Updated August 2022
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Buying guide for best battery load testers

Vehicle battery health is often overlooked, yet a quick and easy check a couple of times a year with a quality battery load tester can identify problems before your battery lets you down (and you just know that could happen at the most inconvenient time and place).

The challenge comes in finding the right model. There is enormous choice in terms of price, accuracy, and available features.

Our picks provide a cross-section of the best on the market and offer effective solutions for the vast majority of people. Our battery load tester shopping guide gives detailed information and answers a range of buyer’s questions.

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Some battery load testers aren’t just for vehicles. Devices are also available to check alkaline, lithium ion and nickel types used in digital cameras, flashlights, etc.

Types of battery load testers

While most people think of a battery load tester as a device for checking automotive batteries, there are also those designed to test household batteries found in electronic gadgets like cameras, toys, and flashlights. In this guide, we’re concentrating on vehicle battery load testers.

What does a battery load tester actually test?

The basic job of a load tester is to check volts and amps, though some models can do much more than that. Volts can be looked at as the amount of energy available within the battery. A 12-volt automotive battery should actually read 12.6 volts when fully charged and the engine is turned off, and somewhere between 13.7V and 14.7V when the engine is running. For a 24V heavy-duty truck battery, simply double those figures.

When the energy starts to flow, it’s measured in amperes, commonly called amps. All vehicle batteries have a cold cranking amps (CCA) rating. This is the number of amps a battery needs to maintain a voltage of 7.2V for 30 seconds at 0°F. In practical terms, it’s the number of amps required to start your vehicle. For a family sedan, that’s probably around 400 amps. For a big rig, that could be 1,000 amps. Each battery has the CCA marked on it.

Ideally, a load test should be performed at 70°F or warmer. The testing device measures the voltage for 15 seconds at 50% of the battery’s stated CCA. If it produces a consistent 9.6 volts, it passes. Less than that, it fails.

In practice, many battery load testers will provide a good deal more information. Depending on which model you buy, you can get the percentage charge, voltage, rated and actual CCA, internal resistance, and a battery health reading (an estimate of the life remaining as a percentage).

Some testers take the reading much quicker than the standard 15 seconds. Many are capable of checking your alternator as well. An alternator not only keeps your battery’s charge topped off, it also supplies power to your vehicle’s electrical devices while the engine is running, so it’s a vital part of the system.

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Be careful when handling lead acid batteries, particularly the unsealed type. They give off hydrogen, which is flammable, and contain sulfuric acid, which can give you a nasty burn if it comes in contact with your skin.

Choosing a battery load tester

  • The first thing to look for is the voltage covered. A 12V tester is fine for many people, but some will measure both 6V and 12V, others measure 12V and 24V.

  • You also need to know if it is capable of measuring your battery’s CCA. Many read to 1,000 amps. Some go up to 2,000.

  • There are numerous battery technologies — flooded (regular lead acid) batteries, gel, AGM flat, and AGM spiral — and you’ll need to know the type that you have, as some basic battery load testers won’t work with all types.

  • Most low-cost battery testers have an analog needle that indicates results against a printed label. Digital displays give more precise information and are easier to read, especially in low light conditions.

  • Testers have wire leads that connect it to the battery with clamps. If the leads are short, it can be difficult to move the tester to a position that’s easy to read. Look for models with leads of at least several feet.

  • Leads with smooth-edged clamps may fall off the battery during testing. Serrated clamps tend to provide better grip.

  • A few models offer an optional printer so you can keep a paper record of results. There are also those with USB and/or Bluetooth capabilities, allowing you to send data to your computer or output it to a compatible printer.

Battery load tester prices

Very basic load testers can be found for around $10. Those that can actually measure battery condition start at around $45 and run to about $100, largely depending on the variety of battery sizes they can check.

Battery load testers with basic analog needle indicators cost as little as $25 for a 12V-only model. Those with digital readouts are about $5 more, though models this cheap may not always be accurate. We suggest investing a little more, with reliable devices available for around $40.

Dual voltage 6V/12V models run from $45 upwards. 12V/24V testers are considerably more expensive, costing from $90 to $130. Models designed for professional use can run into the thousands of dollars.

Vehicle battery safety tips

  • When working with vehicle batteries, wear safety goggles and latex gloves to protect yourself from acid splashes.

  • When you disconnect a battery, take off the negative first, denoted by a negative symbol (–) and a black cable, then the positive, denoted by a positive symbol (+) and a red cable. When re-connecting, it’s positive first, then negative.

  • Avoid working near sparks and open flames. Batteries give off hydrogen gas, which is highly flammable, and in a confined area, it could cause an explosion.

  • If the tester indicates that your battery needs to be recharged and you’re using a basic trickle charger (also called a battery maintainer), don’t leave it on too long. Overcharging can ruin performance and could cause sealed batteries to distort or crack open. Smart chargers are a much safer option.

Other products we considered

Although not strictly speaking a load tester, the Innova 3721 Battery and Charging System Monitor is a low-cost yet valuable device that could forewarn you of potential battery problems. It works conveniently from inside your vehicle, in the dashboard power outlet/cigarette lighter socket. 

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A good load tester doesn’t just tell you about your battery, it can measure the condition of your alternator, too.

Battery load tester FAQ

Q: Does my battery need to be fully charged before testing?

A: It depends on what aspect of the battery or charging system you’re testing, but it’s a good idea where practical in order to get the most accurate reading possible. However, some experts recommend not testing immediately after charging because batteries can hold what’s called a ‘surface charge’ that will give a false reading. They suggest waiting for at least a couple of hours after charging before testing. A healthy battery won’t lose noticeable charge during that time.

Q: Should the vehicle engine be running during testing?

A: If you’re testing for battery charge, the engine should be off. If you’re testing the alternator output, the engine should be running.

Q: Should I remove the battery from the vehicle for testing?

A: You can, but you don’t need to. Be aware that if you do, some dashboard functions such as a clock or audio system anti-theft feature that require a constant charge will be disabled and you’ll need to reset them after re-installing the battery.

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