How long does it take to Charge a car Battery with a 12 volt charger?

Stuart Wellbert
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Batteries are an essential part of any vehicle. While gasoline is an extremely efficient fuel source, it doesn’t have a long shelf life. It can also be easily spilled or leaked if it’s not handled properly. As long as you keep the gas tank full and well-sealed, you won’t have to worry about a leak. On the other hand, batteries are small, easy to store, and don’t require a special device to get them to work.

A battery is an electrical energy storage device. It is composed of chemical elements that create electricity. Chemical elements move about in a small container and produce a flow of electrons. This flow of electrons powers just about everything electrical in your vehicle, including the lights and the ignition system.

Batteries also come in different types. The main difference between most of them is how large they are and how long they can hold a charge. The most common batteries found in vehicles are 12 volt.

In each cell of the battery, a chemical reaction happens within the container. In order to start a chemical reaction, electrons must be flowing through the cell. When electrons flow in a circuit and reach the end of the line, they must have a way to get back to the beginning of the circuit.

How long to Charge a car Battery at 40 amps

Well, let's break it down a bit to get the best answer possible. It's actually easier to think in terms of what it's equal to, which is like considering the speed of movement in relationship to the amount of time it takes to reach a given destination.

So, how many amp hours is your car battery?

Well, battery capacities are measured in amp hours. For the sake of our example, let's say your battery is 60 amp hours (the average battery for a vehicle). If your battery were to be charged at 40 amps, how long would it take? Well, that's 6 amp hours per hour, so 6×60=360.

Divide the amp hours of your battery by the amps applied and you've got your answer. 360/40=9 hours.

(i.e. More math: Amp hours = Amps x Hours / 1000)

That's actually really fast. In 9 hours, your car will be fully charged with a 120-volt charger. To put it in perspective, it takes the same amount of time to charge as it takes to watch 2 movies on Netflix.

If you use a 240-volt 50 amp charger, you're charging speed doubles. 84 amp hours will be transferred in 4 hours (84/50= 2.4).

How long to Charge a car Battery at 2 amps

A good indicator of the time to charge a car battery with a 12 volt charger is its amp rating. For instance, a 2 amp charger would take twice as long to charge the battery.

It is not uncommon for car battery chargers to have four or even six amp capacities. Even though the charging capacity is high, these battery chargers have 12V ratings, which sets a standard for how long the battery should be charged.

As a general time frame for charging your car battery with a 12 volt charger, consider each amp equal to roughly 20% of the capacity. If your battery is below a 60 amp capacity, then a 6 amp battery charger would be appropriate. If your battery is below a 100 amp capacity, then a 10 amp battery charger would be appropriate.

If you need to know how long a battery with a 12v rating will take to charge, estimate 20% of the battery capacity and then add that time to the overall recovery time set by the battery charger.

If you’re using one of the best battery chargers on the market with high-end charging capabilities for larger vehicles, then charging times could take well into the night or longer.

It takes a little finagling to figure out the best charging times for a charger based on the battery size. There is a rule of thumb that is usually applied but it can be deceptive. The rule is that the larger the battery, the longer it should take to charge. This sounds like a reliable rule but the reality is that while it’s a little bit true, there are plenty of variables that influence the actual charging time.

Some of the things that influence charging times is whether alternators are on or off and how much power is running through the battery, whether the battery is being charged on an automatic charger, and if you have any kind of electronic devices or accessories still connected to the battery.

To get an idea of your particular circumstances, check out some of the user reviews on your battery charger. These reviews will give you the real scoop on what other people have experienced with their chargers.

Towards the end of the charge, the charging time of a battery increases. This trend was reported in a case study by Oxford University which states that in the maximum state of charge, the charging time was double that of the initial charging state.

How long to Charge a car Battery at 4 amps?

How long does it take to charge a car battery at 4 amperes? The charge time for an automotive battery is determined by the Amp Hour Capacity, or Amp Hour (Ah) rating, of the battery. The Amp Hour rating is a measurement of the electrical charge (Amps) that can be discharged (1Amp=1000mA=1C) from the battery in one hour, or the time it takes to discharge 1 Amp for every 1000 mAh (1000 mAh=1 Amp Hour).

On the battery of your car, you'll usually find a series of 3 digits like the following:

The first digit is the number of 1000 mAh, the second digit is the number of 1000 mAh and the third digit is the number of 1000 mAh.

For example, a battery reporting 1218, has 12 1000 mAh, and 8 1000 mAh.

If your car battery reports 1000 mAh(1750), it will charge at least 17.5 times faster than a 2000 mAh battery.

The larger the Amp Hour rating of the battery, the longer it will take to charge. A 40 Ah battery should take twice as long as an 80 Ah battery to produce 1 Amp, or 1000 mAh, of electricity. If you were to charge a battery that has a 40 Ah Ah rating using an 80 Amp 12 Volt battery charger, it will take 1.25 hours to charge the battery fully.

How long does it take to Charge a car Battery with a Trickle Charger

A trickle charger or smart charger is a battery charger that that charges your battery at a slow, controlled rate.

An absorption battery charger, on the other hand, starts charging the battery in bulk (called the absorption phase) and then switches to float mode. It's far easier to use an appropriate charger for your batteries, as opposed to figuring out the charging times using math and your current charger.

Once you plug in the battery charger, the display will indicate how much it is charging based on the battery volts. Usually, this will be around 4 amps, but it can be as high as 15 amps for some chargers. Next, you'll want to figure out how much current is flowing into the battery.

To figure out the current, you'll need to know how long the charger has been charging. If it's been for 10 hours, the 10 hours are your answer. Multiply the two together and you'll know what the current is.

Next, you'll need to know how much your charger will charge your battery in 4 hours. If your charger gives you 4 amps, and you know it will charge your battery in 4 hours, you'll need to multiply the two together to find out how many amp hours your battery will take.


How Long Does it Take to Charge a Car Battery?

The following drivers were tested for electric charging times:

  • 100ah 12 volt Lead-Acid Battery
  • 245ah 12 volt Pure Lead Battery (new)
  • 245ah 12 volt Pure Lead Battery (old)
  • 79ah AGM (Absorbed Glass Mat) 12 volt Lead-Acid Battery

{1}. 5Ah 12 volt Lithium Ion Battery
{2}. 5Ah 12 volt Lithium Iron Phosphate Battery

Solar Panel Charging Times – 100%

Charging Time (hours) Volts Perah Battery* Watts Used ElectriCord Solar Panel AGM Lead-Acid (AgM) Lead-Acid (Pb) Battery (Pb) Battery (Pb) 5 16.5 36.5 60 89.5 119.5 12 33 61.5 93.5 149.5 190.5 24 52 91 142 229 265 36 72 122.5 182.5 298.5 360.5 48 92.5 173 230.5 363 435

Volts Perah Battery – The voltage of the battery when completely charged and discharged is calculated by dividing the Ah rating (ie. 240 Ah) of the battery by the number of Volts used by the battery system in one hour (ie. 12 Volts). This figure is an approximation as the actual voltage will vary from one battery to the next.