How long does it take to charge a car battery?

It can take between an hour and a day to charge your car battery depending on the type of battery you have, and the amperage of the charger used.

The different types of charger

You may have noticed there are all sorts of battery chargers on the market and understanding their different uses is key to picking the right one for your situation.

Generally, the time taken to charge a battery from flat to full is determined by the amperage of the charger used.

Linear battery chargers are the simplest kind of charger and will allow you to charge a battery via a wall socket without any bells and whistles, but often operate at low amperage.

Generally, the time taken to charge a battery from flat to full is determined by the amperage.

The cheapest available Repco-branded battery charger, for example, runs at 2.7amp which will easily take up to 12 hours to charge a run-of-the mill 12-volt lead-acid battery (as is found in most cars) to full.

Linear battery chargers simply continuously charge a battery, and do not have controllers that stop charging the battery when it is at capacity. This can cause damage to the battery’s lifespan, or even cause the battery to explode or fail in certain conditions.

Multi-stage battery chargers are more expensive (ranging from $90 to $1100) but recharge the battery in bursts. This is healthier for battery cells and resists long-term damage that can be done by simply charging them continuously.

Multi-stage (also known as smart or intelligent chargers) are also available at much higher amperage, up to 50A which will allow you to charge a standard car battery in less than an hour.

NRMA tells us that while batteries charge faster at higher amperage, it is better in the long-term to charge at lower amperage as rapid charging can negatively impact battery life.

Pricier chargers will also have gauges or indicators to let you check the voltage of the battery.

Trickle chargers are the last kind of charger and operate at low amperages (between 0.8A – 4A). These are not meant for charging a battery when it goes flat but are meant to prevent the problem in the first place by being connected to the battery in times when the vehicle is not in use.

Trickle chargers operate at low amperages.

If you have a more advanced battery such as an Enhanced Flooded Battery (EFB) or an Absorbent Glass Mat (AGM) battery (the kind often used to support cars with stop-start systems), NRMA tells us this is a good thing as these types of batteries can be charged the same way, actually accept charge faster than their standard lead-acid counterparts, and are designed to operate properly at lower voltages.

What if you jump start your car?

We don’t recommend using jumper cables for starting most modern cars where you can avoid it, as there is a risk that modern electrical systems can be damaged in the process.

If you were stuck in a pinch and had little choice though, how long would you have to drive or idle the car to charge the battery back up again, so you can safely turn the vehicle off and expect it to start again later?

NRMA’s advice for a standard battery is “around 30 minutes.” This is because a car’s alternator operates at between 50 and 100A, thus charges a battery relatively quickly.

We don’t recommend using jumper cables for starting most modern cars.

Roadside support services like NRMA, RACQ, or RACV, or even a manufacturer roadside support service can safely jump start modern cars without risk to electrical systems through use of a spike protector, with regulated voltage via an Anderson Plug.

These tools prevent damage to the battery and negate the chances of a spark occurring which can cause a battery to fail.

If in doubt when it comes to what kind of battery you have or need to jump-start your vehicle, it is best to contact one of these services.

Have you had trouble charging a car battery before? Share your story in the comments below.