Car Battery Charger FAQ – Consumer Reports

There are two main types of chargers: trickle and maintainer. Basic trickle chargers slowly replenish the battery, but they need to be monitored and manually disconnected when the battery is topped off. A maintainer may be all most people need. True to their name, these budget-friendly chargers are meant to preserve the charge level, not resurrect a dead battery. Unlike trickle chargers, maintainers turn on and off as needed.

A battery maintainer will charge as needed, automatically. Advanced maintainers, often called “smart” chargers, typically have modes to address the needs of absorbed glass mat (AGM) batteries, ensuring that they are charged fully and properly. And there is often a feature to de-sulfate the lead in traditional flooded batteries; that reverses some crystallization that occurs when batteries go unused, extending the battery’s life. These full-featured chargers typically have modes for maintaining a lawn tractor or motorcycle battery, adding to their value.

For those who park outdoors, away from a power source, there are solar-powered battery maintainers. These connect to the car battery, and some cars can be charged via the 12-volt power point inside. Because of their low amperage, a solar unit is used to offset any natural battery discharge, rather than recharge a weak battery. Most solar chargers come with a reverse charge blocking diode to prevent them from draining the car battery at night. Verify that the model you are considering has this feature.

“My preference is a smart battery maintainer,” says John Ibbotson, Consumer Reports’ chief mechanic. “These chargers address a wide range of needs, and they work automatically.”

Ibbotson suggests using quick connectors, often called pigtails. These go onto the battery terminals and allow the charger to quickly plug in and disconnect. Further, they can be safer than clips because they reduce the chance of causing an underhood spark. These eyelet-style connectors often come with smart chargers, or they can be purchased separately.

Before buying, be sure to read the specs for the charger to ensure that it has the features you want. There are many products to choose from, and it can be easy to select one meant for other purposes.