How to Charge RV Batteries?

RVing across the country has always been a dream of mine. I am still quite a ways out from achieving that dream but I know that I will eventually get there. For those of you who are lucky enough to already be doing this I envy you. The world is open to you. All it takes is pointing to a map and driving. The freedom of it is enticing. Like with many things though it is not all fun and games. There are still many questions and topics to learn when it comes to caring, maintaining, and enjoying your recreational vehicle.

In today’s article we are going to take an in-depth look at one of these topics: Batteries. As you know your RV, or motor-home, comes with a battery or batteries. These batteries store direct current energy that power everything in your RV. This includes the lights, the radio, the refrigerator, and even your furnace. Without your batteries your RV loses all of its creature comforts. This is why it is so critical to watch the charge on your batteries and to ensure that they do not get to low. Most people recommend not letting the charge on your batteries drop below fifty percent. When your batteries do drop to that fifty percent threshold you need to know HOW to charge the batteries back up to ninety or one-hundred percent. Let’s take a look.

How to Charge the RV Batteries

RVs, or motor homes, can come with one battery or multiple. Along with that their location can vary by make and model. If you do not know where your batteries are stored please consult your owner’s manual, call a dealership, or worst case canvas around the outside of the vehicle until you determine where they are. Once you have found them then we can begin to look at how to charge them.

To understand how to charge your batteries we must first look at the various ways that your battery can be charged. Throughout my research I have found that there are four main ways to charge the battery. Now as I list these I am going to rank them from best to worst. Some of you may disagree with this ranking, but I believe it is well sourced.

  1. The RV’s Alternator
  2. Shore Power
  3. Generators – Built-Ins & Portable
  4. Solar Power

RV’s Alternator

The most common way to charge your RV’s batteries is the old-fashioned way by using the engine and the alternator. This is the way every vehicle on the road today produces power. The engine creates mechanical force which is converted over to electrical energy by the alternator. In essence your RV, or motor home, is no different then that of a standard car. They both have engines and alternators. The only real difference that you are going to see is that the size and number of batteries. The overall process remains the same.

Using the RV’s alternator to recharge your batteries is widely regarded as the best and most efficient. The alternator produces energy but it also produces direct current (DC) energy which is the exact same type of energy that is stored in your batteries. If you were to recharge your batteries using shore power or a generator then you would have to convert their alternating current (AC) power over to DC power by using a converter. With an alternator you get the DC energy upfront.

When charging your batteries with the alternator it is important to remember that the appliances and electronics that you have on during this time all consume battery power. The engine’s alternator provides DC power which is stored into the battery. This DC power is then converted to AC power using an inverter. The AC power is then used to power your air conditioner, furnace, refrigerator, etc. If you have too many appliances on you could actually end up draining your battery even while your engine in is running. This is why it is important to have most of these off during charging with your alternator. Many people will just turn their inverter off to prevent any battery drain. If you do choose to have appliances on during this time watch your battery’s charge percentage to ensure that it is not only moving upwards but it is at the right amount of speed. If it charging very slowly it may be time to turn off some appliances.

Like with anything, there are downsides to using the alternator charge method. The first is it can take a significant amount of time to get back up to full charge. If your battery is below forty percent you could be looking at eight, nine, or even ten hours to get a full charge. That eight hour window may not seem so bad if you are already on the road and are planning on a long road trip… but if you are staying still at a camp-site for a couple of days then you definitely do NOT want to idle your vehicle for eight hours at a time. So, while using the alternator is one of the most efficient ways to charge your batteries it is not ideal for everyone.

Shore Power

If you are going to be staying put at a camp-site or RV park then charging your batteries with your alternator is not an option for you. I know that you do not want to idle for hours on end and none of your camp site neighbors want that either. Now depending on the park you have chosen they can have what is known as ‘Shore Power.’ Shore power is just the RV term for a power source at one of these camp-sites.

If the camp site does have power it will either be a thirty or fifty amp outlet. The thirty amps are for smaller to medium sized motor homes whereas the fifty amp is for the larger models. Either way, it is a straight power source that will give you all the energy you need to power everything within the RV. This could be your furnace, air conditioner, refrigerator, computer, phones, coffee maker, and whatever other creature comforts that you have with you. NOTE that you can also hook your RV up to your home using a fifteen or twenty amp power outlet. This may take some configuration of your circuit board depending on your home.

The best part is that when you connect to these shore power systems your batteries will automatically begin to recharge themselves. This is done by converting the alternating current (AC) energy that you are receiving from the camp site over to direct current (DC) energy. This DC energy is then stored in your batteries. The downside when using shore power connection is that your charge to the batteries is limited by the capacity of your converter.

As we discussed earlier, the shore power connection gives you access to AC energy, but if your batteries hope to store that energy it needs to be converted over to DC energy. This is where your RV’s built-in converter comes into play. This is also where a possible bottle neck can occur. Your converter has a limitation of how many watts it can transfer from AC to DC at a time. The lower the limitation the longer the charge will take. You are essentially getting unlimited power from the shore connection but if your converter is bottle necked then you could still be looking at long recharge times.

As an example, if your battery’s charge is below fifty percent then you could be looking at over eight hours of charging to get you back up to one-hundred percent. Now, if you are staying at the camp site for a while this might not be a problem. This holds true if you are spending the night. Your batteries will charge overnight and there is no inconvenience. If that eight hour charge time proves to be too long there is another option. You can upgrade your converter. There are converter overhaul kits out there that when done can shrink that charge time down to just a couple of hours. One such example of these can be found on Amazon or by clicking here. Be aware though that these kits can cost upwards to three-hundred dollars. It is up to you if you want to invest to save the time or just wait it out each night for a full recharge in the morning.

Generators – Built-Ins & Portables

Generators rather they be built-in to your RV or are an outside portable unit work much the same as a shore power connection does. They provide alternating current (AC) power and have a thirty amp plug-in that allows you to connect your RV directly. Many motor homes nowadays come with built-in generators. These come in handy as you do not have to do any setup. They are already connected to your RV’s power system and they most likely already use fuel that is built in as well. Depending on the built-in they could use their own propane tank or they could use the same diesel/gasoline that your RV uses for its engine. They are also much quieter then a standard portable generator as they are shielded by an outside compartment in your RV which acts to muffle the noise.

The problem with built-in generators is that they come with the RV during the manufacturing process. What this means is that the built-in RV generator typically only comes with enough energy to power all of the stock features of your motor home. If your RV does not come with an air conditioner and you decided to purchase one then chances are you are going to exceed the wattage limit of your built-in generator. The same example can be said if you try to plug-in a bunch of extra appliances like a coffee maker, microwave, hair dryer, or computers. All of these require power and all of these add to your total power required.

If you are exceeding the power of your built-in generator you have a couple of options. The first is to find an alternative built-in generator that provides more power, that will fit in the same compartment, and that will connect properly. This can be easier said then done. Do some research yourself and also contact the dealer where you purchased the RV from. Chances are they do have recommended generators for power upgrades. The downside here is that this can be expensive. Most things are when going through dealerships. Trust me on this, as I have many years of experience working with dealerships.

The other option here is to go with a portable generator. The same can be said if your RV doesn’t even come with a built-in generator. Portable generators provide the same purpose and also have a variety of benefits over built-ins. Portable generators can be any size you want them to be. You can find some starting at around one-thousand watts all the way up to twelve or even fifteen-thousand watts. You will not want for power. They hook up just like your shore power or your built-in generator connection. You’ll also find that they are significantly cheaper then a built-in model. Our recommended portable RV generator is this model from Durostar. It provides over three-thousand watts and should be enough power for most applications.

The downsides here is that portable generators can be rather bulky, especially the higher up in wattage you go. In some cases they can easily be over one-hundred pounds. The good news is that these larger sizes do come with wheels. It will still be a burden though to haul one of these around with you during each camping trip. Another big downside of the portable solution is the overall noise they produce. In many cases camp sites have quiet areas or quiet times. These are times where portable generators cannot be run. This is done in an effort to preserve the serenity and nature of the camp site.  Some portable generator models can have decibel levels ranging from seventy to as high as one-hundred. They can be as loud as a lawn mower running next to you.

If noise is a problem for you there is an alternative portable type known as an inverter generator. These inverter generators are known to be super quiet. They have a decibel range between fifty to sixty. That can be similar to the sound of rainfall on the low end and about the sound of a dishwasher running on the high end. They are much quieter then your standard portable models. The downside to these inverter units though is their cost. Inverter generators can be significantly more expensive then standard portable units. Our typical recommended inverter generator is this model from Champion. It provides over three-thousand watts… but as you can see you are paying a premium for it.

Another important factor to consider is that when going with a portable generator over a built-in you need to consider what fuel source you will need. I mentioned earlier that lugging these generators around can be a hassle, especially on the larger models… well now you have to haul some fuel with you on top of the generator. The portable models will not use the same fuel that is built into your RV. Generators can handle a variety of fuel sources rather it be propane, gasoline, or diesel. Typically I like to recommend diesel as it is the most efficient and cleanest burning. Whatever fuel you decide on you should look at how long a gallon of fuel will last for your generator. This will give you an idea of how much fuel you need to have stored.

The last thing to mention when looking at portable generators is the size of the generator that you will need. If you purchase a size too small then you are not going to be able to power everything you wish. If you purchase something too large then you are going to be wasting power and fuel. Finding the right size is key. I wrote a separate article on sizing generators for your RVs which can be found by clicking here. I highly suggest reading through this article to ensure that you are buying the right sized generator for you and your RV.

Solar & Wind Power

Over the years solar power has become more and more popular. It is a green an energy efficient way to produce power. It also allows you to go truly off-grid when boon-docking. If you think about it even when you are relying on generators you are still reliant on having a constant fuel source of gasoline, diesel, or propane. With a solar system all you need is the sun. It truly gives you freedom to live that off-grid lifestyle.

These systems come with a set of solar panels which then feeds into what is known as an ‘Amp Controller.’ These are also called ‘Charge Controllers.’ These controllers prevent your batteries from overcharging. For those of you who do not know, overcharging can completely ruin your battery, so it is a good protection to have. When purchasing a solar system there are two types of controllers to choose from. The first is known as pulse width modulation charge controller (PWM) and the second is maximum power point tracking charge controller (MPPT). The MPPT is more efficient and the better choice over the two but it is more expensive, so it is a matter of preference.

Along with choosing what type of charge controller you want you also need to figure out what size charge controller  you need for your application. These sizes, or power levels, are calculated in amps. To successfully charge your batteries using solar power you need to ensure your charge controller has more amps then your solar panels and battery combined. To determine this all you need to do is divide the watts of your solar panel by the number of volts in your batteries. So, for an example let’s say you have 1 twelve volt battery and 100 watts solar panel. The formula becomes 100 watts / 12 volts = 8.33. So, by using that 8.33 number we know that our charge controller has to have amperage of 9 or above. If you had 2 twelve volt batteries then you would multiple the twelve volts to get a number of twenty-four volts and so on and so on.

While the 9 amp charge controller will get the job done in the above example it may be worth your time to invest in a larger charge controller in case you want to increase the wattage of your solar panel down the road. I’ve always been a firm believer that it is better to buy bigger with room to expand then to buy the smallest size and have to end up buying it all over again when it does come time to expand. In this example solar kit from Amazon we can see that it comes with one-hundred watt solar panels and a thirty amp charge controller. This gives you plenty of room to expand your solar panels if you wish to down the road.

There are even some folks out there that have opted for using wind turbines to power their motor-homes. These wind turbines work the same as the solar system. They come with a charge controller as well. The only real difference is that the turbine needs to be setup and they are NOT meant for travelling. Wind turbine power is something I would recommend if your RV is mostly stationary on your land. They are not legal to operate while driving and it can be a hassle to have to set them up each time you stop. This is why it makes the most sense if you are living out of your RV on your land. You also need to ensure that you have enough wind to support it.

Jumper Cables

Yes, yes I know I stated that there were only four ways to charge your batteries. The only reason I put it that way folks is that charging your battery with jumper cables  is not ideal. These are emergency measures if your battery is completely dead. If you do run into this situation you can jump charge your battery much the same way you would with any other vehicle. Park another vehicle close enough to your RV’s batteries where you can safely connect jumper cables. Connect the cables like normal, turn the vehicle on, and let the battery charge.

One thing to keep in mind here is that you should turn off ALL accessories on the RV. This means appliances, electronics, and even your inverter. Turn it all off as you do not want something draining your battery’s power while you are trying to jump it. Once you have the battery charged to a point where it is no longer dead then I recommend moving towards a more traditional charging method rather it be using the RV’s alternator, shore power, generator, or something else.

These traditional methods are tried and true and are best for your RV’s batteries. After all, if this was  regular vehicle you do not charge the batteries all the way to full when jumping your car. No, you give it enough juice from the other vehicle so that you can turn the thing on. Once it is on the alternator takes over and you are good to go. The same principle applies here. Get that initial charge and then move towards a more stable method.

Surge Protectors

Power spikes can be a problem rather you are using shore power, generators, solar power, or anything else. These power spikes can occur randomly and without warning. If left unchecked they can end up damaging the appliances and electronics within your RV. To protect against these power surges it is recommended that you insert a ‘Surge Guard’ between the power intake and your RV. This surge guard prevents the power spikes by only allowing continuous power into your RV. It acts as a guard or stopper and catches those power spikes before they get to your RV. Here at ToughAssTools we recommend this Surge Guard on Amazon. It has nearly five-hundred reviews with the majority being positive.


Well folks I believe we have covered nearly everything there is to know about charging your RV’s batteries. Overall, it is not too complex of a process if you stay on it. Just be sure to watch the charge percentage of your batteries and ensure that you do not drop below that fifty percent threshold. If you do find yourself dropping below fifty you should be OK in that forty to fifty percent range, although it is not ideal. Any lower and you can risk damaging the battery.

One more point I wanted to mention in this before closing the article is that in many cases it can take a significant amount of charge time to go from ninety percent to one-hundred percent charge. If you are pressed for time or just want to move on and not worry about charging you will be fine with that ninety percent number. It will save you time and still get the job done for you.

If you are still hungry for more information on this topic  than  I highly recommend the below articles from other websites. These links helped me a lot when researching for this article.

Thanks for reading,

Alec Johnson

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