Battery Chemistries
Lipo Battery
BOKA LiPo Rechargeable Battery Data Sheets Tables
1.LiPo Rechargeable Battery Data Sheets Table.
Overview
Generally speaking, polymer materials are non-conductive. The conductivity of traditional solid polymer electrolyte is very poor. This limits the scopes of its applications. The key technology of our Lipo batteries is using PVDF-HFP as the main polymer material, which thoroughly absorbs electrolyte and raises the conductivity very close to that of the liquid electrolyte, then successfully avoiding electrolyte leakage problem. Thanks to no free liquid electrolyte, there is no need of outer metal can for packaging. Therefore, the thickness of the battery has no lower limit. It can also fulfill the desires of “light-weight, thin, short, and small” electronic products. It can be easily tailored according to the designs and this would greatly enhance the added-values of products.
LiPo Battery Features
1.No Electrolyte Leakage Problem
Traditional battery electrolytes are liquid solutions such as aqueous solutions or organic solvents. Any tiny crevices would cause electrolyte leakage problem. If the electrolyte is a strong acid or strong base, it would further cause product failure. The electrolyte in Lipo batteries is thoroughly absorbed in the polymer matrix. No free liquid electrolyte exists. Therefore, there is no electrolyte leakage problem.
2.Development Toward Thinner Batteries
The thickness of the Lithium polymer battery can be as thin as 0.6mm. Because it contains no free liquid electrolyte, there is no need for metal outer cans. It only takes 0.1mm thick Al laminate film to pack the battery. As to the increase in capacities of the batteries it can be accomplished by stacking multiple bicells or enlarging the battery areas.
3.Better Battery Design Flexibility
The size of developed Lipo Batteries can be as small as stamps, name cards, or as large as paper size A4 or A5. They can be of triangle or donut shapes, regardless of the costs. Product designers do not have much flexibility in adopting traditional Li-ion batteries because of the limitations on the choice of battery dimensions. However,the presence of Lipo batteries’ unique feature in size flexibility provides the designers more space for creativity.
4.Light-weight and Low Cost
Lipo battery not only possesses small volume, but also saves the heavy metal container and complicated cap, naturally lowering a lot of weights. This promotes the specific energy density and reduces the battery materials cost a great deal. Also the excellent manufacturability of the Lipo batteries can expectedly lower the manufacturing cost as well.
Characteristics of BOKA Li-ion Polymer Battery
1.Charge Characteristics
Fig.4 Charge Characteristic(LP-433562)
2.Discharge Rate Characteristics
Fig.5 Discharge Rate Charateristics(LP-433562)
3.Temperature Discharge Characteristics
Fig.6 Temperature Discharge Characteristics(LP-433562)
4.Charge/Discharge Cycle Characteristics
Fig.7 Charge/Discharge Cycles Characteristics(LP-433562)
5.Cycles Number V.S Internal Impedance
Fig.8 Cycles V.S Internal Impedance(LP-433562)
6.Cycle Life Characteristics
Fig.9 Cycle Characteristics(LP-433562 )
7.Storage Characteristics
Fig.10 Storage Characteristics(LP-433562)
Fig.11 Recovered capacity ratio at 20 Celsius after storage(LP-433562)
Fig.12 Recovered capacity ratio at 20 Celsius after storage(LP-433562)
Structural Designs
BOKA Lipo battery’s manufacturing process is very simple, mainly the lamination and hot press. By heating in the laminator, the PVDF-HFP polymer in the positive electrode/separator or the negative electrode/separator would fuse together. Besides, the BOKA Lipo battery is using the thermal sealing method, different from laser sealing method of traditional Li-ion batteries, because of the laminate Al film instead of metal cans. The innovation on the manufacturing process lowers the manufacturing cost of Lipo batteries. This would create much greater profit margins.
Fig.1 Structure of BOKA Lipo Battery
Fig.2 Scalabilities of BOKA Lipo Battery
Electrochemical Processes
Fig.3 Key Techniques for BOKA Lipo Battery Production
Electrical & Mechanical Test Methods
1.Electrical Safety Tests
| Items | Condition | Test Method | Specification | Result |
| Short Circuit at 25 ℃ | Fully charged | Connecting the positive and negative terminals of the battery with copper wire having a maximum resistance load of 0.1 Ω. | No explosion or no fire; and the temperature of the battery shall not exceed 150 ℃ | Pass |
| Short Circuit at 60 ℃ | Fully charged | Tests are to be conducted at room temperature and at 58 to 62 ℃ | No explosion or no fire; and the temperature of the battery shall not exceed 150 ℃ | Pass |
| Abnormal Charging | Fully discharged | Cell is initially charged at 3C rate by connecting to a 12V DC-power supply for 48 hours. | No explosion or no fire; and the temperature of the battery shall not exceed 150 ℃ | Pass |
| Over-charging | Fully discharged | The battery is charged at 1CmA to 250% of its rated capacity. | No explosion, no fire, no leakage, or no venting | Pass |
2.Mechanical Safety Tests
| Items | Condition | Test Method | Specification | Result |
| Vibration | Fully charged | Cell is under vibrations of amplitude 0.8 mm, frequency between 10 and 55 Hz., swept at 1Hz./min. for 90min orthogonally in XYZ directions. |
No explosion, no fire, no leakage, or no venting | Pass |
| Shock | Fully charged | Cell is accelerated during the initial 3 msec. with the minimum average acceleration of 75 G, and the peak acceleration between 125 G and 175 G, in XYZ directions. |
No explosion, no fire, no leakage, or no venting | Pass |
| Crush test | Fully charged | Cell is placed between two parallel flat steel plates and the electrodes are parallel to the plates, a force of 13 kN is applied | No explosion or no fire | Pass |
| Impact test | Fully charged | A round rod of 15.8 mm diameter is placed near the center of the cell, parallel to the electrodes and perpendicular to the upper terminal of the cell, and a 9.1 kg weight is dropped from a height of 61 cm to the rod. |
No explosion or no fire | Pass |
| Drop test | Fully charged | Battery is dropped in a free-fall manner for ten times from a height of 1.9m onto a concrete floor, with arbitrary orientation. | No rupture or ignition | Pass |
3.Environmental Safety Tests
| Items | Condition | Test Method | Specification | Result |
| Heating Test | Fully charged | The temperature of the oven is to be raised at a rate of 3 to 7 ℃/min. to a temperature of 148 to 152 ℃ and remain for 10 minutes at this temperature. |
No explosion or no fire | Pass |
| Temperature Cycling | Fully charged | (1)Raise the temperature from 25 to 70 ℃ within 30 min, and then maintain the temperature for 4 hrs. (2)Reduce the temperature from 70 to 25 ℃ within 30 min, and then maintain the temperature for 2 hrs. (3)Reduce the temperature from 25 to -40 ℃ within 30 min, and then maintain the temperature for 4 hrs. (4)Raise the temperature from -40 to 25 ℃ within 30 min, and then maintain the temperature for 2 hrs. (5)Repeat the sequence for further 9 cycles.(6)After 10 cycles, store the cell for 7 days prior to examination. |
No explosion no fire no leakage, or no venting |
Pass |
| Altitude Simulation | Fully charged | Cell is left for 6 hours in an environment with an atmospheric pressure of 11.6 kPa. |
No explosion, fire, leakage, or venting. | Pass |
| High Humidity Storage Performance | Fresh cell | After full charge, store at 60 ℃ and 90%RH for 30 days. | No gassing and no leakage | Pass |
| High Temperature Storage Performance | Fresh cell | (1)After full charge, store at 85 ℃ for 48 hours. (2)After full charge, store at 90 ℃ for 4 hours. |
No gassing and no leakage | Swelling less than 2% |
Major Applications
1.BOKA Lipo batteries possess a rather wide scope of applications. Especially, the trend on nowadays IT products is moving toward the direction of having light-weight, short, and small products. The features of BOKA the Lipo battery is coincident with this trend.
2.Associated application products include MD players, handy recorders, PDAs (personal digital assistants), NBPCs (notebook personal computers), cellular phones, DSCs (digital still cameras), WEs (wireless earphones), and MGPs (mobile game players).
3.Because the thickness of the BOKA Lipo batteries can be very thin that the conventional Li-ion batteries can not accomplish, a lot of applications are developed to make use of Lipo batteries. Those applications include pen computers, pen digital cameras, new style walkman, credit cards, smart cards, other electronic applications and commercial products.
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Precautions for Using BOKA LiPo Battery
1. Charging
1) Charging current
Charging current should be less than maximum charge current specified in the Product Specification. Charging with higher current than recommended value may cause damage to cell electrical, mechanical, and safety performance and could lead to heat generation or leakage.
2) Charging voltage
Charging shall be done by voltage less than that specified in the Product Specification (4.2V/cell). Charging beyond 4.25V, which is the absolute maximum voltage, must be strictly prohibited. The charger shall be designed to comply with this condition.
It is very dangerous that charging with higher voltage than specified value may cause damage to the cell electrical, mechanical safety performance and could lead to heat generation or leakage.
3) Charging temperature
The cell shall be charged within the specified temperature range in the Product Specification.
4) Prohibition of reverse charging
Reverse charging is prohibited. The cell shall be connected correctly. The polarity has to be confirmed before wiring. In case of the cell is connected improperly, the cell cannot be charged. Simultaneously, the reverse charging may cause damaging to the cell which may lead to degradation of cell performance and damage the cell safety, and could cause heat generation or leakage.
2. Discharging
1) Discharging current
The cell shall be discharged at less than the maximum discharge current specified in the Product Specification. High discharging current may reduce the discharging capacity significantly or cause over-heat.
2) Discharging temperature
The cell shall be discharged within the temperature range specified in the Product Specification.
3) Over-discharging
It should be noted that the cell would be at an over-discharged state by its self-discharge characteristics in case the cell is not used for long time. In order to prevent over-discharging, the cell shall be charged periodically to maintain between 3.7V and 3.9V.
Over-discharging may causes loss of cell performance, characteristics, or battery functions.
The charger shall be equipped with a device to prevent further discharging exceeding a cut-off voyage specified in the Product Specification.
Also the charger shall be equipped with a device to control the recharging procedures as follows:
The cell battery pack shall start with a low current (0.01C) for 15 – 30 minutes, i.e. pre-charging, before rapid charging starts. The rapid charging shall be started after the individual cell voltage has been reached above 3V within 15 – 30 minutes that can be determined with the use of an appropriate timer for pre-charging.
In case the individual cell voltage does not rise to 3V within the pre-charging time, then the charger shall have functions to stop further charging and display the cell/pack is at abnormal state.
3. Protection Circuit Module (PCM)
1) The cell/battery pack shall be with a PCM that can protect cell/battery pack properly
PCM shall have functions of (1) overcharging prevention, (2) over-discharging prevention, and (3) over current prevention to maintain safety and prevent significant deterioration of cell performance. The over current can occur by external short circuit
2) Overcharging prohibition
Overcharging prevention function shall stop charging if any one of the cells of the battery pack reaches 4.25V.
3) Over-discharge prohibition
Over-discharging prevention function shall work to minimize a dissipation current to avoid further drop in cell voltage of 2.5V or less per cell in any cell of the battery pack. It is recommended that the dissipation current of PCM shall be minimized to 0.5uA or less with the over-discharge prevention.
The protection function shall monitor each bank of the battery pack and control the current all the time.
4. Storage
The cell should be stored within the proper voltage and temperature range specified in the Product Specification.
5. Handling of Cells
Since the battery is packed in soft package, to ensure its better performance, it’s very important to carefully handle the battery
1) Soft Aluminium foil
The soft aluminum packing foil is very easily damaged by sharp edge parts such as Ni-tabs, pins and needles.
A.Don’t strike battery with any sharp edge parts
B.Trim your nail or wear glove before taking battery
C.Clean worktable to make sure no any sharp particle
2) Sealed edge
Sealing edge is very flimsy.
3) Folding edge
The folding edge is form in battery process and passed all hermetic test
4) Tabs
The battery tabs are not so stubborn especially for aluminum tab.
5) Mechanical shock
Don’t Fall, hit, bend battery body
6) Short
Short terminals of battery is strictly prohibited, it may damage battery.
6. Notice for Designing Battery Pack
1) Pack design
A. Battery pack should have sufficient strength and battery should be protected from mechanical shock
B. No Sharp edge components should be inside the pack containing the battery.
2) PCM design
A. The over-charge threshold voltage should not be exceed 4.32V
B. The over-discharge threshold voltage should not be lower than 2.10V
C. The PCM should have short protection function built inside
7. Notice for Assembling Battery Pack
1) Tab connection
A. Ultrasonic welding or spot welding is recommended to connect battery with PCM or other parts.
B. If apply manual solder method to connect tab with PCM, below notice is very important to ensure battery performance.
a. The solder iron should be temperature controlled and ESD safe.
b. Soldering temperature should not exceed 350?.
c. Soldering time should not be longer than 3s.
d. Soldering times should not exceed 5 times.
e. Keep battery tab cold down before next time soldering.
f. Directly heat cell body is strictly prohibited, Battery may be damaged by heat above approx. 100?
2) Cell fixing
A. The battery should be fixed to the battery pack by its large surface area.
B. No cell movement in the battery pack should be allowed.
8. Others
1) Prevention of short circuit within a battery pack
Enough insulation layers between wiring and the cells shall be used to maintain extra safety protection.
The battery pack shall be structured with no short circuit within the battery pack, which may cause generation of smoke or firing.
2) Prohibition of disassembly
A. Never disassemble the cells
The disassembling may generate internal short circuit in the cell, which may cause gassing, fining, explosion, or other problems.
B. Electrolyte is harmful
LIP battery should not have liquid from electrolyte flowing, but in case the electrolyte come into contact with the skin, or eyes, physicians shall flush the electrolyte immediately with fresh water and medical advice is to be sought.
3) Prohibition of dumping of cells into fire
Never incinerate nor dispose the cells in fire. These may cause explosion of the cells, which is very dangerous and is prohibited.
4) Prohibition of cells immersion into liquid such as water
The cells shall never be soaked with liquids such as water, seawater, drinks such as soft drinks, juices, coffee or others.
5) Battery cells replacement
The battery replacement shall be done only by either cells supplier or device supplier and never be done by the user.
6) Prohibition of use of damaged cells
The cells might be damaged during shipping by shock. If any abnormal features of the cells are found such as damages in a plastic envelop of the cell, deformation of the cell package, smelling of an electrolyte, an electrolyte leakage and others, the cells shall never be used any more.
The Cells with a smell of the electrolyte or a leakage shall be placed away from fire to avoid firing or explosion.
Note:
A.The customer is requested to contact us in advance, if and when the customer needs other applications or operating conditions than those described in this document. Additional experimentation may be required to verify performance and safety under such conditions.
B.We will take no responsibility for any accident when the cell is used under other conditions than those described in this Document.
C.We will inform, in a written form, the customer of improvement(s) regarding proper use and handling of the cell, if it is deemed necessary.