To operate a Battery Tender Plus car charger, first connect the charger to the battery. The charger is fully automatic and can be connected to AC power and the battery for extensive time periods, though instructions recommend that you check the charger and battery periodically for proper operation. The car charger has two status lights -- red and green -- indicating the mode of the charger and the battery's condition, so you can check the status of your battery easily.
The Battery Tender Plus car charger self-monitors the battery and keeps it in full charge when connected. It also has short circuit protection and reverse polarity protection that are functional even when you are not monitoring the battery and charger.
These chargers operate in three modes: bulk, absorption and storage maintenance. When your battery has reached a full charge, the green light appears, indicating that the charge has completed, and the charger then goes into storage mode.
The Battery Tender car chargers come in models that charge at rates of either 5.0 or 2.5 amps per hour, meaning that a 15-amp-hour battery takes two to five hours to recharge. Large marine batteries and other deep cycle batteries can take more than one full, 24-hour day to charge completely.