To test each car battery, we unpackaged it and attached it to a 12.0-volt wet cell battery. We started the battery charger according to the instructions and measured the voltage using a multimeter.
By considering a battery charger’s voltage and amp hours, you can determine the approximate charging speed. Batteries that charge a car faster received a higher rating in this category.
Most car batteries are 12.0 volts. A higher voltage will charge a battery more quickly, but too many volts can damage your battery. A few volts above a battery’s rating are acceptable and even desirable, but a car battery charger must produce at least 12.0 V to charge a 12.0-V battery. Maintaining a consistent voltage is also important for charging speed and battery protection.
Not all car battery chargers will work with every type of battery. While most cars use a wet cell battery, some may use an absorbed glass mat (AGM), gel, or lithium-ion battery. Chargers compatible with the most types of batteries scored best in this category.
Additionally, some car battery chargers have features such as overcharge protection and trickle charging options. Such features also contribute to a battery’s versatility rating.
Ease of Use
An easy-to-use automotive battery charger has long clamp cables and durable alligator clamps. Battery chargers are also easy to use if they have long outlet cords and straightforward interfaces and instructions.
We gave the highest ease of use ratings to battery chargers that could start charging with few button presses, came with strong alligator clips, and featured long cables.
Our value score is based on the relationship between a battery’s rating in all other categories compared to the price.
How We Score Car Battery Chargers
Every car battery charger we test is given a score between 1.0 and 5.0 stars in each category. Here’s what those star ratings mean in concrete terms:
- 5.0 Stars: A 5.0-star rating means a car battery charger is among the best in a category. It can charge any type of battery quickly, includes automatic battery detection features, or works automatically on any battery.
- 4.0 Stars: A 4.0-star rating means a car battery charger performs better-than-average in a category. It offers fast charge times and is powerful enough for diesel engine vehicles, can be used with most types of batteries, or can be set up with the push of a button.
- 3.0 Stars: A 3.0-star rating indicates what is average or typical for a car battery charger, based on our testing experience. It is powerful enough for most passenger vehicle batteries, can charge AGM and Lead-Acid batteries, or is easy to use with some setup.
- 2.0 Stars: A 2.0-star rating indicates the car battery charger performs poorer than average. It doesn’t deliver enough power for common batteries, can only be used for one type of battery, or is confusing to operate.
- 1.0 Star: A 1.0-star rating indicates that the car battery charger performs well below expectations in a category. It is utterly powerless, drains quickly, or cannot be safely operated by a layperson.
Why Trust Motor1.com
Each year, we test over 350 auto products on vehicles and in our testing lab. Our team of product testers thoroughly researches top products, unboxes and puts our hands on each component, and tests the items on real vehicles before making recommendations to readers.
We publish hundreds of product and service reviews to bring car enthusiasts detailed guides on automotive tools, detailing kits, car seats, pet products, and much more. For more information on our testing methodology and how we evaluate every product, check out our methodology page here.
*Data accurate at time of publication. Products subject to availability.