Getting a new battery for your car can be a great relief, knowing that you will not be stranded again with a dead battery.
There is a danger though of not knowing how to and whether to charge your new battery which can affect the overall performance and life of your battery.
In this post, I will go over:
- Whether you need to charge your new car battery before use
- How to charge your battery safely so that it lasts
- How long a battery lasts if not used
Do New Car Batteries Come Charged?
Most new car batteries come already charged (precharged). All that is left for you to do is to install it in the car and use it right away.
However, it is always a good idea though to confirm if your battery is precharged with the Authorised battery seller first or to consult the battery user guide.
If your battery needs charging, you can use the charging methods described below.
Should You Charge a New Car Battery Before Use?
Not necessarily if the battery manufacturer or dealer has indicated in the battery documentation that it is already charged and can be used right away.
That said, you can measure the battery’s Open Circuit Voltage of the battery with a good quality digital multimeter.
To get a more accurate meter reading, always first, disconnect the battery from any wiring and leave it to stand still for about 10 minutes if it has been charging before taking the meter reading.
A fully charged AGM 12V battery measures about 12.6 -12.8 VDC.
If your multimeter has a reading below 12.4V then you need to charge your new car battery.
If you are unsure whether your new battery comes precharged and is ready for immediate use, you can play safe and charge the battery using an external charger first before use.
Make sure it is set to charge your battery type – AGM or otherwise and whenever possible use a low amperage 10 – 20A voltage regulated charger.
In the next section, we look at the options available to you if you need to charge your car’s battery for the first time.
How to Charge a New Battery for the First Time
If you are charging a new car battery for the first time, if it is precharged (most car batteries are), you can install it in the car.
Make sure to follow the battery manufacturer installation instructions.
How long to charge a new car battery for the first time
After installing, drive for 15 or so minutes so that the car’s alternator tops up and maintains the battery charge.
Alternatively, you can follow the steps describe above to charge your car’s battery using an external charger.
How to Safely Charge your Car Battery For a Long Life?
1. Use a Voltage-regulated charger set to charge the correct battery type
Use a voltage-regulated charger for your batteries.
Check that it is set to charge your battery type Flooded, GEL, or AGM – if your new car battery is AGM, make sure that the AGM setting is activated.
For an AGM battery, your maximum voltage should be set to 14.5 VDC to prevent overcharging the battery.
Use a low-amp (less than 20-amp) charger
If you are using an external charger, go for a 10 – 20 Amp charger.
Keep in mind that low-amp chargers are better for battery life (less temperature buildup in the battery) even though they take a longer time to charge the battery.
2. Monitor the battery temperature during charging
Besides making sure that your voltage and current settings are set right, you should also monitor the temperature of the battery during the charging process.
It should be warm to the touch. Should the battery become hot, you need to discontinue charging to avoid the risk of explosion.
You may want to check out our guide on How many amps should you charge an AGM battery at?
How long should I let my car run after installing a new battery?
Should You Run your Car Engine After Installing New Battery?
While most if not all new car batteries are likely shipped as precharged, it is a good idea to start your car and run the engine after installing the battery if only to test that the connections are firm and your car starts without hesitation.
Though not explicitly required, run your car’s engine for 10 or so minutes at least so that your car’s battery charge is maintained.
If the cranking of your car is slow, then your battery’s charge level is low.
In this case, you can charge with an external charger or run the car for 15 or so minutes to charge it fully.
Continue to monitor your battery over a couple of days checking if the car starts instantly.
If you have a repeat of slow cranking, you should consider returning your battery and getting a new battery as a replacement.
1. Why your New battery May Not be Holding Charge
One problem you may experience with your new battery can be that it is draining too fast even when it is fully charged.
If this is the case, possible causes of your battery not holding charge are:
- You have parasitic loads that are draining it. Check out this article on What can drain a car battery with the engine off?
- Bad battery. You may take it for a battery test or monitor its voltage out of the car over several days after a full charge.
If the battery voltage still drops considerably, then you probably have a bad battery.
Check out this article on How to tell if you have a bad alternator or a bad car battery
2. How Long Does a New Battery Last if Not Used?
A fully charged new battery put into storage and not used can hold its charge and be able to start the car for about 6 – 8 months depending on the quality of battery manufacture.
For it to last and hold its charge for this long, make sure that it is stored in a cool, dry location and that it is fully charged.
If the battery is installed in a car that is not used, a fully charged battery can last for about 1- 2 weeks after which it may fail to start the car depending on the combined current drain by the car’s electronics – alarm, GPS, onboard computers and others.
For the battery to last longer, consider:
- installing a maintenance charger connected to the car battery to keep it topped up always
- disconnecting the car battery if it is an older car without electronics whose memory needs to be backed up.
While most new car batteries are likely precharged, it is always best to consult the battery manufacturer or check the battery installation documentation.
If it is already charged then installing it in the car and running the engine for 10 or so minutes can help maintain the battery charge.
An external battery charger is good option to charge a new battery that needs to be charged. Make sure though that it is set to charge your battery type – AGM, GEL, Flooded and preferably set it to charge at a low amperage (less than 20A).
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