Business photo created by peoplecreations – www.freepik.com

How to do a battery load test?

I do recommend doing a battery load test by yourself.  Sometimes you will be spending extra on purchasing a battery you don't need for the recommendation or faulty test in some auto parts stores and automotive repair shops.
What you need:

your battery
a multimeter
a battery load tester

To do the battery load test, first of all, I suggest that you remove the battery out of your vehicle. One of the reasons is to help you fully connect the clamp on the terminal of the battery. Next, you can test your battery in a safe place rather than your vehicle full of gas and stinks. Any acid from the battery might cause corrosion or even an explosion. Wearing safety glass and latex gloves are also recommended. You always want to be safe.

Before the battery test, make sure the terminals are clean. If the terminals need to be cleaned, just mix a small amount of baking soda to a bowl of warm water. Scrub the terminals with a toothbrush or a soft wire brush. 

Make sure your battery is fully charged. Use the multimeter to test the battery and ensure that the battery is or exceeds 12.4V. After that, you can conncet your battery load tester to the battery. Put the red clamp on the negative terminal and hook the black clamp to the positive post. The voltage read should be almost the same as what you got from the multimeter.

Push the test switch, not holding it longer than 10 seconds. When the needle stops moving, take the reading. If the battery reading is under 9.6V, it needs to be replaced. Chuck it. 

Check you spec of the battery. According to your CCA(cold-cranking amperage) of the battery, this will determine where it should fall on the graph of the load.