NiMH and NiCad Batteries Fast Charger Circuit with PIC Microcontroller

Fast charging circuit with PIC16F88 microcontroller can work with dc voltage between 7-30 volts. PIC16F88 used for control can fast charge NiMH and Nicad batteries whose supply is provided with LM317T. When the batteries are full, automatic charging is interrupted. There is heat protection with thermistor. The highest charging current is 2.5a.

Quick Charger for NiMH and Nicad Batteries This is a truly versatile charger. It can charge up to 15 identical NiMH or Nicad cells. You can build it to fit any size cell or cell capacity and adjust the charge rate. It can charge fast, slow charging and has protections including temperature detection to prevent overcharging.

Standard NiMH and Nicad chargers typically only charge two or four AA cells and at a fairly slow rate – typically taking four to 15 hours to charge. But what if you want to charge at a much higher rate or more than four cells at once?

The circuit can charge from one cell up to 15 cells at the same time and its voltage is up to 18V for both NiMH and Nicad types. Charging is adjustable from just a few milliamps to 2.5A and includes reliable end-of-charge detection with extra protections to prevent overcharging.

Safety is important when charging NiMH and NiCad cells and batteries; because if the charger is left on for too long after the battery pack is fully charged, they can be destroyed or their lifespan can be severely shortened.

Continuous overcharging will damage cells due to high temperature. This speeds up the chemical reactions that contribute to the aging process. In extreme cases during overcharge, excessive internal pressure can open the safety holes to release the pressure. These holes will close again after the pressure is released, but the cells will have already been damaged.

PIC16F88 Fast Charger Circuit

Source: http://www.siliconchip.com.au/cms/A_109188/article.html

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