How to Use a Battery Tester on Your Vehicle

How to Use a Battery Tester on Your Vehicle

No car battery lasts forever. In fact, a typical battery found under the hood of a combustion engine vehicle is designed to carry an ever-decreasing amount of electric charge for three to five years before its power is ‘discharged.’ Automotive batteries are being tasked to power more components than ever thanks to modern technology like GPS navigation, LCD screens, DVD players and connections to Bluetooth devices. So, before you hit the road for holiday travels to grandma’s house, it is a good idea to perform a car battery test.

A car battery tester is an automotive diagnostic tool engineered to test the remaining capacity of a battery’s overall charge (an automotive battery tester does not test for voltage; that is a different electronic piece of equipment discussed below). Keep in mind when car battery testing that you are basically measuring the specific battery’s direct current. This diagnostic reading is a short comprehensive test of your battery health: capacity (available energy storage) and self-discharge (cell integrity). 

To test a car battery, you or an automotive technician will apply a load to the battery unit and monitor the response to measure how much power remains in a used battery. Load testing a battery is a quick DIY task. Clean the battery terminals and connect the load tester’s clamps to the appropriate positive and negative battery terminals. Follow the directions for the exact load tester you are using and wait for the test results. The battery should not fall below 9.6 volts, but results could vary based on battery temperature.

The instantaneous hand-held battery tester is a great basic option with which to equip your toolbox and use on any vehicle battery (hot or cold), including a small boat, ATV, RV or riding lawn mower. For more powerful heavy-duty, industrial fleet or commercial farm equipment batteries, purchase a hand-held heavy-duty battery load tester. You could also go with a digital voltmeter for continuous monitoring on a wide range of applications from 8 to 16 volts. This backlit voltmeter gauge provides at-a-glance monitoring of a battery while remaining vibration, temperature and moisture resistant.

The SOLAR 100 Amp Analog Fixed Load Battery Tester, which features an easy-to-read, color-coded meter with a graduated scale for assessing battery condition, is great for keeping it simple. NAPAOnline also sells a large selection of battery testers for automotive service shops from popular brands like SOLAR, Carlyle and DHC. For instance, shop owners can link this DHC battery tester to a computer system and text results to a customer or print off a report directly. 

Should You Use a Multimeter to Test a Battery?

Technological advances in battery testing equipment have reduced the size of these devices, while expanding the information available in the palm of your hand. Sophisticated battery testers can measure voltage, resistance, temperature and charge. Check out the portable SOLAR 40-1200 CCA 12 Volt Digital Battery & System Tester with a 4.5 to 16V operating range. This one device can test conventional flooded acid, AGM flat plate, AGM spiral wound gel cell, start-stop AGM and start-stop enhanced flooded batteries.

When a battery tester expands the available readings to include not just the electrical current, but the entire system’s running voltage and internal resistance (ability to deliver a current), it is often called a multimeter. Essentially, a battery tester tells you what a used battery can do, while a multimeter gives you the real-time effectiveness of a battery’s operation in your vehicle. Our NAPA experts recommend the TrueBlue 31 Auto-Ranging Digital Multimeter, which has a 1,000-volt auto-range plus features a no-contact voltage detector and integrated led flashlight or the comprehensive Bosch MMD 540H Hybrid Vehicle Multimeter kit for hybrid vehicles.

To measure an electric system’s condition, most testers need a connection to the circuit through wires. Simply connect the positive end of the multimeter to the battery’s positive terminal. Then connect the negative end to the negative terminal. Your comprehensive multimeter should quickly display a conclusive assessment of your battery’s capacity, as well as a reading on the alternator output and starting system capacity.

How to Test a Car Battery

If you plan to use a simple vehicle battery tester, then allow your car battery to sit idle for at least an hour before connecting. If the battery tester reading registers less than 12 volts, it is possibly time to replace your battery. While your vehicle is running, your battery should register between 13.7 and 14.7 volts for optimal performance. If your used car battery gives off a reading of 12.4 volts or less while running, your vehicle battery isn’t being sent enough power or it is nearing the end of its lifecycle. If your automotive battery reaches 11.9 volts, the battery is considered fully discharged.

In addition to gauging the battery’s strength while your vehicle is running, you’ll want to test your battery’s performance when carrying a large load (such as starting your car). Called the cranking method, this test requires starting the vehicle and pushing the gas (while in park) to reach 2,500 RPMs for five seconds. It often helps to have one person start the car, while another person reads the data from the voltmeter or multimeter. 

Set the connected voltmeter above 10 volts. The number should begin to drop as the vehicle runs. If the gauge doesn’t fall below 9.6 volts, you have sufficient cranking power. If it falls below 9.6 volts, then you need to replace the car battery. Next, the meter reading should start rising as the alternator recharges the battery. Within 20 seconds you’ll have both the load test readout (the low score) and the normal running readout (the high score). Together, both scores serve as indicators of automotive battery health.

NAPAOnline is your go-to shop for car batteries, battery parts and battery testing tools. Don’t forget to stock up on test leads for performing a battery test or stay even more prepared with this 10-piece Multi-Meter Test Lead Kit by NAPA, which provides large crocodile clips, flexible silicon pins and 64-inch-long interconnect test leads. For professional assistance checking your car battery health or getting it replaced, schedule an appointment with a local NAPA AutoCare Center near you today.