Trustworthy reviews and/or ratings of auto battery chargers are on Amazon.com as of 2015. The popular retail website features a wide selection of chargers and many concusmer reviews.
The Schumacher charger shows a rating of 4.3 stars out of five stars, as of Novermber 2015, based on 1,200 customer reviews and 173 answered questions. A customer boasts that this charger does not affect a good battery while it charges a dead battery. Another reviewer is pleased the Schumacher goes beyond expectations and is worth the price. The customer reported that the battery improved to 98 percent and it maintains the battery of a car that is not being driven.