Do Lead-acid Batteries Have Memory Effects
Battery memory effect refers to the phenomenon that if the Battery belongs to nickel-cadmium Battery, if it is not fully charged and discharged for a long time, it is easy to leave traces in the Battery and reduce the Battery capacity.
Battery memory effect means that the battery seems to remember the user's daily charging and discharging range and mode, and it is difficult to change this mode after a long time, and can't do a large charge or discharge. Lithium-ion batteries do not have this effect.
causation
Because of the negative electrode sintering in the traditional process, the cadmium grains are relatively thick. If nickel-cadmium batteries are recharged before they are completely discharged, the cadmium grains are easy to aggregate into a block, thus forming a secondary discharge platform when the battery is discharged.
The battery stores this discharge platform and USES it as an end point for the next cycle, although the capacity of the battery itself allows the battery to be discharged to a lower platform. 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 becomes lower.
Cognitive memory effect
Battery memory effect refers to the reversible failure of a Battery, i.e. the capability of the Battery to recover after failure. Batteries maintain this tendency automatically when subjected to a particular cycle of work over a long period of time. This was first defined in nickel-cadmium batteries, nickel-cadmium bag-type batteries have no memory effect, sintered batteries have memory effect. This means that the battery seems to remember the user's daily charging, discharging range and mode, and it is difficult to change this mode after a long time, and it can no longer do large charging or discharging. However, the current nickel-metal hydrogen (commonly known as nickel-metal hydrogen) battery is not subject to the definition of this memory effect, but has inertia, the first few times to activate it, generally can charge and discharge 300-500 times, after which you will find the duration is getting shorter and shorter, so short that you want to change your mobile phone. Wrapping an old battery in a freezer for a few days and then using it again will improve performance.
Because of the negative electrode sintering in the traditional process, the cadmium grains are relatively thick. If nickel-cadmium batteries are recharged before they are completely discharged, the cadmium grains are easy to aggregate into a block, thus forming a secondary discharge platform when the battery is discharged. To eliminate this effect, there are two methods, one is to use a small current depth discharge (such as 0.1c to 0V), one is to use a large current charge and discharge (such as 1C) several times.
In practical application, the method of eliminating memory effect has strict specification and an operation flow. Improper handling can backfire. For nickel cadmium battery, the maintenance of normal is deep discharge on a regular basis: the average use for a month (or 30 times circulation) on a deep discharge (discharge to 1.0 V/per day, namely exercise), common use is to use photovoltaic cells or use the means such as shutdown can reduce the formation of the memory effect, but this is not exercise, because the instrument (such as mobile phone) is not used 1.0 V/only to turn it off every day, must be special equipment or line to finish the work, fortunately, many of nimh battery charger with this function. The battery stores this discharge platform and USES it as an end point for the next cycle, although the capacity of the battery itself allows the battery to be discharged to a lower platform. 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 becomes lower.
Lithium ion battery
The anode of a lithium-ion battery is usually made up of active lithium compounds, while the anode is carbon with a special molecular structure. The common positive electrode material is mainly composed of LiCoO2. When charging, the potential added to the battery poles forces the compound of the positive electrode to release lithium ions, which are embedded into the carbon with the negative electrode molecules arranged in a lamellar structure. At discharge, the lithium ions are separated from the lamellar carbon and recombined with the anode compound. The movement of lithium ions generates electric current. Although the principle of chemical reaction is very simple, there are still many practical problems to be considered in practical industrial production. The electrolyte filled between the positive and negative electrodes, in addition to maintaining stability, also needs to have good electrical conductivity, reduce the internal resistance of the battery.
Lithium-ion batteries typically come with a management chip and a charging control chip. In the management chip, there are a series of registers, which contain the capacity, temperature, ID, charging state, discharge times and other values. These values vary over time. The main function of the instruction "it should be fully charged and discharged once every month or so" should be to correct the improper values in these registers, so that the battery charging control and nominal capacity match the actual situation of the battery. The charging control chip mainly controls the charging process of the battery. The charging process of a lithium-ion battery is divided into two phases: constant current fast charge (when the battery indicator is yellow) and constant voltage current decline (when the battery indicator is green).
In the constant current quick charging stage, the battery voltage gradually increases to the standard voltage of the battery, and then it is transferred to the constant voltage stage under the control chip. The voltage no longer increases to ensure that there is no overcharge, and the current gradually weakens to zero with the increase of the battery power, and finally the charging is completed. The Battery statistics chip can sample and calculate the Battery capacity by recording the discharge curve (voltage, current and time). This is the wh value we read in Battery Information. However, the discharge curve of a lithium-ion battery will change after repeated use. If the chip does not have the opportunity to read out a complete discharge curve again, the calculated power will be inaccurate. So we need a deep charge to calibrate the battery chip.
1. Does the new battery need to be recharged and discharged several times to be activated?
Because lithium-ion batteries have no memory effect, they need not be activated. Some rechargeable batteries do require a similar "activation" job. These were the earlier nickel-cadmium and nickel-hydrogen rechargeable batteries. These cells produce a phenomenon known as the "memory effect", in the condition of incomplete discharge of charge, easy to make a battery overcharge, after a long time can lead to hyperplasia of crystal plate electrode, blocking the contact with the plate electrode, electrolyte battery voltage drop, let users having the feeling that the battery soon ran out. For both types of batteries, recharging the battery after it has been fully discharged at regular intervals (rather than each time) can reduce the voltage drop caused by the above reasons. But most of the batteries used in our phones and laptops today are li-ion batteries. Lithium-ion batteries, which are small but can store large amounts of energy, are becoming more widely used. Lithium ion batteries do not require deep charge and discharge to be activated at the beginning of use, because the battery initialization and testing process has been completed in the manufacture of the battery. Lithium-ion batteries also have no so-called "memory effect" and can be recharged at any time. The idea of a regular full charge and discharge of a lithium-ion battery is simply to calibrate the battery detectors in laptops and some high-end smartphones, not because it's good for the battery itself. For ordinary mobile phones, digital cameras, such as segmented display of roughly the amount of battery equipment, is completely do not need regular full charge and discharge.
2. Can overcharging cause battery explosion?
Lithium ion battery energy density is big, high voltage (single lithium ion battery cell voltage 4.2 V, and ordinary nickel-based rechargeable battery is 1.2 V), and low voltage class compared to batteries, lithium ion battery electrodes with the REDOX reaction of very severe, so the use of lithium ion battery conditions must be tightly restricted, overcharge, excessive discharge and short circuit, high temperature can cause cell damage, even fire and explosion. However, the actual use of lithium ion battery is a number of cells together with a set of safety protection circuit and a variety of safety devices packaged into a panel. These safety features ensure that the battery's circuits are automatically cut off during overcharging, overdischarge, and short circuits. Excessive pressure inside the battery will also trigger the exhaust device to reduce pressure; Too high a battery temperature can trigger a hot-melt protector that blocks the movement of lithium ions and thus stops the battery's electrochemical reaction. So, as long as you don't use fake batteries of dubious quality, it won't explode if you don't unplug your phone before it's fully charged.
3. Can the battery life be extended by reducing the number of charges?
The life of a lithium ion battery can reach several hundred cycles of charge and discharge. A charge cycle is the process of using up and then recharging the battery, rather than plugging it in and unplugging it once. Continuous deep charge and discharge of lithium ion battery has an impact on the life of lithium ion battery. The above data of hundreds of times are also measured under such conditions. However, the life of lithium ion battery is actually quite long under the condition of daily shallow charge and discharge. In addition, lithium ion batteries do not use, its capacity will be a natural loss, the main factors are voltage and temperature. The results show that the storage capacity of lithium ion in the state of full charge for a long time will suffer obvious loss. Similarly, the higher the temperature, the faster the lithium-ion battery loses capacity, and this loss is irreversible, meaning the battery loses capacity permanently. At zero degrees Celsius, the remaining 40 percent of a lithium-ion battery loses 2 percent of its capacity after a year of storage. Fully charged lithium-ion batteries lose 35% of their capacity after a year at 40 degrees. 4. Proper use of lithium-ion batteries
1. Charge the new battery:
In the use of lithium battery should be noted that the battery after a period of time will enter the dormant state, at this time the capacity is lower than the normal value, the use time will also be shortened. But lithium battery is very easy to activate, as long as after 3-5 normal charge and discharge cycle can activate the battery, restore the normal capacity. Due to the characteristics of lithium battery itself, it has almost no memory effect. Therefore, users do not need special methods and equipment in the activation process of new lithium batteries. The "natural activation" of a standard charging method from the beginning is best. Lithium batteries or chargers automatically stop charging when the battery is fully charged, and there is no such thing as a "trickle" of nickel chargers that lasts for more than 10 hours. In other words, if your lithium battery is fully charged, it will go blank on the charger.
And none of us can guarantee that the characteristics of the battery charge-discharge protection circuit will never change and the quality is foolproof, so the battery will be in danger for a long time to wander around the edge. This is another reason we oppose long - term charging. In addition, on some machines, if the charger is not removed after charging for a certain period of time, the system will not only not stop charging, but also start the discharging - charging cycle. This may serve a purpose, but it is clearly bad for battery life. At the same time, long charging takes a long time and often takes place at night. In China's power grid, the voltage at night is relatively high and fluctuates greatly in many places. Having said that lithium batteries are delicate, they are much less resistant to fluctuations in charge and discharge than nickel ones, which poses additional risks.
2. When to start charging in normal use:
Since the number of charges and discharges is limited, lithium batteries should be used up and recharged as much as possible. Regarding the experimental table of charge and discharge cycles of lithium ion batteries, the data of cycle life are listed as follows: cycle life (10%DOD) : "1000 cycle life (100%DOD) :" 200 times
DOD stands for discharge depth. As can be seen from the table, charging times are related to discharge depth, and the cycle life of 10%DOD is much longer than that of 100%DOD. , of course, if the conversion to the actual charge relative to the total capacity: * 1000 * 200 = 200 = 100100%, 10% of the latter to fully charge and discharge is still relatively good, under normal circumstances, there should be a reservation according to the principle of battery remaining power run out to refill charging, but if the battery in expected to 2 days can't insist on the whole during the day, it should start charging in a timely manner, of course, if you are willing to carry the charger to the office when BieLun again.
When charging is needed to cope with the important event that is expected to lead to busy communication, even if the battery still has a lot of power, it is necessary to charge in advance, because there is no real loss of "1" charge cycle life, that is, "0". X "times, and it tends to be small. The principle of recharging a battery after it has run out of charge is not to go to extremes. As widespread as long charging is, "try to use up your machine's battery, preferably by shutting it down automatically." This is really just a nickel battery, designed to avoid memory effects, but unfortunately it also works on lithium batteries. There have been examples of people who continue to use a machine without charging after warnings that the battery is too low. As a result, the machine in this example did not respond in the later charging and starting up, and had to be sent to customer service for maintenance. In fact, this is because the battery voltage is too low due to excessive discharge, so that it does not have the normal conditions for charging and starting up.
3, the correct approach to lithium battery
To sum up, my most important tips on the charging and discharging problems of lithium batteries in use are as follows:
1. Charge according to standard time and procedure, even the first three times;
2, when the machine power is too low, should try to timely start charging;
3. No special method is required for the activation of lithium battery, which will be activated naturally in normal use of the machine.
[1] lead-acid batteries in battery cars generally have no memory effect. Generally speaking, zincate is the easy memory effect of nickel acid. Lead battery of battery car is shown as follows:
[2] Definition: Electrodes are mainly made of lead and its oxides, and electrolyte is a kind of battery for sulfuric acid solution. English: Lead-acid battery. In the discharge state, the main component of the positive electrode is lead dioxide, and the main component of the negative electrode is lead; in the charge state, the main component of the positive and negative electrode is lead sulfate. It is divided into exhaust battery and maintenance-free lead-acid battery.
[3] The battery is mainly composed of tubular positive plate, negative plate, electrolyte, separator, battery cell, battery cover, pole, injection cover, etc. The electrodes of exhaust batteries are composed of lead and lead oxides, and the electrolyte is an aqueous solution of sulfuric acid. The main advantages are voltage stability and low price; the disadvantage is low specific energy.
