers are also high on the list of items that will use up power quickly.

The house or coach battery is different from the battery used to start the engine of your RV. It is designed to run for a longer period, so you can use the amenities while dry camping or boondocking, e.g., camping without hookups.

Battery Ratings and Sizes

Most manufacturers will indicate the amount of power that a battery can store. This is a measurement in amps of current, providing a value for what should be used before the battery will be drained to 80% discharge.

Most RV batteries are deep cycle batteries with a time measurement of 20 hours for battery drain. So you will often see RV batteries with a 20-hour amp-hour rating.

Batteries are also sized and usually have standard sizes.

You may have heard common terms like a “group 24 battery” or “type 27 marine battery.” These numbers are referring to the Battery Council International, or BCI, Group Number of the battery. These numbers define the physical dimensions of the battery case. This is important as some applications call for specific case sizes.

While the BCI does not determine the Amp Hours (AH) rating for the batteries, there is a correlation between case size and AH rating. For deep cycle batteries, the larger the case size the more capacity the battery will usually have.

BatteryStuff.com, See URL – https://www.batterystuff.com/kb/tools/bci-battery-group-sizes.html

# 1 – Example Sizes for Batteries:

  • Group 24
  • Group 27
  • Group 31
  • Group 4D
  • Group 8D

Look on the side of the battery for a sticker that will tell you the specifications for that particular battery.

When you purchase a new RV, it will usually come with a Group 24 or Group 27 size battery. It could have a single battery or two batteries.

#2 – Understand Voltage

RV batteries can store 12 volts of direct current (DC) and are usually called deep-cycle batteries. These batteries are designed to be used and charged multiple times without harming the battery.

Each battery is measured in amp hours which indicates how many amps are drawn per hour. For most batteries, this will be over a period of 20 hours.

The battery is then used to charge the systems within the RV, including appliances which are designed to run on 12 volts of power.

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#3 – What Is a Battery Bank in an RV?

Battery bank in an RV

You get a battery bank by joining two or more batteries together. By connecting several batteries, you will get access to greater amounts of voltage or amps (depending on the connection) for times when you need more power than a single battery can provide.

The minimum for an RV is usually a single Group 24 battery that can have about 50 amp hours while some higher-end or luxury RVs can have a group four Group 8D batteries to provide more than 1,000 amp hours.

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#4 – How to Join RV Batteries

To connect RV batteries in a series, use a jumper wire to connect the batteries. Connect the negative terminal of the first battery with the positive terminal of the second one. Then use another set of jumper cables to connect the other positive and negative terminals.

Each battery used should have the same voltage and amp rating so they are compatible. Two 6 volt RV batteries will provide 12 volts without changing the amps when they are connected in series.

A parallel connection battery bank will provide a greater current while keeping the voltage the same. So joining two 6 volt batteries in parallel will remain at 6 volts but will increase the number of amps.

Create a parallel connection by connecting the two positive terminals with the two negative ones. A series-parallel bank can also be done but will require four batteries at a minimum.

If you need to increase your RV’s battery bank, one of the easiest ways to upgrade is to get rid of one 12-volt battery and replace it with two 6-volt golf cart batteries. Wire the two batteries in series to increase the capacity of amp-hours from approximately 70 to 220.

Don’t mix and match batteries when creating a battery bank. Instead, use the same brand and type to avoid any problems.

#5 – Charger Sizes and RV Banks

Before purchasing new batteries, make sure the charging system that came with the RV is big enough to charge the new batteries. This will prevent you from purchasing batteries that can’t be charged or require an upgrade to a larger charging system.

#6 – Stand Alone Chargers: Single Stage and Multi-Stage RV Battery Chargers

When charging a battery, a lot of amps will flow in the beginning but, as the amp-hours, the battery is storing increases, the rate will gradually decrease. This method of charging with a fixed voltage that tapers the amperage is called single-stage charging.

A single stage can be inefficient and runs the risk of either overcharging or undercharging the batteries. They also don’t push the battery up to a high voltage which is often recommended to extend the life of the battery.

A multi-stage charging system, on the other hand, is more efficient. It gives the battery current depending on the state of its charge. When the battery is more depleted, a lot of current will come initially, but then decrease once it is more charged.

#7 – Stages of a Multi-Stage Charger

Multi-stage chargers usually have three states: bulk, absorb, and float

The bulk stage is used when you want to quickly charge a battery from a very low state to about 60-80% charge. The charger does this by giving the battery as much current as it possibly can.

Depending on the battery, the bulk voltage stage may be reached at around 14.3 to 14.8 volts. Then the charger switches and only gives as much voltage as necessary to keep the amps constant or at a particular voltage.

The battery now needs less current to maintain its voltage level as it continues to charge and absorb as much current as it can.

In the final stage, the float stage, the battery is almost fully charged so the charger changes and maintains a lower voltage. This is usually around 13.3 to 13.6 volts.

Because the battery is already quite charged, it doesn’t need a lot of current to maintain a lower voltage, so the charger compensates accordingly. Over time, the current needed to maintain the float stage will also decrease until the battery is fully charged.

#8 – Turning off a Multi-Stage Charger Early

A multi-stage charger can be turned off at any time while the battery is being charged. Although the battery will be more charged than before, it still won’t be fully charged.

At this time, the battery will settle to is internal voltage and that level can change. Ideally, it will be a higher voltage than before the battery was charged. However, if the battery does not get charged enough, it could be lower than you expect.

If you plug the multi-stage charger back in to finish charging the battery, it will usually start the entire charging process from the first stage, bulk, and move through the rest of the cycles.

#9 – Equalizing Using a Multi-Stage Charger

Some multi-stage chargers also have an additional stage for equalizing wet cell batteries. More on this in a later section.

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#10 – Long-Term Charging with a Multi-Stage Charger

Instead of plugging into an outlet to maintain a charge, a multi-stage charger can also be used as an alternative. Many multi-stage chargers vary in the way they manage this kind of charge though.

Some will maintain the voltage at the float stage indefinitely. Others may start over and cycle through the bulk and absorb stages several times.

To extend the life of the battery though, it’s a good idea to move the charger out of the float stage from time to time and use bulk and absorb as well.

What Is Battery Sulfation?

RV batteries need to be constantly monitored to check how much power is available. If the battery falls too far below the necessary voltage, sulfation can result.

This is when lead sulfate crystals build up and cause problems in the battery. Sulfation can result in longer charging times or battery failure.

Reversible sulfation can be remedied by having someone do a controlled overcharge to dissolve the crystals. However, its best to consult a professional to make sure it is done properly and will effectively return the battery full functionality.

Prevent sulfation by never letting your batteries drop below 20 percent (12.4 volts) charge.

#1 – Maintenance of RV Batteries

To prolong the life of your battery, it will need to be regularly maintained. If you take good care of your battery, it may be able to last up to 5 years.

You may want to remove the cables and clean the connections periodically if there is any corrosion or build-up. You can use baking soda mixed with water and scrub any residue with a wire brush before wiping it down with a cloth.

Don’t forget to check the level of battery acid as well, depending on the battery type, so that it doesn’t get too low. Wear eye and skin protection to avoid getting any battery acid near sensitive areas of your body.

Whenever you unplug the battery cables, always wear gloves and remove the black cable (negative) side first before the red cable (positive side). Then replace the positive cable followed by the negative one, tightening both with a wrench.

#2 – Charging Batteries with 120 Volt Power

When camping in your RV at a campground with hookups, the electricity there will usually be 120 volts of alternating current (AC) power. This electricity will be used to power your appliances and RV systems, but it can also recharge RV batteries.

If you have a 120 volt AC outlet at home, you can also plug your RV into that to charge the batteries. Before charging though, make sure your RV has a power converter because the power from the outlet is 120 volts compared to the 12 needed for the RV’s systems.

When ready, just plug in the cable to your RV and wait. It can take hours to recharge if the battery is already severely depleted.

#3 – Solar Power Alternatives

Solar panels on the camper's roof

Another option for charging RV batteries is to capture the power of the sun. If you have solar panels, put them up on top of your RV and use a solar power system to convert the energy.

This is a great option for those who are boondocking or staying in primitive campsites that do not have electrical hookups. However, one of the drawbacks is that there is limited time in the day to capture the sun’s rays.

On a sunny day, a single solar panel can usually give about 3 to 5 amps of charge. The panels should face the sun directly and you may need to adjust the angles to be even more efficient.

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#4 – Using a Generator

Having a fuel-powered generator as a backup is a great idea when you don’t have access to electricity. Not only can the generator be used to power appliances, but it can also recharge the batteries if necessary.

Depending on the size of the generator, it can take time to charge the batteries. Still, it will give you enough charge if you need to perform a few tasks before you can find access to a stronger power supply.

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Monitoring RV Batteries

Monitoring RV batteries

To check how much charge is left in the battery, your RV may have a panel on the wall inside the coach to show the various levels.

You can also use a variety of hand-held devices to measure the voltage of your battery directly. A voltmeter can be placed directly on the probes of the battery’s terminals to see how much charge remains.

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If the battery was recently charged though, there might be a surface charge which will give an inaccurate reading. Just run some appliances for several minutes though to remove it and get a better readout.

Alternately, if a lot of appliances are running, this can also show the voltage as lower than it is. Turn everything off and wait for a short time to let the battery return to its internal voltage before checking the meter.

To extend the life of your deep-cycle battery, never let it go below 50% of its capacity. If you see the battery reaching this level, you should charge it as soon as possible.

Even if the appliances in the coach are turned off, they can still use minimal amounts of battery power, so don’t wait too long to recharge just because you aren’t using a lot of power.

#1 – How Charging a Battery Works

Because batteries store energy, in order to charge one, you need to feed it power, or current (amps). However, too much will damage the battery.

Empty or discharged batteries can take more current when you first start charging them. But the more charged they become, the less current they can take.

When full, batteries have about 12.7 volts. One that is low but still has enough power that is can safely be recharged will have around 11.6 volts. It’s important not to let the battery get below a certain amount of volts.

RV batteries will last longer if you always keep them above 12.0 volts but 12.1 volts is preferable.

The battery gets charged when another device gives it a lot of current and forces it to a higher voltage than the 12.7 it has when fully charged. To charge faster, force as much current as possible into it.

The charger you use must have a higher voltage than the battery you are charging to force more current into the battery. A charger with 13.5 volts will be able to do it but using something with 14.5 volts, for example, can force even more current.

After charging, the volt range of the battery may be higher than it’s fully charged state of 12.7 volts. It could be as high as 13 to 15 volts. But, after some time, it will return to its own voltage level.

#2 – Different States of Battery Charge

Based on how much a battery is charged, the voltage remaining will be different. The voltage decreases by 0.1 volts for each 10% decrease in the charge until 60% is reached.

The battery will start with a 100% charge and 12.7 volts and decrease as follows:

  • 90% charged – 12.6 volts
  • 80% charged – 12.5 volts
  • 70% charged – 12.4 volts
  • 60% charged – 12.3 volts
  • 50% charged – 12.1 volts
  • 40% charged – 11.9 volts
  • 30% charged – 11.8 volts
  • 20% charged – 11.7 volts
  • 10% charged – 11.5 volts

#3 – Undercharging, Overcharging and Equalizing Batteries

A lot of battery-related problems occur because batteries have been consistently undercharged. This can cause a battery to go dead as well.

When the battery is undercharged often enough, sulfation occurs. This can reduce the capacity of the battery or create a build-up between the plates inside, causing a short.

One way to correct this is through a process called equalizing. By raising the voltage very high for several hours, the battery acid starts to boil and the sulfate gets rubbed off the plates.

Be careful not to equalize gel or AGM batteries because it can only be done on wet cell (flooded) batteries that have thin plates filled with battery acid.

Overcharging isn’t usually a problem with RV batteries since most people don’t actually charge their batteries enough when recharging. However, it can cause the battery to lose water and the plates inside can get corroded.

#4 – The Importance of Charging Your RV Batteries

The majority of people will use their RV batteries for only a few hours a day or overnight to power air conditioning or heating. Many campgrounds have electrical hookups which do not cause you to rely solely on batteries.

But for those who enjoy the freedom of dry camping or boondocking without access to services and electricity, a battery is of vital importance. Keeping your batteries charged will mean a much more comfortable trip.

In addition to the comfort provided by air conditioning and heating, you’ll also be able to use the microwave and prevent food from spoiling should the refrigerator lose power.

For those who have RVs with slideouts, you will also need electricity to retract the slider when you want to drive to another location. Without a working battery, this will be impossible and may leave you stranded unless you have a generator to use instead.

#5 – How Long Does It Take to Charge RV Batteries?

It takes less time to deplete a battery than it does to charge it, so any time you recharge the battery, you’ll need a lot of patience. The amount of time it takes will depend on the kind of charger you have.

If you only have a converter, then it may only be able to charge at 3 to 5 amps which could take hours to recharge the battery. More expensive chargers can provide up to 30 amps of charging while others have over 100 amps capacity.

#6 – Problems with Dormant Batteries

To keep a battery in good working order, it should be used regularly and experience cycles of being used up, or discharged, and then charged. If left unused, the battery will eventually discharge completely.

It’s also inconvenient to be ready for a trip only to discover your RV’s batteries are dead, causing you to delay your travels.

Some may try to prevent this problem by leaving the RV perpetually plugged into power. While this will prevent the battery from discharging, it may still result in the battery not lasting as long because it still isn’t being used.

If you do want to leave the battery plugged in, use a charger that raises the voltage from time to time. Also, make sure to unplug from the power and run some of the appliances in the RV to use the batteries.

 Storing an RV Battery

RVs are usually put into storage over the winter and this can wreak havoc on their batteries and shorten their lifespan. If the RV is stored in a cold place, some batteries can freeze and die.

If you store your RV remotely, remove the batteries and take them home so you can store them nearby and in a well-ventilated and temperature-controlled area. Never put them close to a heat source, or they could explode. You’ll have access to monitor them once a month easily and charge them if they start to get depleted.

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Related Questions

Charge RV batteries

#1 – What’s the Difference Between a Car Battery and an RV Battery?

RV batteries are called “deep cycle” because they are made to provide a steady stream of power over a longer duration. They can also be discharged and then recharged multiple times.

Car batteries, on the other hand, are designed to give a lot of current over a shorter amount of time. A car’s battery is mostly used to give a quick burst of power to start the engine as compared to an RV which will run for a long time to power appliances while camping.

#2 – Can I Use a Car Battery in My RV?

Car batteries should never be used as a substitute for an RV battery. They are not designed for the same kind of usage, and a car battery will not be able to work the same. Always use a deep cycle battery that is meant to be used only in an RV.

#3 – Do I Need an Adapter to Charge My Battery?

Most RVs are either 30 or 50 amps. An easy way to tell is to look at the plug on your power cord and see how many prongs there are. Three prongs will indicate 30 amps while four prongs mean it is 50 amps.

If the campground you’re staying at only has one type of outlet, then you’ll need a converter to be able to use this power source to recharge your battery. Older campgrounds may only have 15 or 20 amps so you might need a separate adapter for those as well.

Product data was last updated on 2019-12-10 at 04:57.

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