If the battery charger is not properly connected to the battery terminals, charging will not takes place. If the terminals, connecting clips etc are dirty or corroded, current will not pass into the battery. So even after prolonged charging, the battery will not attains full charge. The only way to confirm the flow of current is to connect an ampere meter in series with the positive so that when current passes, the needle deflects based on the amount of current passing. Here an LED indication is used to confirm the current flow into the battery.
Filed Under: Electronic Projects