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How Long Does it Take to Charge my RV’s batteries?

The idea of RVing across the country has always appealed to me. When I was a child I lived many states away from my grandparents but that didn’t stop them from stopping by at least three or four times a year. Each time they would visit they would pull into our driveway with a big old motor home. It is something that has always stuck with me and something I hope to replicate when my wife and I are ready.

To prepare myself for future RV excursions I have been educating myself on the topic. If there is one thing I have learned over my life it is much easier to learn something if you attempt to teach it, or in this case, write about it. Research needs to be done. This research not only helps me learn but also allows me to create this article to hopefully help you as well. Today’s topic is focusing on RV and their batteries. Exactly how long will it take to charge your RV’s batteries up to full power? When should you charge these batteries? What can you expect?

How Long Does it Take?

Before we get into how long it will take to charge your batteries I first want to make the point that you should not let your batteries drain empty before charging. In fact, most folks recommend not letting them fall under fifty percent charge. During my reading I did find that some others stated that forty percent was as low as they were willing to go… but the consensus was fifty percent. To be safe though I would recommend staying at that fifty percent marker. There is a myth circling out there that you should not let the battery’s charge fall below eighty percent… but this is not true. You are fine until that fifty percent marker.

The batteries found within your RV are twelve volt. What a lot of folks do not know is that when fully charged these twelve volt batteries actually come in at 12.73 volts. The reason folks say to recharge when your batteries hit that fifty percent mark is when they reach this point they are now at 12.00 volts. If they fall under that fifty percent threshold their volts also fall under twelve volts. This could result in damage to the battery. An example of this type of damage is that if the battery is left at low charge or is completely drained for an extended period of time crystals can form on the plates of the battery. If these crystals remain without a recharge taking place then the battery is in essence ruined. This crystal forming process is called ‘Sulfation.’

Remember earlier how I said it was a fine line between the forty and fifty percent charge number? Well, it all boils down to how many volts your battery measures. If you are at twelve volts at a forty-five percent charge then you are OK. However, if you fall below that twelve volt threshold the a recharge is needed. “Volts on a battery can be measured by using a digital voltmeter. Set the tool to DC voltage and place the red lead on the positive terminal and the black lead on the negative terminal to read battery voltage.” (For more info on this, visit koa.com.)

Charging

The important thing to remember here is that there is no magic formula to discover how long it will take to recharge your batteries. There are just too many variables out there that can impact the length it takes to charge. A couple of examples of these variables are:

  1. How low is the charge on the batteries? Obviously it is going to take a shorter amount of time to charge your batteries if they are at seventy percent versus at forty percent.
  2. What else do you have running in your RV that is drawing power? It could be lights, refrigerator, electronics, or anything else. All of these require power and will draw power away from your batteries that need charging. Some folks go as far as switching their power inverter off to prevent any further power draw.
  3. Another big question is exactly HOW are you charging your batteries? There are a variety of ways to do this. We have provided a short list of these options below. They are ranked by the most recommended choice.
    1. Using your vehicle’s engine and alternator.
    2. Connecting to a shore power source at a camp-site. Typically a thirty or fifty amp plug-in.
    3. Connecting to a solar power generator.
    4. Connecting to a built-in or portable generator. Typically a thirty or fifty amp plug-in.
    5. Using an automotive battery charger
    6. Worst case, jumper cables.
  4. Each of the examples above can have different charge rates. The alternator in your RV can send a different amount then a generator can. In many cases generators can be bottle-necked based on the amperage limit of your converter. The converter is what converts the AC energy over to DC energy so your batteries can be charged.

With all of these variables in mind it is impossible to predict exactly how long it is going to take to charge your batteries. That being said we can still do our best here to provide you with an estimate, but it is only an estimate. Now most folks recommend charging your motor home’s batteries when they reach fifty percent charge. With that fifty percent charge in mind we can say that it will take anywhere from four hours all the way up to seven hours. If your battery is below that fifty percent threshold then you could be looking at ten hours or more to fully charge the batteries.

You can speed this charge rate up by reducing the number of things drawing power. Like we mentioned previously, turn off the lights. Turn off anything that is not absolutely necessary. The more you reduce the more power that is able to go towards charging your batteries. An important point to remember here is that batteries drain faster then you can charge them. So, if you have an excessive amount of power demand coming from your recreational vehicle AND you are trying to charge your batteries you may find that it very slow going. This is why many folks opt to charge their batteries overnight as there is much less demand.

From my research I have found that the most recommended approach is to charge your batteries via the vehicle’s engine and alternator. After all, it is a vehicle that you are charging so it would make sense that the tried and tested method that all of our vehicles use everyday would be the standard recommendation. That being said, it is not a recommend if you are camping as you do not want to idle for that long. This is where a generator or shore power connection would come in handy. Some folks swear by using an automotive battery charger, but I would advise against them unless you are in a desperate need.

Often times folks will stop charging once they reach a ninety percent charge. This is done as the amount of time it can take to charge from ninety to one-hundred percent can be significant. Experiment on your own setup but you may be able to reduce the amount of charge time by charging to ninety percent and calling it good. The last point to mention here is that faster is NOT better. A slow and steady charge is best for your batteries, if you rush it, or purchase products that promise a super-fast charge then be weary. If you charge these batteries too fast you could end up permanently damaging the battery.

Conclusion

Like with many things folks there is no clear-cut answer here. There are so many variables that have to be considered that it is difficult to gauge what you and your system’s needs are. The best way to do this is to go out there and try it for yourself. In many cases a controlled trial and error experiment is the best way to discover what is needed. When I say controlled I mean have a back-up plan ready in case something does go wrong. After a few experiments you should have a good idea of what it takes to charge your unit and this will allow you to plan your future camping trips with ease.

I hope this article was helpful and able to answer some of your questions. For some more reading on the topic I suggest visiting a few of the links below:

Thanks for reading,

Alec Johnson

ToughAssTools.com

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