How Does A RV Battery Isolator Work

When you first get your RV, there will be many buttons, settings, and things that may make you confused about what they do. It is important to know how each system in your RV works, with the battery isolator easily one of the most important systems that you need to check on.

A battery isolator is used in most RVs and motorhomes; it isolates the batteries from each other inside the vehicles, ensuring there is always power to start the engine. The battery isolator will ensure that the power inside the RV for your electronics does not draw power from the engine battery.

Many people are confused about why these are important, especially those who convert their fans, causing them to end up powerless far away from civilization.



What Is An RV Battery Isolator?

Simply put, the battery isolator is a set of cables that connects the batteries in the RV to the alternator without connecting them to each other. Usually, the isolator will be installed in the engine compartment and should only take a few minutes to install properly.

While extremely modern RVs will have sensors on their battery isolators, most battery isolators are completely passive systems. This means that once installed properly; you will never have to worry about them again, not even when you might be adding more batteries to the RV.

This is often why people are shocked to hear that their RVs may not have battery isolators or that something has gone wrong with the wiring. Fortunately, battery isolators are usually made to fail in such a way that it will discharge the less important battery, allowing you to still drive to a workshop.



Why Is The RV Battery Isolator Important?

While your solar power array and the batteries in your RV are certainly strong enough to power your electronics, there is still a small downward slide. This means that unless you are linked up to a wall somewhere, the amount of power you are using will be more than can be supplied by the sun.

The electronics in most RVs are fully connected with each other, with the alternator in your engine providing too much power actually to charge the engine battery. This is why you connect the alternator to the battery that powers the electronics of your RV as well, to charge them.

However, this would normally create a connection between your RV battery and the engine battery, causing you to drain the engine battery. The battery isolator isolates the engine battery, allowing power to flow into it from the alternator, but stopping it from being used for the RV electronics.



How Do You Know When The Battery Isolator Is Working?

There is one way of testing if your battery isolator is working; you will need to have a specific tool to measure how well it works. You will need to get an electric meter, one that can be used to measure the flow of power in ohms or another way to test the effectiveness of the battery isolator.

Start by disconnecting the two positive connections you will see on the battery isolator, taking care not to touch any metal or the ground. Placing your meter on these two connectors, set it to ohm and start to measure the power; it should be reading zero ohms.

When this is reading zero ohms, it means that these two are running on a separate circuit and are not running together. It should be noted that these are the two outgoing connections for the battery isolator, with the incoming power coming from the alternator.



What Are The Steps To Installing An RV Battery Isolator?

Many people immediately start stressing when they are building or converting an RV of their own and have to work on anything related to the engine. However, installing the battery isolator or simply checking on it is one of the simplest things you can do and should only take a few minutes.

However, several steps will still need to be followed as there are a few cables that you need to learn to identify and know how your isolator works. If installed correctly, you may never have to worry about the battery isolator ever again.

  • Location: You will need to install the battery isolator inside the engine compartment, preferably close to the battery. This will allow you to use the existing cable from the battery and to add the new cables without too much of a headache.
  • Connection: Once you have the battery isolator mounted next to the battery, you need to connect everything. You will need to remove the positive battery terminal and put it on the incoming port for the isolator, reconnecting the battery with one of the outgoing terminals.
  • Cables: We are lifting this out because most people make the mistake of assuming that any cables will do the job. If you are buying a new isolator, the included cables should be the only ones you are using; however, if you have a reused one, you need to ensure that cables can handle the high amperage.
  • Crimping: Your wires will also need to be tightened; this is a step we include to remind you that a cable simply resting or being twisted around a port is not secure enough.
  • Testing: Once you have fully installed the battery isolator, test everything out and make sure they work properly. To do this, you will need to start the engine and make sure that everything is charged, using your power meter to test the flow of power.


How Long Does It Take To Charge A Battery When Using A Battery Isolator?

A common question can be extremely complicated to answer as several things affect the overall speed at which your battery will charge. The battery isolator splits the power more or less equally between your batteries, ensuring that both get enough to stay fully charged.

However, the size of your batteries, the size of the alternator, and the speed you are driving will greatly affect the overall speed at which everything is charged. Generally, if you are driving down a highway for more than two hours, your batteries will be nearing a full charge.

This is because vans and RVs have large alternators that can easily and comfortably charge up most batteries with power to spare. This is why it is always a good idea to drive further between camping locations, as it will help keep everything charged and ready.


Your RV needs to have a battery isolator to ensure that all the batteries are running so that they are comfortable. The power draw from just camping for a night or two can be much more than you imagine; the last thing you would need while camping is being unable to start the engine.

Whatever you do, please don’t think of your engine battery as the backup battery for your accessories!

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