What are the charging methods for Ni-MH batteries

After the Ni-MH battery is fully charged, if the fast charging is not stopped in time, the temperature and internal pressure of the battery will rise rapidly. When the internal pressure is too high, the sealed battery will open the vent hole, thereby allowing the electrolyte to escape, causing the viscosity of the electrolyte to increase, the internal resistance of the battery, and the capacity to decrease. Therefore, in order to ensure that the battery is fully charged without charging, the end of the charge must be controlled, and various methods such as on-time control, voltage control, and temperature control are generally used. How to charge the Ni-MH battery In the first stage, when the constant current is just charged into the discharged Ni-MH battery, the battery voltage rises quickly (point A) due to a voltage drop in the internal resistance of the battery. After that, the battery begins to receive charge, and the battery voltage continues to rise at a lower rate. In this range (between AB), the electrochemical reaction produces oxygen at a certain rate, and oxygen also combines with hydrogen at the same rate. Therefore, the temperature and gas pressure inside the battery are very low. After a press time in the second stage, bubbles begin to appear in the electrolyte. These bubbles are concentrated on the surface of the electrode plate, reducing the effective area of u200bu200bthe electrode plate, so the internal impedance of the battery increases, and the battery voltage begins to rise faster. This is a signal close to full power. After the third stage is fully charged, the current charged into the battery is not converted into battery energy storage, but oxygen appears on the positive plate. Oxygen occurs due to the electrolysis of electrolyte. In the electrolyte composed of potassium hydroxide and water, hydroxide ions become oxygen, water and free electrons. The reaction formula is 40H-→O21+2H0+4e- although the oxygen that appears in the electrolyte can quickly be on the surface of the negative plate. Recombination in the electrolyte, but the temperature of the battery still rises significantly. In addition, since the charging current is used to generate oxygen, the pressure in the battery also rises. Since oxygen is easily analyzed from a large amount of hydroxide ions, the temperature in the battery rises sharply, which causes the battery voltage to drop. Therefore, the battery voltage curve has a peak. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: What are the design uses of the lithium battery protection board