Smart Battery Charger

This unit was constructed in the shell of a Radio Shack battery charger.  The original unit charged only one type of battery at a time and only in pairs.   This unit allows for mix and match for AAA, AA, C, and D cells.  Each battery is individually monitored and charged.   An LED for each one flashes to show the current charging condition as follows....
 

• Dim with bright flash: No battery detected
• Solid on: Battery charging
• Blinking on: Battery charged

When a battery is first inserted, a small charge is pulsed to it.  In between the pulses, the battery is tested for voltage.  This prevents the unit from attempting to charge shorted or really dead batteries.  If and when a voltage is detected, the unit begins normal charging.