Can You Overcharge A Car Battery? If So, How?

by Phil Borges // in Car

Car batteries are an investment that should be taken care of. Luckily, overcharging a car battery is not all that common and usually only occurs from two issues.

The first is the voltage regulator in your alternator sending too high of electricity to charge the battery when it’s already full. This can occur if you’re driving on long trips for extended periods or during extreme heat conditions like Arizona summers, where they reach triple digits.

The second thing that would cause overcharge is the disconnection between your charger cord and vehicle. This would happen if your battery were to get disconnected from the charger cord, which would cause a current disconnect between the two.

Here are some ways you can tell if your car battery is being overcharged.

What can cause an overcharged car battery?

Defective Alternator

Alternators are like the heart of your car, keeping it running and charged. The voltage regulator is a crucial piece that regulates how much power an alternator makes available to your battery so you can run all day without worry.

If this component malfunctions or stops working at high-enough voltages, it could overcharge and damage your battery. It will then lead to some big problems in the long term.

Signs of a malfunction include increased connection, cold starting issues when you go outside in winter months, or if you notice any unusual odors coming from the underhood area while driving.

Charger Plugged Too Long: Can you overcharge a car battery with a trickle charger?

Ever wonder what happens when you leave a trickle charger plugged into your car battery for too long?

Trickle chargers are a useful tool for recharging your car battery. However, if left unattended, they can overcharge the battery and damage it. If you use one of these devices at home (which many people do), be sure to unplug them when not in use so that this doesn’t happen!

Cell phone chargers can be intelligent enough to detect when your cell phone is fully charged, but some trickle chargers are not.  If you’re planning on buying a charger or battery-trickle device, I would recommend making sure it has the ability to determine and stop supplying electricity. It should have a feature that determines if the battery is full. This way, there’s no risk of overcharging your gadget.

This Black and Decker battery charger (amazon link) automatically shuts off when the charge is complete but can also switch to a float mode that will monitor voltage. If your batteries drop below a certain threshold, it will turn back on and recharge them until they are fully charged again.

How do you know when a car battery is fully charged?

You know that your car battery is fully charged if you can read a voltage of 12.6 volts when the engine’s off and 13 to 14 while it’s running.

The best time to test this is after a drive or during an idle period, where there will be no acceleration demand on your alternator. If you get a lower reading than what is outlined here, then something could be going wrong in some way which may require taking care of soon!

Newer chargers will light up once the voltage exceeds a certain threshold and make sure that all of your electronics are powered through an efficient charge every time.

This is convenient because you don’t have to break out a multimeter. You can just let this charger tell you when it detects full charge on its own without any assistance from external devices like one would need in older models.

Can you overcharge a car battery?

No. If you’re noticing your battery dying more often (going dead completely) and/or sooner than it used to, there’s a chance that the car charging system is overcharging.

To check your car battery for overcharging, you will first need to obtain a multimeter if you currently don’t own one. Once you have the meter on hand, all that’s left is to power up and start your engine by idling it or turning it off and then back on again.

Next is to set your multimeter for DCV or direct current and choose a setting above 15 volts (I chose 20). You would then connect the red wire from the meter with the positive terminal on your battery. The black cable coming out of it will attach to any negative terminals around, but we recommend attaching it with whatever is easiest in front of you at this time.

From there, you would want to look at the readout from your multimeter. A reading anywhere from 13.6-14.8 volts means that it’s functioning properly. Still, if above 14 or so, this indicates a problem with either overcharging or discharging, meaning something is not working right somehow and needs repair for safety reasons!

How long should you charge a car battery?

The time it will take to charge a car battery depends heavily on the amperage that your charger has. A typical car battery, which can hold 48 amp-hours (or 12 volts), would take about 4 hours with 2 amps of charging power or 1 hour and 24 minutes if you have an 8 amps unit.

If you have a battery that is only holding 16 amp-hours, then it will take about twice as long at a minimum time of around eight hours. This means charging for an hour and 48 minutes with the two amps unit or three hours and 24 minutes with the four amps charger.

What happens if you leave a car battery charger on too long?

If you leave an overcharging car battery, it could damage the battery. The acid inside the lead-acid batteries will start to evaporate and render them useless. This is because they contain acids that react with metal plates to store electrical energy. Without these components, there’s no way that cars can charge up or power their electronics systems while running down the road!

Most manufacturers have developed smart features that allow these devices to tell if the battery has reached full capacity. Once they’ve detected this, then they will automatically turn off the power, preventing further damage from occurring.

Why do you need to charge a battery?

It’s important to take the time throughout periods of inactivity like winter, where you can’t start your vehicle, and ensure that it is charged. Otherwise, a battery might freeze over if left without charge for too long! To avoid this, be sure to use a charger/maintainer or periodically jump-start your car with another vehicle when possible.

New car batteries may also need to be charged before they are used because they’re not fully loaded for the first time. Most car batteries are made up of electrolyte which helps to power them and generate electrical currents that allow cars, trucks, motorcycles, tractors, etc. to function properly while in motion or idle.

Alternators work by converting engine power into electricity that is supplied to the battery. However, alternator charging systems are not designed for batteries that have lost most of their charge because they can be hard on the alternator. This means you should always make sure your car has enough juice before heading out!

Related Questions

Can you leave a car battery charger on overnight?

It’s not recommended to leave a battery charger overnight, but if you need to, then make sure the charger has an automatic shut-off feature so it doesn’t overflow your car battery!

How long after jumping a car should you let it run?

It would be best if you let your car run for about a minute or two after jumping to ensure that it’s fully charged. That way, when it needs a jump again, there’s enough charge in the battery for another attempt at starting up without needing help from an external source.

Does reviving the engine charge the battery?

No, but it does get the car moving for a short distance so that you can put it in neutral and coast or use the brake to stop.

Many people think that revving your engine will charge up their battery faster than keeping it idle, but this isn’t true since cars have alternators designed specifically for charging batteries (13.6-14.4 volts). If you put too much voltage into the battery, there is a risk of damaging or even exploding the cells inside, leading to significant and costly repairs.

What makes a battery explode?

A battery will typically only explode when the lead is crossed or if it’s been hit by an outside force. Batteries under normal operation and conditions don’t need to worry about exploding.

Under normal operation and conditions, you won’t have to worry about your battery exploding if they are not subjected to these events.

Can a car battery explode while driving?

This is not likely to happen as long as the battery cables are in good condition. Usually, a car battery will +leak out of its casing when it’s on the verge of exploding, and there isn’t usually enough power for that to occur while driving down the road.

Car batteries are not without risk, though. On the road or in a crash, they can and do explode on occasion! Be sure to take care of your battery by ensuring it’s never undercharged – because that could lead to an explosion one day too.


Overcharging can happen if you don’t know what you’re doing. Luckily for us, we have all of the knowledge and tools necessary to help make sure that doesn’t happen.

We hope this article helped you better understand how to avoid overcharging your car battery.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.