Battery technology training materials Secondary battery use and
maintenance:
●Temperature characteristics: Since the migration rate of rechargeable
batteries in electrolyte liquid and electrode sheets is closely related to
temperature, fluctuations in temperature will significantly affect the technical
performance of rechargeable batteries.
●Storage temperature: Under normal circumstances, due to the liquid inside
the battery, long-term storage at low temperatures will destroy the internal
chemicals of the battery. Therefore, it is recommended that the storage
temperature should not be lower than -20°C if conditions permit; and too high a
temperature will also To prevent the battery from reaching its rated capacity,
the general storage temperature should not be higher than 40°C. The normal
storage temperature of rechargeable batteries is -20℃~+65℃. When the temperature
drops below -20℃, the electrolyte in the battery will solidify, the internal
resistance of the battery will become infinite, and the battery will become
unusable. When the temperature exceeds +65°C, the electrolyte will undergo side
reactions to produce a large amount of gas, and the resin adhesive in the
electrode sheets will also deteriorate, causing the entire battery to gradually
age and decline, and even fail in the short term.
●Charging temperature: Under normal circumstances, the charging temperature
is 0℃~45℃.
●Discharge temperature: Under normal circumstances, the discharge
temperature is -20℃~65℃; but in some special cases, low-temperature batteries
and high-temperature-resistant batteries can be used.
●Battery packs are generally discharged before leaving the factory to
prevent short circuits due to shock or other reasons during transportation.
Usually new batteries are not charged or only contain about 20% of the
power.
●New batteries or batteries that have not been used for a long time may not
be fully activated due to the active material. They generally need to undergo
two or three cycles of small current (0.1C) charge and discharge before use to
reach the nominal capacity.
●Battery that is not used for a long time should be stored in a state of
charge. Generally, it can be precharged to 50% to 100% before storage. It is
recommended to charge the battery once every three months to restore it to
saturated capacity.
●Precautions for battery use: △Do not incinerate or disassemble the
battery. The chemicals in it are corrosive and can damage the skin and eyes. △Do
not pull the battery leads or plugs to prevent damage to the solder joints and
connection parts. △Battery types of different types cannot be mixed. △When
welding different types of batteries, connecting pieces etc. need to be used for
welding. △Fully charge with a small current before first use. △Do not charge in
parallel, otherwise irregular charging current will occur. △Do not use the
battery in reverse or short-circuit it. △After the battery is fully discharged,
the charging time should be extended to reach saturation. △Please store the
battery in a cool, ventilated and dry environment with a temperature no higher
than 45°C. △Do not store a large number of batteries densely when the batteries
are fully charged or half full. △Do not come into contact with acidic gases and
avoid being close to fire sources. Battery noun:
●Battery: refers to a device that converts chemical energy into electrical
energy through the reaction between positive and negative electrodes.
●Primary battery: refers to a battery that cannot be charged and can only
be discharged. However, the capacity of a primary battery is generally greater
than that of rechargeable batteries of the same specifications, such as
zinc-manganese, alkaline dry batteries, lithium button batteries, lithium
sub-batteries, etc.
●Secondary battery: refers to batteries that can be repeatedly charged and
recycled, such as lead-acid, nickel-cadmium, nickel-metal hydride, lithium-ion,
lithium-polymer, fuel, zinc, aluminum, magnesium-air batteries, etc.
●Rated capacity: refers to the electrical energy that the battery can
release when it is fully charged and discharged to the cut-off voltage under
no-load condition. It is generally expressed in mAh or Ah (1Ah=1000mAh) symbols.
However, if the battery is connected to a load and used for a long time, the
power released by the battery will decrease. Capacity Since charging and
discharging are performed under certain C-rate conditions, the capacity of the
battery is directly related to the C-rate. Normally, the nominal capacity of a
battery refers to the capacitance measured under 0.2C conditions. The greater
the C-rate, the smaller the discharge rate of the battery. Charging capacity (Ah
or mAh) = charging current × charging time, discharge capacity (Ah or mAh) =
discharge current × discharging time. Generally speaking, a 0.2C current
discharge can basically reach a discharge rate of 95% to 100%, while a 1C
current discharge can only reach about 90% discharge rate. Since charging is
affected by the characteristics of the battery raw materials, it requires a
longer charging time, roughly. It is 120~160% of the discharge time of the same
current. For example, NI-MHAA1800mAh takes about 6~8 hours to charge at 0.2C
(360mA), and it can take about 5 hours to discharge at 0.2C (360mA).
●Rated voltage: refers to the potential difference between the positive and
negative electrode materials of the battery due to chemical reactions, and the
resulting voltage value. Different batteries produce different voltages due to
different positive and negative electrode materials, such as lead-acid: 2V/cell,
nickel-cadmium and nickel-hydrogen: 1.2V/cell, lithium-ion battery: 3.6V/cell.
In addition, the battery voltage will continue to rise to a certain value with
the charging process, and will continue to drop to a certain value with the
discharging process.
●Open circuit voltage: refers to the voltage of the battery when it is not
connected to an external circuit or external load. There is a certain
relationship between the open circuit voltage and the remaining energy of the
battery. Therefore, the battery display of the mobile phone is made using this
relationship.
●Internal resistance: refers to the resistance automatically generated by
chemical materials inside the battery. Generally speaking, the smaller the
internal resistance, the better the battery’s charge and discharge performance.
Battery internal resistance is a very complex and important characteristic, also
known as battery impedance, including DC resistance and AC resistance. The
factors that affect the internal resistance of the battery are: ① the
composition of the electrolyte; ② the ingredient formula in the positive and
negative electrode sheets, such as the content of conductive carbon powder; ③
the geometric area and specific surface area of the positive and negative
electrode sheets; ④ the metal substrate (copper foil and Aluminum foil); ⑤The
interface state between the electrolyte and the positive and negative electrode
sheets; ⑥Temperature; ⑦Charging state (open circuit voltage of the battery);
⑧Measurement frequency; ⑨The internal structure design of the battery.
●C: Used to express the ratio of current when charging and discharging the
battery, that is, the rate. For example, for a 1200mAh battery, 0.2C means 240mA
(0.2 times 1200mAh), and 1C means 1200mA (1 times 1200mAh). Charge and discharge
efficiency Charge and discharge efficiency is also related to C (rate). Under
0.2C conditions, the charge and discharge efficiency of polymer lithium
batteries should be 99.8%. Charge and discharge efficiency = discharge
capacity/charge capacity × 100%
●Discharge cut-off voltage: refers to the voltage reached when the battery
is fully charged and discharged (if it continues to discharge, it is
over-discharge, which will greatly damage the life and performance of the
battery). Generally speaking, lead-acid batteries: 1.8V/cell, nickel-cadmium,
nickel-metal hydride: 1.0V/cell, lithium-ion battery: 2.75V/cell.
●Open circuit voltage: refers to the voltage between the positive and
negative electrodes of the battery when there is no load.
●Depth of discharge: the ratio of discharge capacity compared with the
rated capacity of the battery.
●Overcharge (discharge): refers to exceeding the specified charge
(discharge) state of the battery. Continuing to charge (discharge) may cause
battery leakage or deterioration.
●Energy density: refers to the energy released per unit volume or unit
mass, generally expressed by volume energy density (wh/l) and mass energy
density (wh/kg).
●Self-discharge: After the battery is fully charged, its capacitance will
naturally decay when it has no contact with external circuits and is placed at
room temperature. During the storage process, the battery storage capacity will
gradually decrease, and the ratio of the reduced capacity to the rated capacity
is called the self-discharge rate (nickel-cadmium and nickel-metal hydride
batteries have a larger self-discharge rate than lithium-ion batteries).
Usually, the ambient temperature has a greater impact on it, and excessive
temperature will accelerate the self-discharge of the battery. The expression
method and unit of battery capacity decay (self-discharge rate) is: %/month. The
self-discharge rate of nickel-cadmium and nickel-metal hydride batteries is
20-25%/month, and the self-discharge rate of lithium batteries is
2-5%/month.
●Cycle life: A secondary battery undergoes a charge and discharge called a
cycle or cycle. Under a certain discharge system, the number of cycles the
battery undergoes before the battery capacity drops to a specified value is
called cycle life. When the secondary battery is repeatedly charged and
discharged, the battery capacity will gradually decrease. Generally, the rated
capacity of the battery is used as the standard. When the battery capacity drops
to 60% or 80%, the number of charges and discharges is called cycle life.
●Memory effect: The memory effect of a battery refers to the percentage of
a fully discharged battery that can be charged the next time. In order to
eliminate the memory effect of the battery, it must be completely discharged and
then recharged before charging in the second half. Only by doing this can the
battery be fully charged. The memory effect of the battery brings inconvenience
to the rapid charging of the battery. If the nickel-cadmium battery is charged
without being fully discharged, the capacity may not return to the original
standard, but it can be recharged with high current after deep discharge, and
the capacity may be restored. Both nickel metal hydride and lithium batteries
have no memory effect.
●CC/CV: CC means constant current, charging (discharging) the battery with
a fixed current; CV means constant voltage, charging the battery with a fixed
voltage, and the charging current will decrease as the voltage increases.
Lead-acid batteries are generally charged in constant voltage mode,
nickel-cadmium and nickel-metal hydride batteries are generally charged in
constant current mode, and lithium-ion batteries are generally charged in
constant voltage (4.2V/cell) and then constant current mode.
●Trickle charging: refers to charging the battery with a current less than
0.1C. It is generally used for supplementary charging when the battery is nearly
fully charged. In addition, if the load does not have strict requirements on
charging time, it is recommended to use trickle charging (in In this case, the
battery life is longer).
●-△V: This is the characteristic during the charging process of
nickel-cadmium and nickel-metal hydride batteries (that is, when the battery is
nearly fully charged, after the voltage reaches a peak value, if you continue to
charge it, the voltage will drop momentarily, usually within 3~ Between 5mV, the
charging chip mostly controls the battery based on the -△V value.
●△V/△t: This is another characteristic of the charging process of
nickel-cadmium and nickel-metal hydride batteries (that is, when the battery is
nearly fully charged, the battery surface temperature will rise rapidly over
time, and the temperature rise per minute is used as the The charging cut-off
condition is generally set at a rise of 1 degree per minute as the cut-off
point.
●Charge and discharge rate (State of charge, Depth of discharge), state of
charge and depth of discharge are both methods of expressing the number of
batteries retained. The charge and discharge status is expressed as a percentage
rate, with full charge and full discharge being 100%. The state of charge is
called SOC; the depth of discharge is called DOD. For example:
DOD=250mAh/800mAh×100%=31.25%
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