Are you facing issues with your car battery? Did it make that awful sound when you ignited it? It could be that nothing happened at all when you turned it on. Here’s how to check a car battery with a multimeter to get accurate reading.
Calculating a Car battery volts
Generally, car batteries are expected to have about 12.6 volts. However due to battery discharge, it’s necessary to check and determine the voltage a battery will settle at 12-24 hours after being removed from the charger. To get the accurate gauge of the health of your battery, test the car battery in the morning before starting the car.
A recently used and charged battery will certainly bring out a boosted reading other than the actual resting voltage. Therefore, to gain the correct reading allow the car to stay for about 12 hours without being used and then, carry out the testing using a multimer.
However, you can handily check a car battery with a multimeter yourself, locate the battery terminals and do the testing. But before that, you will have to locate the battery position. Generally, they are placed at a corner of the engine inlet. So you can easily find the battery when you open the hood.
In the same vein, recent cars come with a battery cover. So, carefully pull out the cover using the required tools. After successfully uncovering the battery, take precautions not to cause damage to either the battery or other parts.
How to check car battery with multimeter
The initial test using a multimeter will measure DC voltage, specified with solid and dashed lines above a letter V. Now, set the dial to 20, which will enable you to properly measure between 0-20 Volts.
Touch the red probe to the positive terminal, and the black probe to the negative terminal of the battery to be tested. You will determine the positive and negative terminals as it will be marked + and – respectively. A reading starting with a minus in front of it (-12.5 rather than 12.5) shows an error and you have to switch the probe to the correct side.
Moreover, the resting voltage shouldn’t be lower than 12.6V. Also if a battery reading is 12.2V, it means the battery is 50% charged and readings below 12V means its discharged.
A simple and working way to preserve a car battery life is to disconnect it from the car after use. This will fix the problem of the batter discharge even when the car is turned off. There are lots of features and components in the car that will keep on draining the battery even when the car is turned off. So to prevent unnecessary battery drain, simply unplug the cord connecting the battery head to the car.
Therefore, when you record less than 12.6 volts, fully charge and leave it over night before test.
How to test the alternator with a multimeter
The alternator is responsible for producing electricity in a car and also charge the battery. It is in charge of delivering power to the car’s electrical systems and also responsible for recharges a car battery.
When the engine is on, simply use a multimeter to test the car battery charging system. You can perform this by taking the same above process used to check car battery with a multimer. This measurement should be 13.8 to 14.4 volts at regular idle speed and if the battery is in order.
After the battery testing and it shows that the battery reading is below or above that range, it shows the battery is either under, or over charging. Here, you will need the service of a professional as this may cause critical damage to both the battery and the alternator.
Testing a car battery for dead cells
In most cases, some cells that make up the battery will go dead and not the battery itself. This can easily be noticed when attempting to ignite a car.
Some recent cars batteries are sealed and maintenance free type, however, some car batteries give you to access the individual cells.
Therefore, a hydrometer-style battery tester that measures the specific gravity of the battery acid is required to test each cell. You can determine if a battery cell is dead or not with the number of balls floating.
Finally, after going through the above guide you will be able to check car battery with multimeter and determine if it’s in proper condition. Also, be able to calculate battery volts, test for dead cells and be able to check car battery charging system. Thanks for reading.