There are lots of factors that can cause a car battery to fail, but one of the most common problems is that the battery has simply gone flat. This can happen if you’ve accidentally left your lights on overnight, for example, but it can also be down to a fault with the car, excessive short journeys or even extreme weather conditions.
Fortunately, car batteries are rechargeable, and in many cases that’s something you can do yourself without having to take your car into your local garage. But if you’re having difficulty getting it done or you don’t have the time, Mr Clutch Autocentres can charge your battery up for you, as well as completing a battery health check to give you peace of mind.
How to charge your car battery
If you’re going to charge your car battery yourself, you need to know the correct methods. Although we’ve become accustomed to electricity being involved in all aspects of life, it’s important not to underestimate the potential risks of fiddling with batteries without knowing what you’re doing. You could get a nasty shock, and it might even damage your vehicle!
Below are the two most common methods for charging car batteries.
Does a car idling charge the battery?
Many people are aware that you can charge your car battery simply by driving or idling the car, but did you know that there’s a limit to the effectiveness of this method? Simply put, a component called an alternator converts the rotational power of the car’s engine into electrical energy, which charges the battery.
However, the amount of revolutions (revs) per minute matters here. While idling, you aren’t typically using enough revs per minute (rpm) to generate enough power to charge the battery in a meaningful way. Yes, your battery will be charging, but it will take a very long time to do it if you stay idling.
Driving, therefore, is a better option – but it’s still not ideal. Once the car has started, the alternator will provide enough power to give you the basics you need while driving, but it might not be enough to support extra electrical demand such as charging your phone or listening to the radio. And if your battery was low to start with, driving might not charge your car enough to
prevent difficulties in starting it the next time you turn the ignition.
Another thing to watch out for is the battery indicator light on your dashboard. This usually comes on for a second or two every time you start the car, but if the light stays on, that means there’s a problem somewhere in your battery or alternator. You should be alright to drive, but it’s important to get to a garage as soon as you can to have the issue checked out, because there’s a big risk that the engine might not start again the next time you come to use it.
Assuming there are no problems with the battery and it wasn’t very low to begin with, charging your car’s battery while idling and driving can work. The higher the revs the better, but only to a point – revving the engine only increases the charging speed to a small extent, and it can cause problems elsewhere in the car. Driving for a reasonable amount of time at high speeds, such as on the motorway, will usually charge your battery better than short, stop-start driving like a city commute. In fact, this kind of driving can actually drain the battery, which is part of the reason why flat batteries aren’t solely a winter issue.
If your battery was low to begin with, however, it’s better to use a plug-in car battery charger to get the job done.
How to disconnect a car battery for charging
Charging a car battery is a slightly different task to charging a few AA batteries, but it’s still something most of us can do at home without issue. First, you need to make sure you have a charger that’s right for your car’s battery. Conventional chargers suit the majority of batteries, but if you have an AGM or EFB battery – in other words, if your vehicle has start/stop technology – you’ll need a ‘smart’ charger instead. Once you’ve got the right equipment, you can get started.
Locate the battery and check the contacts
If you’re not sure where your car battery is located, it should be detailed in the vehicle handbook. Most car batteries are under the bonnet and easy to spot, but some cars have them under the boot compartment instead.Once you’ve found it, it’s important to check the lead terminals on the top of the battery and the clamps that connect to them. If they’re corroded or dirty, make sure to clean them and check that they’re completely dry before charging the battery.
Disconnect the battery
It is possible to charge your car’s battery while it’s still connected to the car, but it’s much safer to disconnect it first. There’s a specific method to this to keep yourself from getting a shock, so don’t rush this part. You’ll need to disconnect the terminals from the battery by undoing the clamps in the following order:
Negative (typically black) first
Positive (usually red) secondCharge the battery.
Never leave the charger on top of the battery while it’s in use. In fact, it’s best to keep the charger as far away from the battery as the cables will allow. The charger will have familiar positive and negative terminals. Connect the charger’s positive terminal to the battery’s positive, and negative to negative. Then turn on the charger.
Some chargers turn off automatically when the battery is at 100%, but others don’t. You should be able to find out either way from the manual for your charger, which may also include information on how long it will take. A little run-over shouldn’t be a big problem, but it’s best to turn off the charger as soon as possible after reaching 100% to keep your battery in good health.
Put everything back again
Once the battery is charged, unplug the charger and detach the terminals from the battery in the following order:
Negative first
Positive second
Then you can reconnect the battery to your car’s terminals in this order:
Positive first
Negative second
You may need to reset your radio, the dashboard clock and other electronic settings such as seat positions after reconnecting the battery. But from a driving perspective, you should be ready to go!
How long does it take to charge a car battery?
Car batteries need a lot of electricity to power your vehicle, so unfortunately it can take a bit of time to charge them up. The exact figure varies depending on the charger you’re using, the type of battery you have and how low the charge was to begin with, but it can take as much as a day or longer to charge a battery fully. You might wish it was quicker, but this slow charging actually helps to protect the battery from overheating damage.
Charging your battery by driving is affected by too many variables to give a meaningful estimate, but you can expect it to take a lot longer than using a charger would.
If your battery is losing charge quicker than you expected, your dashboard is showing the battery indicator or you’re at all unsure of what to do when it comes to your car battery, don’t hesitate to take your car into the garage for a battery check or replacement battery if needed.
Mechanics can use specialist diagnostic tools to help get to the bottom of what’s causing the problem and advise you on how the issue can be dealt with safely and cost-effectively. test