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Battery knowledge

Battery: refers to the device which convert chemical energy into electrical energy by the reaction on the positive and negative electrode.
Primary battery: refers to the batteries which only can discharge, but not for recharging. But the capacity of primary battery is generally greater than that of rechargeable batteries in the same specifications, such as zinc-manganese, alkaline batteries, lithium button batteries, lithium batteries, etc.
Secondary battery: refers to the batteries which can be recharged for cycle use, such as lead acid, nickel-cadmium, nickel metal hydride, lithium ion, lithium polymer, fuel, zinc, aluminum, magnesium-air battery, etc.
Other: fuel cells, physical battery, solar cell.
Rated capacity: refers to the released electrical energy of a fully charged battery which discharge to the cut off voltage under light condition, generally with unit as mAh or Ah (1Ah = 1000 mAh). After using for a long time, the released electrical energy of battery will decline. Due to the charge and discharge under the certain condition of C - rate, the capacity of the battery is directly related to the C - rate. The rated capacity of a battery refers to the electrical capacity tested under the condition of 0.2 C. The greater the C - rate, the smaller the battery discharge ratio. Charging capacity (Ah or mAh) = charging time × charging current, discharge capacity (Ah or mAh) = discharge current x discharge time. In general, 0.2 C current discharge can basically achieve 95% ~ 100% discharge ratio, but 1 C current discharge can only reach about 90% discharge ratio. Because the charging is influenced by the battery raw material characteristics of itself, the charging need more time, about 120% ~ 160% time of current discharge. Take NI MH AA1800mAh for example, charging time takes about 6 ~ 8 hours in 0.2 C (360 mA), but the discharge time is only about 5 hours in 0.2 C (360 mA).
Rated voltage: refers to the potential difference caused by the chemical reaction of the positive and negative electrode materials, the resulting voltage value. Different batteries have different voltage due to different positive and negative electrode materials. The battery voltage will rise to a certain value in the charging process and then fall to a certain value in the discharge process.
Open circuit voltage: refers to battery voltage between the positive and negative electrode in the case without load.
Resistance: refers to the internal impedance of a battery automatically generated by the chemical materials. The smaller the internal resistance is, the better the performance of the battery charge and discharge is. The battery internal resistance includes DC resistance and AC resistance. Influence factors of battery internal resistance are: (1) the composition of the electrolyte; (2) the ingredient formula of the positive and negative electrodes; (3) the geometry size and specific surface area of the positive and negative electrodes; (4) the metal substrate (copper foil and aluminum foil); (5) the interface state of electrolyte with positive and negative electrodes; (6) temperature; (7) charging state (open circuit voltage of the battery); (8) measured frequency; (9) internal structure design of the battery.
C: used to indicate the current ratio of the battery charge and discharge, called as rate. As for a 1200 mAh battery, 0.2 C means 240 mA (0.2 time of 1200 mAh), and 1 C means 1200 mA (1 time of 1200 mAh). Charge and discharge efficiency is also associated with C (rate), under the condition of 0.2 C, charge and discharge efficiency of polymer lithium battery should be 99.8%. Charge and discharge efficiency = discharge capacity/charge capacity × 100%
Discharge cut-off voltage: refers to the voltage achieved after completely discharging for a full charged battery (continuing to discharge is excessive discharge which has great damage to the battery life and performance).
Depth of discharge: the ratio of discharge capacity, compared with the rated capacity of the battery.
Over charge (discharge): refers to exceed the charge or discharge state of the battery regulation, if continue to charge or discharge may cause battery leakage or deterioration.
Energy density: refers to the energy released by unit mass or volume, usually said as the volume energy density (Wh/L) and mass energy density (Wh/kg).
Self-discharge: after a full charge, no contact with the external circuit and placed at normal temperature conditions, the electric capacity of the battery will naturally decrease. In the process of storage, battery capacity will gradually decline, and the proportion of the capacity reduce with the rated capacity is called self-discharge rate. In general, the influence of environment temperature is bigger, too high temperature will accelerate the self-discharge of battery. The self-discharge rate of ordinary nickel cadmium and nickel metal hydride battery is 20% per month, for low self-discharge nickel metal hydride batteries is 2%-3% per month, the self-discharge rate of lithium battery is 2-5% per month.
Cycle life: once charging and discharging of secondary battery is called a cycle. Under certain discharge condition, before the battery capacity falling to a specified value, the cycle times of battery refers to the cycle life. The capacity of the secondary batteries will gradually decline in the use of repeated charging and discharging. Generally taking the rated capacity of the battery as a standard, the charge and discharge times when the battery capacity dropped to 60% or 80% refer to as the cycle life.
Memory effect: battery memory effect refers to the percentage of the next time charging can reach. In order to eliminate the memory effect of the battery, the battery must be first fully discharged before the next time charging. Only in this way, one hundred percent charging can reach. Nickel metal hydride and lithium battery have no memory effect.
CC/CV: CC is constant current, charge or discharge with a fixed current for a battery; CV is constant voltage, charge a battery at a fixed voltage, the charging current will decrease as the voltage rising. For lead-acid battery, generally use the way of constant voltage charging, for nickel cadmium and nickel metal hydride batteries generally adopts the way of constant current charging, for the lithium ion battery generally adopts constant current charging and then constant voltage (4.2V/cell) charging mode.
Trickle charge: Under normal circumstances, it refers to charging with the current less than 0.1 C. When the battery is close to full charge state, the trickle charging mode will be applied for boosting charge. In this case, the battery would have a longer working life.
-△V:When the battery is close to full charge state, the voltage reaches to a peak, keep charging, the voltage will trace down in a very short period of time, generally, the value of -△V between 0 ~ 5 mv. The charging chip can control the battery according to the value of -△V.
△V/△t:When the battery is close to full charge state, the battery surface temperature will rapidly rise over time. The rising temperature per minute can be applied as the condition of charge cutoff, usually set rising 1 degree per minute as the cutoff point.
Charge and discharge rate: the state of charge and depth of discharge are remaining value. Charge and discharge state are expressed using percentage, taking 100% for full charge and full discharge. State of charge is called SOC; depth of discharge is called DOD. For example: DOD=250mAh/800mAh × 100%=31.25%。
The introduction of some kinds of commonly used batteries
1、Alkaline battery(Zinc-MnO2
The full name of this kind battery is alkaline zinc manganese battery. Negative electrode material is zinc powder, positive electrode material is electrolytic manganese dioxide, electrolyte is potassium hydroxide. It has the advantages of large power, strong current, long life, stable output, good low temperature properties, long preservation time, etc., and is widely used in the roll film, flashlight and other attachments in cameras. In general, however, most of the alkaline battery can't be charged and can be used only one time, which results in more expensive cost and pollution to the environment. In fact, alkaline battery is not suitable for driving power of the digital camera. Because the LCD preview, image data processing, zoom lens and shoot of the digital camera all need take a lot of power, which often leads to low power alert when just taking few pieces of photo after installing new alkaline batteries.
2、Nickel-cadmium battery (Ni-Cd)
Nickel cadmium battery, which consists of nickel oxide as the cathode, cadmium oxide as anode and alkaline liquor (mainly potassium hydroxide) as electrolyte, is first applied to devices such as mobile phone, notebook computer batteries, and also used in flashlight and motor roll film of the camera. Although the price is relatively high, it is can be used again after charging, so it is relatively economic for long-term use. The advantages of this kind battery include good large current discharge characteristics and good low temperature performance. The most fatal flaw of nickel cadmium battery: it has serious "memory effect" if there's a misconduct of charging and discharging, which greatly reduces battery life. "memory effect" refers to when charging before the power in the battery is not completely discharged, battery capacity will decrease over time. Of course, we can take the reasonable charge and discharge method to reduce the "memory effect", however, the capacity of nickel cadmium battery with a life of 300-700 times will decline about 20% after charging and discharging for 500 times. In addition, we must pay attention to that the battery internal resistance is small, some of the camera and flash can't use this kind battery so as not to burn electronic circuit components. Beyond that, the cadmium is toxic heavy metal, and it is not conducive to the protection of the ecological environment. So many disadvantages result in that the nickel cadmium battery has been basically eliminated out of the digital camera battery.
3、Nickel metal hydride battery(Ni-MH)
Nickel metal hydride battery, which consists of nickel oxide as the Cathode, hydrogen storage in metal as the anode, alkaline liquor (mainly potassium hydroxide) as the electrolyte, are used as substitute products for early product of nickel cadmium battery. Compared with nickel cadmium battery, nickel metal hydride battery has more advantages. It reduces the "memory effect" of nickel cadmium battery which makes use of Ni-MH batteries is more convenient, and with longer cycle life (up to 1000 times). In addition, the Ni-MH batteries has other obvious advantages, such as high capacity, large depth of discharge, resistance to overcharge and over discharge, short charging time, and so on. Nickel metal hydride batteries do not use toxic heavy metals as raw materials, which can eliminate the pollution to the environment. At the same time, it is similar with alkaline batteries and nickel-cadmium batteries in the electrical characteristics, in practice, it does not need to transform electric equipment such as cameras to use nickel metal hydride battery as substitute.
4.Lithium ion batteries (Li - ion)
Many electric equipment choose lithium ion battery as a power source, which uses embedded lithium compounds as the cathode, carbon materials as anode, lithium non-aqueous organic solvent as battery electrolyte. Though the price of lithium ion battery is quite high, but it has more advantages such as light weight, large capacity, large energy density. In addition, the lithium ion battery has no "memory effect" almost, and does not contain toxic substances etc., this is the main reason for its wide application. But the safety performance is poor.
Secondary battery charging way: in general, slow charge way is well advised to choose, which can extend battery life. If quick charge is often used, after a period of time, several times slow charge should be carried out in order to maintain battery. In addition, a new rechargeable battery power usually has very low or no electricity, lithium-ion batteries can be charged directly or after fully discharging. Ni-MH batteries can be optimally charged after running out of power, and nickel cadmium battery must be charged only after run out of electricity. The charging time depends on the charger and batteries. Lithium ion batteries will be charged subject to supporting the charger tip; Ni-MH/Ni-Cd battery can be charged subject to the charger tips, but if the charger without tips, need to calculate the charging time: the first thing is to figure out the minimum capacity of Ni-MH/Ni-Cd battery (mAh) and the charging current of charger (mA),
Charging time = minimum battery capacity ÷ charging current x 1.1
Make the necessary cleaning for batteries: Keep a good contact with batteries and electric, it is necessary for cleaning the battery. Keep the contact point at the ends of the battery and battery cover internal clean. It is necessary to use soft, dry cloth gently to wipe clean, never use something with solubility that such as chemical reagent to clean your digital camera battery compartments, anode and cathode of battery and the charger contact.
Preservation of the battery: when you do not use electrical appliances for a long time, must remove battery from electrical appliances and store them in a dry and cool environment (< 28 ℃), and not put the battery and the metal objects (such as keys, paper clips, nails, etc.) together in order to prevent the short circuit. For storage, Nickel cadmium /Nickel-metal hydride batteries should take full charge, and use once after 3 months of storage, and then fully charged and storage. If battery is low self-discharge, it can store 1-3 years without processing. The battery can be pasted using transparent tape before storage when skin of battery is damaged, otherwise the battery will be short circuit, especially cylindrical battery.
Different types of battery cannot be mixed for use;
The battery with different charging status cannot be mixed for use, secondary battery cannot be used at the same time of charging;
The battery with different capacity cannot be mixed for use;
The old and new batteries cannot be mixed for use.