Is it Safe to Charge a Car Battery Indoors?

If you are a DIY sort of person, you have probably already dealt with charging your vehicle’s battery when it goes dead. It is an entirely common problem and one that every driver should know how to handle.

Unfortunately Mother Nature sometimes conspires against us or we might live in a setting where we cannot leave our battery or charger outside on the street; we’ll have to bring it inside.

Is it safe to charge a car battery indoors? Yes, it generally is, so long as you follow some basic precautions, and use the correct charger with proper settings for your battery. In-home charging safety protocols are simple and easy to implement, and assuming you’re not attempting to charge in an environmentally sealed room, or charging many batteries at once, you should not have anything to worry about.

As always, recharging powerful batteries and messing with energized equipment warrants a thorough safety briefing. We’ll provide you with tips and other cautionary items below to help you charge your battery inside safely and quickly.

Ventilation

One of the most important items you should consider when charging a car battery inside is ventilation. Using most common chargers on the market, or any charging system with an overcharge feature, your vehicle’s battery will begin emitting a variety of gases.

Among these gases are oxygen, hydrogen sulfide and hydrogen. It is the latter two in particular that can be dangerous if allowed to build up in quantity, and are responsible for the vast majority of urban legends and legitimate tales of woe resulting from the charging a battery inside.

Luckily, you can mitigate virtually all the danger simply by ensuring that your battery has plenty of ventilation, either by opening a window nearby or just placing it in a drafty room but has plenty of air moving in it.

Failing to follow this safety protocol can result in serious problems and place you, your family members, and pets in danger although this is still highly unlikely.

Hydrogen sulfide is typically produced when a battery is being overcharged, and has a rotten, eggy smell. If allowed to accumulate in sufficient quantities, it can be harmful to people.

Hydrogen sulfide is heavier than air, and sinks toward the floor, making it especially dangerous for pets and children.

Again, the smell is highly noticeable, and if you smell more than the faintest whiff when charging your battery you should discontinue charging and improve ventilation in the room immediately.

Hydrogen is altogether a different problem, though it is a component of hydrogen sulfide gas. Hydrogen is extremely explosive, far lighter than air, odorless and tasteless.

Lucky for us, even when overcharging a battery hydrogen is produced only in tiny quantities, and is so mobile in the air it will take any advantage to escape a room that is not perfectly sealed, and do so quickly.

That being said, it is possible for off-gassing hydrogen to ignite above a charging battery once it reaches as a little as 4% concentration in the air.

Generally, unless you are charging many batteries at once in a tightly sealed room, you will not have to worry about hydrogen gas building up and then exploding your home, but you must remain cautious.

Also keep in mind that both of these gases can negatively affect the furnishings and finishes in your home, particularly fabrics and metals, by discoloring or corroding them.

Place Battery Away from Heat and Open Flame

Never, ever charge your battery near a source of intense heat or open flame. The gasses being released may ignite near open flame and the battery itself will already be warming up due to the charging process, especially if it is charged incorrectly or deliberately overcharged.

Don’t place it near any baseboard, floor or oil heater, fireplace, pilot light, oven, gas burner, stove or near any other heat source.

Keep Kids and Pets Away

If you have little ones and pets, it is imperative that you keep them away from both the battery and the charger while the charging operation is underway.

A battery that is malfunctioning or being overcharged may bubble and fizzle with dangerous chemicals. It could grow painfully hot. The charger’s cables are energized in operation, and any inquisitive pets that try to chew through them will be in for a nasty surprise.

Also anything that knocks over the battery or the charger may rupture them resulting in damage and injury. If you cannot trust your pets or your kids to leave your setup alone you must secure the room where the charging is taking place.

Beware a Short Circuit

You must use the greatest possible care to prevent any metallic object, like a tool, from contacting the terminals of your battery.

This will cause sparks and could potentially weld the tool to the terminals, causing it to become extremely hot and, potentially, slag the terminals themselves.

This can cause a chain reaction if they melt or sag through the casing of the battery for contacting the acids and chemicals within, likely causing an explosion.

Keep the immediate area around your charging operation completely free of all extraneous tools, silverware, wire or anything else that could cause a short circuit.

Use the Right Charger and Right Settings for Your Battery

It is important that you use the right charger with the right settings for your battery. Generally, you do not want to use any charger or charger setting that will automatically overcharge or automatic “desulfate” your battery.

Both processes overheat and dangerously overcharge the battery, not only resulting in a shortened life, but also potentially releasing dangerous quantities of the gases described above.

The best way to charge a battery indoors is with the minimum amount of amperage over the longest possible time. Consult your batteries at specifications and your charger’s manual for details. If you are rushed for time, don’t charge your battery inside.

Don’t Charge Overnight

Or, rather don’t start your recharging operation and then go to sleep. If your charger malfunctions, your battery fails or you just accidentally set the charger incorrect will not be awake to arrest the problem.

This could result in dangerous build-ups of gases, fires or potentially even an explosion. Don’t risk it!

Time the recharging operation to coincide with hours when you are awake, alert and able to react quickly to any mishap.

If you are forced to charge the battery overnight, or leave it behind while it is charging, double check the battery, your charger and the charger settings, and never do this unless the charger is equipped with a “float” or “maintenance” mode That will stop sending charge once the battery has reached its factory prescribed capacity.

Conclusion

Charging a car battery indoors is safe so long as some simple procedures are followed and you use the right equipment for the job.

The main concern when charging indoors is properly ventilating the room that the charging is taking place in, keeping the battery away from any open flame or source of heat and keeping inquisitive pets and explorative children away from the battery and the charge.

So long as this is done, you will have little to worry about when charging your vehicle’s battery indoors.