Can a Car or 12v Battery Shock Me?

Have you ever looked down at that 40-pound car battery and wondered if it could shock you if you were to touch both terminals?

If you’re new to working with 12-volt batteries for your battery bank (car, marine, golf cart), it’s a completely normal question to have.

I generally have a motto in life that if something can hurt or kill me and I can’t see it, that that thing needs to be respected.  Electricity definitely falls into that category.

A person’s skin offers greater resistance than the voltage of a car battery and therefore it will not be able to shock or kill by simply touching both terminals with bare hands.  Car batteries are riskier from explosions and poisonous gasses rather than electrical shock.

Why doesn’t a car battery shock and kill me?

By itself, a standard car, marine, or golf cart battery will store a lot of energy and certainly has the amps needed, but transferring that energy through your skin and body to a ground point is the problem. 

The problem lies in the number of volts behind the 12-volt battery.  

Volts represent the pressure being placed upon the electrons within the battery as they try to flow out from the negative terminal to the positive terminal in a complete circuit.  At 12-volts, the epidermis (skin) of the human body simply has a higher resistance than what the battery can deliver as far as the pressure behind the current of electrons.

With greater resistance in the skin, the current cannot flow and no sensation is felt.

Think of a 6’5” bouncer of a club who wants to knock you out.  He’s certainly got the muscle power to do it (pressure behind the punch, aka volts), and he’s got the massive fist to do it (surface area and mass, aka amps).  The combination of these would deliver enough watts to accomplish the task (volts x amps = watts).

Now, imagine that same 6’5” bouncer, with the same size, but he recently had a stroke and can barely lift his punching fist enough to feed himself.  

He still has the massive fist (amps) to knock you out, but the pressure behind the punch is negligible and you would be able to take any punch thrown your way and likely not even notice the contact.

The same can be said of your car battery.  This is not to say that your battery can’t sometimes mess with you if you set up the perfect conditions.

If you were extremely sweaty and wearing wet clothes, it’s possible that you could receive a little bit of an electrical sensation as the salt water becomes a conductor of the electrical current.  In a healthy person, this would not be fatal and wouldn’t cause any damage.

So, is a 12-volt battery harmless?

No. This couldn’t be farther from the truth. Though the risk of electrical shock from touching the terminals of a 12-volt battery by hand is negligible and not harmful, the inhalation of poisonous gases or creating a short with metal between the terminals which would result in an explosion is a very real possibility.

Poisonous Gases

Without adequate ventilation, a defective charger or simply an overcharge of a battery (controlled or otherwise) can result in hydrogen gases (explosive) and hydrogen sulfide (poisonous) being released in the surrounding environment.  

With a single battery and in a normal environment, the risk is low of being poisoned to death by breathing in hydrogen sulfide is extremely low, but if you smell rotten eggs when conducting a desulfation/equalization of your battery bank, know that you’re releasing that gas into the air.  

Your nose will become desensitized to the smell after a short time, so just remember that you might still be exposed even if you stop smelling it.

Prolonged exposure to hydrogen sulfide in a bedroom, for instance, can result in throat and lung irritation that can last for days.

Hydrogen gases can be released due to a damaged battery or during charging and over-charging processes.  

The amount released won’t kill you to breathe in, but if confined in a small enough area without ventilation, the simplest of sparks or flames can cause an instant explosion with lots of sulfuric acid going in every direction.  Property damage and death are a very real possibility if this occurs.

The two primary ways to prevent problems with battery gases is to always allow for proper ventilation when charging and to not conduct a controlled overcharge (equalization/desulfation) indoors.  

Many chargers, like the Schumacher brand, will automatically attempt to desulfate your battery upon startup. This process can take 8-10 hours and will release lots of gases as it performs a controlled overcharge of your battery.  

If you are looking to charge your batteries indoors, I highly recommend this one from Amazon. I’ve used it every day, 24 hours a day, for over 6 years without fail on my battery bank and also to top off my car batteries every month. It is a gentle charge and I’ve never experienced any noticeable off-gassing from it or excessive bubbling. It’s easy to connect, safe, and reliable.

For more details on how to do this safely, feel free to visit my article here on charging and storing your 12-volt battery indoors to avoid any beginner mistakes!

Creating a short/Bridging the terminals

The bridging of a piece of metal (a wire, or non-insulated tool) can be a near-instant killer as well.  Though the battery lacks the volts to overcome the resistance provided by your skin, the metal in a tool or wire is no match.  

Accidentally placing a tool or a wire on a battery can turn it glowing-red instantly and sometimes weld itself to the battery nearly instantaneously if allowed to touch both terminals.  The extreme amount of heat, sparks, or fire will soon join with the explosive hydrogen gas and you might not have any more earthly problems after that. If you do survive it, you’re sure to have a lot of problems.  

Can battery Acid Hurt Me?

Yes, battery acid can hurt you if it comes into contact with your skin and if it is not immediately washed away with water for several minutes.  The length of time it is in contact with skin is the primary factor in the severity of the burn. When working with 12-volt batteries, always wear eye and hand protection.  

Battery acid is an electrolyte and the primary component that burns you is the sulfuric acid.  A minor splash or a few drops will certainly burn your skin if left untreated, but if you run water over the affected area for a few minutes you should have nothing more than a little pink and irritated skin.  

Even a pinhead-sized drop will eat a hole in your clothes, so only wear clothes that you won’t miss when working with batteries, and always have a bucket of fresh water nearby to dunk your arms or face in if you happen to get a splash of acid on you.  

Rubber gloves are a must, as are safety glasses or goggles.  

To safely add distilled water to a flooded lead-acid battery (typical of those found in most cars), I recommend using a syringe, like those used to give babies their medicine. It might take a little longer to add the water, but it is safer and more precise.  You will all but eliminate the spills that could potentially burn you or ruin property.

For more info on how to safely handle 12-volt batteries, you can check out my article here on storing and charging 12-volt batteries indoors for a DIY battery bank.

Robert Van Nuck

Robert lives in central Michigan and enjoys running, woodworking, and fixing up small engines.

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