The Danger of Overcharging NiCad Batteries

The charging technique just described will work only as long as the overcharging current is limited to a value such that the rate of oxygen liberation at the anode is less than or equal to the rate of diffusion across the separator. If the overcharging current is too high, excess oxygen is produced at the anode. And since not enough oxygen can diffuse across to make up for the reduction at the cathode, the excess cadmium hydroxide is used up. Hydrogen is then formed. This leads to a dangerous situation, due to both fire and overpressure. Cells are designed to vent when this condition occurs, releasing the excess hydrogen and oxygen to the air before bad things happen. While this may keep cells from blowing up, it does damage them, since the cell is losing material. Further, it upsets the chemical balance inside the cell; in other words, if the cells lose enough water, they stop working. Another problem is the heat that is produced by the process of generating oxygen and recombining it at the cathode. With a moderate amount of current, the cell temperature can rise considerably to 50 or 60 degrees Celsius (122 to 140 degrees Fahrenheit). If, after charging, the batteries are hot, then you have overcharged them.

Just remember, charge control is the key to proper battery management. More batteries are destroyed or damaged by bad charging techniques than all other causes combined. Once a battery reaches full charge, the charging current has to go somewhere - most often generating heat and gases. Both are bad for batteries.

DIY Battery Repair

DIY Battery Repair

You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.

Get My Free Ebook


Post a comment