What do you do if you don’t have shore power and your RV battery dies? Options are limited, but you likely have a vehicle battery and a pair of jumper cables to fix the problem. So just how do you charge an RV battery with jumper cables? This post will give you the answer.
Charging a 12V battery is a straightforward process that can be done in a few easy steps. Using jumper cables is one of the most affordable and convenient methods for charging your battery. All you need are basic supplies, like jump leads, an active car with an operational battery, and a few moments of your time.
Below are some basics before connecting batteries to your RV or vehicle battery.
Table of Contents
Deep Cycle or Starter Battery
When charging a vehicle battery to an RV, it is important to note that these are two different types of batteries. Your vehicle is likely a starter battery. And RV’s usually are deep cycle batteries. Both are most likely lead-acid battery, but their function and how they give power is quite different.
Starter batteries are designed to provide a large amount of electrical power quickly and over a short period of time. This makes them ideal for use in vehicles that need immediate energy, such as when you turn on the ignition or switch on your headlights.
Deep cycle batteries, on the other hand, are designed to provide less current but over a longer time – making them better suited for appliances requiring sustained power output.
These are typically used as marine batteries or recreational vehicles where they will be required to draw electricity from a steady source over several hours or days. Deep cycle batteries can also be recharged much more frequently than starter batteries due to their ability to withstand repetitive cycles without deteriorating efficiency.
Voltage
The good news is that both your car battery and trailer battery are 12V power. Where there are compatible, you can charge them by transferring power from one to another.
When you want to charge batteries, getting the right voltage is key. Knowing the right amount of volts to charge your battery is the first step toward a properly functioning system. Understanding the correct voltage is essential if you’re looking to charge a 12V battery.
When charging from one battery to another, the flow of power is from the higher voltage to the lower voltage battery. Typically, when it comes to charging 12V batteries, you will want between 13 and 14 volts of power.
When your vehicle runs, the alternator gives your battery a charge and keeps it at over 14 volts. That is great because you can easily transfer the power to a lower volt, like your dead (below 12v) trailer battery.
For more info on RV battery voltage, see 6v vs 12v RV Battery post.
Safety
When charging a battery with jumper cables, there are a few safety precautions that should always be taken.
It is also important to connect all clamps in their correct order, which is usually: red clamp on dead battery’s positive (+) terminal, black clamp on dead battery’s negative (-) terminal, red clamp on donor vehicle’s positive (+) terminal, and lastly black clamp on donor vehicle’s negative (-) terminal.
Jumper Cables
Jumper cables are electrical wires with metal clamps on each end that attach to the posts of two batteries. The positive (red) clamp is attached to your battery’s positive post, while the negative (black) clamp is connected to the battery’s negative post. An electrical current passes between the two batteries when all four clamps are connected.
If you find yourself without cables, ask around the campsite as you can usually find someone willing to share them and help out.
Charging RV Battery
If you decide to charge your RV battery with jumper cables, an important tip is to keep your good vehicle battery running.
First, make sure the battery terminals are clean on both batteries. They need to be clean so there is a good connection with the battery cable, and that power can be transferred from one battery to the next. If there is any corrosion or the terminal posts are not clean or shiny, you can get a wire brush, sandpaper, or even scratch the posts with a screwdriver to get to a good connection.
Secondly, keep your vehicle running while charging your RV. Without the constant added power from your vehicle alternator, the dead battery will soon take all the power and leave your starter battery as the dead battery. Your RV battery will take a while to take a charge as this power transfer is not immediate. Getting your dead battery to 12V or above could take a couple of hours, so that car will need to run that long (make sure you have enough gas!).
Finally, pay attention to the clamps and battery terminals. Make sure not to touch positive to negative, as this will create sparks and potentially cause damage.
Conclusion
Without shore power, your resources become limited when you need power for your trailer battery. With some jumper cables and safety in mind, using your car battery is a good option. Remember, keep your vehicle running, as you don’t want your starter battery to die down and cause another problem.
Tony is an avid camper and RV traveler. He fell in love with camping on his first RV trip with his wife over 25 years ago. Tony loves sharing lessons learned and tips about RV maintenance and safe traveling.