A common concern is that jumping a car in the rain might be a dangerous activity. That’s because doing anything with electricity around water seems like a bad idea. So, let’s settle this right now with a definitive answer.
Jumping a car battery in the rain does not pose any additional danger to you and is just as safe as on a sunny day. Car batteries operate using a 12-volt DC power, meaning the voltage is too low to cause you physical harm. Hooking up the connectors incorrectly is the only real threat to worry about.
Jumping a car is a relatively safe action when the directions are followed correctly. There are some excellent tips to follow to keep yourself and other road users safe when jumping a car in the rain.
Why is it Safe to Jump a Car in the Rain?
The fear of doing anything electrical in the rain is related to the dangers of electrocution. These fears, in most instances, are valid. In the case of jumping a car during a downpour, however, the risks are negligible as car batteries only run on 12 volts.
Of course, biological damage from electricity isn’t limited to the voltage applied; it is also down to how many amps of current you are exposed to. Luckily, humans have quite a bit of resistance, so the current will be low. Ohm’s law explains why 12 volts won’t harm you.
Ohm’s law: Voltage = current x resistance
If we rearrange that equation, we can see that:
Current = voltage/resistance
Humans can have up to 10,000 ohms of resistance, though this can be as few as 1,000 ohms when wet. Since we are dealing with a rain scenario, let’s assume we are drenched and will have the lowest resistance possible. The maximum current we can expect to experience from a 12-volt battery is 12/1,000 = 0.012 amps or 12 milliamps. Granted, this can hurt you, but this is tenfold less than a lethal dose.
Above is the worst-case scenario, where it is assumed you are submerged in water. This is unlikely! Fortuitously, receiving a shock of any kind is improbable if you follow the correct procedure for jumping a car. To maintain your naturally high resistance, keep your hands and the metallic connectors of the cables as dry as you can. By doing so, the severity of a shock will be minimalized.
Is it Safe to Jump a Car in a Thunderstorm?
While rain may seem benign, what about a severe rainstorm or even a thunderstorm with thunder and lightning? Both excessive downpours and lightning pose additional dangers to jumping your car.
Low Visibility is the Biggest Concern
A hard downpour usually results in a loss of natural light and reduced visibility on the roads. Fortunately, car batteries fail when the engine has been turned off in locations such as driveways or designated parking spots. Therefore, it is unlikely that you will be attempting to jump a car near fast-moving traffic.
Despite this, if you are jumping a car when visibility is limited, do your best to make yourself and your vehicle visible. Take actions such as placing reflective cones on the road and ensuring both cars have their hazard lights on (when the jumped car can).
I’m surprised more car emergency kits don’t come with decent emergency cones or lighting. I recommend that you pick up some LED road flares, like these found on Amazon, to keep in your trunk for the car problems that are bound to happen to everyone.
Also, if you own anything reflective or bright, have it in your vehicle so you can wear it on occasions such as these. Also, do your best not to be wearing all dark clothes, as this makes you nearly invisible in dark conditions. By taking these actions, you have reduced the chance of an accident.
What About Lightning?
Lightning does complicate the safety of jumping a car. If you can wait until the thunderstorm passes, that is the recommended course of action. There is no sense in risking your life. However, if you must proceed, then there are some things to be aware of.
It’s a myth that the rubber in your tires is what protects you during a lightning strike. Your safety emanates from the metal on the roof and sides of your car. The metallic frame creates a makeshift Faraday cage around you, keeping the electricity away from the interior of the vehicle. As a result, the voltage goes around the car to the ground.
If you are touching the metallic parts of the jumper cables during a lightning strike, you will be part of the circuit. You will receive a shock. Whether or not the lightning strike will kill you depends on the electricity’s path to ground. Seeing as a bolt of lightning can carry between a million to a billion volts, you could expect to receive a lethal dose of current. Once you consider this, recharging that car battery can probably wait.
How to Safely Jump a Car Battery
Regardless of the weather, to stay safe, you need to jump a car correctly to avoid receiving a shock, destroy the battery, and for the procedure to work. Luckily, it is a straightforward process!
- Start with both cars turned off.
- Attach one end of the red cable to the positive post of the dead battery.
- Attach the other end of the red cable to the positive post on the good battery.
- Next, take the black cable and attach an end to the negative post of the good battery.
- Connect the other end of the black cable to a larger metallic, uncoated part of the engine block in the dead battery’s car. Do not attach it to the battery.
- Start the car with the good battery.
- Start the car with the bad battery and leave it running.
- Disconnect the cables in reverse order (bad battery black, good battery black, good battery red, bad battery red).
- Leave the dead battery car on or drive it for 30 minutes to give the alternator time to recharge the battery.
When doing this in the rain, there are a few extra precautions you can take to ensure your safety. Do your best to keep raindrops off the battery and the cables. While there isn’t likely to be any danger of the cables shorting, affecting the battery, or producing a spark, it is best to exist on the side of caution.
The main issue is getting the rest of your engine wet. However, in a typical downpour, it is unlikely you’ll get the engine any wetter than you usually get from water splashing up through the undercarriage from driving through puddles. To keep things under the hood dry, though, try not to lift your hood higher than it needs to be to attach the cables. If possible, use an umbrella or your jacket to create a dry environment.
Once you can, allow the engine to dry to prevent any corrosion. You can do this inside a garage, for example.
Jumping a car battery is a relatively safe process, provided you follow the correct procedure. As car batteries run on a low voltage (12 volts), there is no danger of life-threatening electrocution from jumping a car in the rain. In severe weather, however, do ensure you and the vehicles are highly visible to other motorists to avoid accidents and try to keep the engine as dry as possible.
Does Revving the Engine Charge a Battery Faster? Yes, revving your engine will charge a car battery faster. When you rev the engine, the crankshaft turns, which turns the belt that is connected to the alternator. The alternator then turns and produces electricity, powering all the electrics in your car and recharging the battery simultaneously. As everything in this process is connected, the harder your engine works, the faster the battery will charge.
How Do I Know What Size Battery My Car Needs? Car batteries are available in different physical sizes and are designed to deliver various currents. These pieces of vital information are available on your current battery’s label or should be noted in your car’s owner’s manual. To get the correct size, look for the group size. This number covers the dimensions of the battery (height, width, and depth) as well as the post-placement (side, top, positive, and negative posts). By matching this number, you will get a battery that will fit in the battery compartment of your vehicle. The second number is the cold crank amps (CCA). Make sure you buy a battery with at least this same rating, if not higher. If you live in a cold climate, your car will perform better with a CCA. For most vehicles, a battery with a CCA of 600-700 is suitable.
Is Water a Good Conductor of Electricity? Water can be both an excellent conductor and an excellent insulator of electricity, depending on its purity. Distilled water (condensed from steam) or deionized water only contains hydrogen and oxygen atoms. There are no free ions to allow the electricity to move through the liquid. This makes pure water a perfect insulator. In contrast, rain, tap, sea, and bottled water contain many charged ions coming from dissolved calcium chloride, sodium chloride (table salt), magnesium chloride, etc. It is through these free ions that electricity can move through water readily.
For more, don’t miss 20 Car Emergency Kit Essentials | You Must Carry These Items.
Hey, I’m Jim, and the author of this website. I have always been interested in survival, fishing, camping, and anything in nature. In fact, while growing up, I spent more time on the water than on land! I am also a best-selling author and have a degree in History, Anthropology, and Music. I hope you find value in the articles on this website. Feel free to contact me if you have any questions or input!