The "memory effect", as the name suggests, is that when the battery is not used up on the charge, it will be here to leave a "memory", when you fully charged and then used, once used here, it will warn no power, and then stop working. Although the real reason for the memory effect of NiCd batteries is not very clear, but people have summed up some methods about the correct use of NiCd batteries and the elimination of their memory effect in their long-term work practice.
Interpretation of battery memory effect
Battery memory effect refers to the phenomenon that if the battery is a nickel-cadmium battery, long-term incomplete charging and discharging, easy to leave traces in the battery, reducing the capacity of the battery. The battery seems to remember the user's daily charging and discharging amplitude and pattern, and it is difficult to change this pattern after a long time, so it cannot do substantial charging or discharging again.
The memory effect is most obvious for NiCd batteries. When each charge, there is cadmium hydroxide in the negative electrode and electrode action, producing metal cadmium and deposited on the negative electrode surface. When discharged, the cadmium metal on the surface of the negative electrode reacts to form cadmium hydroxide, and when charging and discharging is incomplete, the cadmium metal inside the electrode will slowly produce large crystals and cause the subsequent chemical reaction to be hindered, resulting in reduced capacity, which is the cause of the so-called "memory effect".
Causes of battery memory effect
As the negative electrode is sintered in the traditional process, the cadmium grains are coarse, if the NiCd battery is recharged before they are completely discharged, the cadmium grains tend to agglomerate into a block and form a secondary discharge platform when the battery is discharged.
The battery will store this discharge plateau and use it as the end of discharge in the next cycle, although the capacity of the battery itself allows the battery to discharge to a lower plateau. The battery will only remember this low capacity during subsequent discharges. Also in each use, any incomplete discharge will deepen this effect, making the battery capacity even lower.
Removal method of memory effect of NiCd battery
Nickel-cadmium batteries will produce a memory effect if they are not completely discharged in use. Although a simple resistor can be used to completely discharge the battery, if no special measures are taken, the battery will run the risk of over-discharging, when the polarity of the battery will be reversed.
To eliminate this effect
Step 1: Overcharge. Take the normal charging method to reach a full battery charge, specifically by overcharging. Generally chargers work with constant current, and the time required for charging can be calculated based on the charging current line. For example, when the battery capacity is 600 mA, the charging current is 100 mA = 6 hours, if the overcharge may wish to add another 2 hours, charging to 8 hours.
Step 2: Overcharge. After the battery is overcharged, then use a higher current, such as 500 mA, to discharge the battery to the termination voltage, and then switch to a small current, such as 50 mA, discharge to the empty state.
Step 3: Slow charge. Charge the fully discharged battery with a small current trickle for more than 20 hours, and then discharge normally according to the regular discharge procedure.
For NiCd batteries, the normal maintenance is regular deep discharge, on average, every month of use for a deep discharge, the normal use is to try to use the light battery or used to shut down and other means can ease the formation of memory effects, but this is not, because the instrument is not used to 1.0V / per section before shutting down, must be special equipment or lines to complete the work.
If you want to speed up the process of discharging the battery, you can use multiple LEDs in parallel with LED1 to increase the load. If the discharge of the battery memory effect is still in doubt. You can charge and discharge the battery several times in a row to see if there is still a memory effect. After this discharge process, the NiCd battery will be able to restore the original capacity.
Memory effect is the tendency of the battery to automatically maintain this specific battery performance after a specific work cycle. It is a phenomenon of the battery characteristics, is a temporary failure, take some measures, is possible to restore the original characteristics.
