Battery Chemistries

Ni-CD Battery

BOKA Ni-Cd Rechargeable Battery Data Sheets Tables
1.Ni-Cd Cylindrical Battery Data Sheets Table(Standard Type)
2.Ni-Cd High Rate Cylindrical Battery Data Sheets Table(“P” Type).
3.Ni-Cd High Temperature Cylindrical Battery Data Sheets Table(“H” Type).
4.Ni-Cd Low Temperature Cylindrical Battery Data Sheets Table(“L” Type).
5.Ni-Cd Button Rechargeable Battery Data Sheets Table.
6.Ni-Cd 9V Battery Data Sheets Table.

Overview
Rechargeable Ni-Cd batteries are one type of alkaline storage battery, which is classified as secondary battery. Ni-Cd batteries use nickel hydroxide as the positive electrode, cadmium as the negative electrode, and an alkaline electrolyte. They are designated according to the IEC 60285 as alkaline secondary cells and batteries “Sealed nickel-cadmium cylindrical rechargeable single cells”.
First invented by Jungner of Sweden in 1899, the basis for practical application of rechargeable Ni-Cd batteries has been made possible about 50 years later by the development of the totally sealed cell by Neumann of France.
Ever since BOKA development and practical application of rechargeable Ni-Cd batteries, We has continued to make innovations and improvements in order to meet the every increasing needs of the market. As a result, BOKA rechargeable Ni-Cd batteries cover a large area of application market. We has also applied many advanced technological developments in BOKA rechargeable Ni-Cd batteries, including the fabrication of the negative electrode by a pasted method, the fabrication of the positive electrode by a sintered method or by using a new foamed metal material, and the use of a new thin type separator, thus achieving ever-higher levels of reliability and performance.
Giving top priority to meeting the needs of our customers, We will continue to develop new pr-oducts for providing power to the devices that are so important to today’s comfortable, enjoyable, and productive living.

Features
A. Long Service Life and Economical
The cell can provide more than 500 charge/discharge cycles. This makes it extremely economical, and provides an expected life similar to that of the device in which it is used
B. Excellent Discharge Characteristics
BOKA nickel cadmium batteries feature low internal resistance and high, flat voltage characteristics during high current discharge. Compared with conventional models, these products have a higher capacity and charge more rapidly. With the highest energy density of any Ni-Cd battery in the world, they offer unsurpassed discharge characteristics suitable for a wide variety of applications
C. Long Shelf Life
BOKA Ni-Cd cell provides long storage life with few limiting conditions. It offers problem-free charging after long storage, permitting use in a wide range of applications.
D. High Rate Charge
For those applications which require it, the cells can be quick charged or rapid charged in 1-2 hours, using the appropriate charging circuits.
E. Wide Temperature Range
Discharge characteristics are superior, even under low temperature conditions. Cells for high temperature operation exhibit superb charging efficiency and long life, and in some applications can be used above 60 ℃.
F. Reliable, Self-resealing Vent
Each cell is equipped with a self-resealing safety vent, which provides high reliability during long-term use or in the event of charger malfunction.
G. Sealed, Strong, Leak proof Construction
Sealed construction, with no water addition required, provides safety and maintenance-free service. The cell can be used in any desired position during charge, Discharge or storage conditions. Due to the special material used for the gasket, and the use of BOKA original sealing compound, there is no liquid leakage!
H.Wide Application Field
Batteries with capacity from 100-7000mAh are available. BOKA batteries can be used in any cordless equipment.

Electrochemical Processes

Sealed nickel-cadmium cells are electrochemical systems that convert chemical energy into electrical energy in reversible reactions. During charge and discharge the electrochemical processes are represented by the following reactions:
1.Charge/Discharge

2.Overcharge
In a conventional vented nickel-cadmium cell, when approaching full charge, oxygen starts to evolve at the positive electrode, and hydrogen starts to evolve at the negative electrode. This is a side reaction called electrolysis.

Water is lost and has to be replenished. A voltage limitation on charge minimizes the overcharge of a vented cell and then reduces the water consumption.
Sealed cells have a negative electrode with an excess of active material.On charge, the positive electrode will thus first become charged and then will evolve oxygen, before the negative electrode has reached the fully charged state.

The oxygen (1) passes through the porous separator and at the negative electrode reacts with cadmium (2) and water (3) to form cadmium hydroxide (4) discharging the latter electrode at the same rate as it is charged:

Which is the reverse of the reaction at the positive electrode. The negative electrode will therefore never reach the fully charged state, and consequently will not evolve hydrogen. This is called the recombination reaction and makes the sealed nickel-cadmium cell feasible.Which is the reverse of the reaction at the positive electrode. The negative electrode will therefore never reach the fully charged state, and consequently will not evolve hydrogen. This is called the recombination reaction and makes the sealed nickel-cadmium cell feasible.

Structural Designs
1. BOKA Ni-Cd cells are cylindrical, prismatic and button. Using special original manufacturing process, the positive is sintered or foamed, and the negative is pasted or foamed. This unique construction yields high productivity, superior gas absorption, and high capacity and eliminates “memory effect”. BOKA cell consists of positive and negative plates, separator, alkaline electrolyte, metal case, and sealing plate with self-resealing safety vent (Fig. 1 ,Fig. 2 ,Fig. 3,Fig. 4 )

Fig.2 Structure Design of the Button Type CellFig.4 Structure Safety Vent for BOKA Cylindrical Cell

2. The positive plate is a porous, sintered or foamed nickel plate filled with nickel hydroxide. The negative plate is a punched plate of thin steel coated with cadmium active material.
3. The separator is made of nylon or non-waven polypropylene fiber. The positive, separator and negative are sandwiched together and wound into a coil and inserted in the metal case.
4. The electrolyte is an alkaline aqueous solution that is totally absorbed into the plate and separator. The metal case is constructed of nickel-plated SPCC, welded internally to the negative plate. It becomes the negative pole.
5. The sealing plate used a special liquid sealing agent in order to from a perfect seal. The positive is welded internally to the sealing plate, so that it becomes the positive pole. The self-resealing safety vent permits the discharge of an abnormal increase of internal pressure. This prevents the possible danger of rupture or other damage. The vent uses a special alkaline  and oxidation resistant rubber to assure the retention of its operating pressure and safety characteristics over a long period of time.

Charge Characteristics
The current, time, temperature, and other factors affect the charge characteristics of Ni-Cd batteries. Increasing the charge current and lowering the charge temperature causes the battery voltage to rise. Charge generates heat, as a result.
The battery temperature rise. Charge efficiency will also vary according to the current, time, and temperature. For rapid charge, a charge control system is required; refer to the following section on the charge methods for Ni-Cd batteries.
The cell voltage varies with charging current and temperature, but is usually within the range of 1.3V to 1.6V/cell. At the standard charging current(C/10), There is almost no increase in the final voltage at 45 ℃. But at 0 ℃. It can be seen that the voltage may decrease slightly after charging is completed. Although cells can be continuously charged within the range given in the individual data sheets, the following guide is given for longest life:

Charge Type	Rate	Charge Time	Application
Standard Charge	C/10	14-16hrs	All Type
Quick Charge	C/3-C/4	4-6hrs	All Type
Rapid Charge	1-1.5C	1-1.5hrs	All Type
Trickle Charge	C/20-C/30	Continuous	All Type
Minimu	C/30	Continuous	All Type

Fig.5 Standard Charge Characteristics

Fig.6 Temperature Characteristics

Fig.7 Temperature Characteristics

Discharge Characteristics
The discharge characteristics of Ni-Cd batteries will vary according to the current, temperature, and other factors. Generally, in comparison with dry-cell batteries, there is less voltage fluctuation during discharge, and even if the discharge current is high, there is very little drop in capacity. Among the various types of Ni-Cd batteries, there are models such as high-rate type which are specifically designed to meet the need for high-current discharge, such as for power tools, and there are also models such as our new High Capacity type which are designed to meet the need for high capacity, such as for high-tech devices market.

Fig.8 Discharge Characteristics

Fig.9 Effects of temperature in capacity

Fig.10 Capacity V.S high rate discharge

Fig.11 Typical discharge Characteristics(Comparison with Dry-Cell) 

Cycle Life Characteristics
The cycle life of Ni-Cd batteries will vary according to the charge and discharge conditions, the temperature, and other usage conditions. When used in accordance with the IEC charge and discharge specifications, over 500 charge/discharge cycles are possible. The actual cycle life will vary according to which of the various charge formats is used, such as for rapid charge, and also according to how the device powered by the batteries is actually used.

Fig.12 Typical Cycle life Characteristics

Storage Characteristics
There are two major characteristics related to storage life. The first is capacity retention after storage, and the second is charge acceptance after storage. Capacity retention varies widely with ambient temperature, and decrease at higher temperature. When Ni-Cd batteries are stored in a charged state, the capacity will gradually decrease (self-discharge),and this tendency will be markedly great under high temperatures condition. However, the capacity can subsequently recover by charge. Even if the batteries are stored for an extended length of time, but if the storage conditions are appropriate, the capacity will also be restored by subsequent charge and discharge.
Charge acceptance of Ni-Cd cells is affected by the length of storage and storage temperature.The charge acceptance of ours Ni-Cd cells decrease temporarily after long-term storage and/or high-temperature storage conditions, but returns to normal after 1~3 charge/discharge cycles. Actually, there are no problems with charge acceptance of BOKA cell under typical storage conditions. This characteristics widens the applicable use of the ours cell, and is one of the prime reasons why there very few failures during long term storage and subsequent use.

Fig.13 Typical Self-discharge Characteristics

Fig.14 Typical Capacity Recovery After Storage

Safety
If pressure inside the battery rises as a result of improper use, such as overcharge, short-circuit, or reverse charge, a resetable safety valve will function to release the pressure, thus preventing bursting of the battery.

Effects of temperature upon performance
BOKA Ni-Cd cell has excellent discharge characteristics at normal temperature. If the temperature during charge and discharge is high, the capacity tends to decrease. When cells are trickle charged at a high temperature, this tendency is accelerated. Therefore, it is recommended that special high temperature cells be used for application in high temperature ambient.

Fig.15 Temperature Characteristics

Characteristics of each Type
In order to widen the useful application of the BOKA Ni-Cd cell and to use its advantage to the fullest, special purpose types have been developed. Detailed Characteristics of special batteries are shown elsewhere as individual data. Only a summary of characteristics will be given here.
There give special types :
1.Standard type as “S”
2.High Rate Discharge type as “P”
3.High Temperature type as “H”
4.Low Temperature type as “L”
1.Standard Type “S” Type
1) Overview
The standard battery is a combination of high-grade positive and negative plates developed by BOKA own plate manufacturing process. It ensures a high level of electrical capacity and uniform quality among products of the same size. In addition, it features minimized internal resistance and superb discharge performance, displaying stable characteristics over a wide temperature range. Its sealed construction also improves safety and reliability. Furthermore, original special materials are employed for the insulation gasket and liquid sealing guarantees reliable use in high-tech device, the standard battery is available in a wide variety of models and sizes, meeting a broad range of application.
2) Features
A Long Cycle Life
The “S” types battery can be repeated over 500 charge/discharge cycles in cycle service under appreciate condition.
B Free Maintenance
Avoid over-charging or over-discharging it can be easily being handled just like dry cells. Even at discharged state for a long period, the battery is almost free of deterioration of performance.
By simply recharging it after has been stored for a long time at charged or discharged stated, the battery can be reused.
C. Stable in Performance
The battery is not sensitive to heat, and thus can be used in a wide temperature range, because of low internal resistance, stable voltage even after discharge at high current.
3) Application
Gauges, calculators, Portable stereos, portable CD players and other household applications. Printers, portable copy machines, and Word processors, Digital cordless phones, cellular phones, and wireless equipment Cameras, toys, lights, and photographic lights.
4) Characteristics

Fig.16 Typical Charge Characteristics

Fig.17 Discharge Characteristics

Fig.18 Discharge Characteristics

Fig.19 Discharge Characteristics(Vs.Dry Battery)

Fig.20 Typical Self-Discharge Characteristics

Fig.21 Typical Cycle Life Characteristics
Fig.24 Cycle Life Characteristics

2.High Rate Discharge “P” Type
1).Overview
High Rate discharge and Rapid change “P” type batteries were developed through an integration of comprehensive Ni-Cd battery technology combined with the technology for 1.5 hours rapid charge ,improvements in the positive and negative electrode plates and by using the current-collecting system have sharply lowed internal resistance and improve the high rate (5CmA-10CmA) discharge characteristics of because the rise in temperature at the completion of charge has to be controlled ,the voltage and battery temperature during charging should be monitored in order to control the charge current.
2).Features
A.Excellent rapid charge and high-current discharge characteristics
The “P” types batteries can be charged at a current of 1 CmA, thus, making rapid charge in approximately 1 hour possible. It also can be discharged at a high current of 10CmA with about 85% of capacity.
B. Reliable and Stable performance
With conditions of charge at 1CmA and discharge at 10 CmA, The “P” types batteries provide hundreds of charge/discharge cycles, with the very small loss of capacity. Regarding both voltage characteristics and length of use, the performances of “P” types batteries are excellent.
3).Typical Applications
A.Electric tools including drills, screwdrivers and saws
B.Toys, radio-controlled cars
C.Cordless cleaners
D.VCRS
E.Other high rate discharge applications
F.Other general applications
4).Characteristics

Fig.22 Discharge Characteristics
Fig.23 Typical Discharge Characteristics 

3.High Temperature “H” Type
1).Overview
Under the condition of relatively high temperatures where the batteries are continuously charged at low currents to provide power in the event of a power failure (e.g., guide lights, emergency lights), the battery require excellent high temperature trickle charge performance.
By combining a unique negative plate and electrolyte to provide a better high temperature trickle charge performance , specially, for an anti-alkaline non-woven fiber is used as the separator, the “H” type cell can withstand an temperature of 70 ℃ in a short period. Due to special electrolyte, when charge is conducted at a low current of 1/30C to 1/20C in a high temperature ambient, the “H” type cell has improved capacity compared with standard type cell, the cycle life of a cell is influenced by ambient temperature and charge current.
2).Features
A.Long life and high reliability
The high temperature trickle charge “H” type battery is not discharged except during the power supply failure and its life is represented by the period of operation, not cycles. The battery life during trickle charge is affected by the ambient temperature, charge current, discharge frequency and the depth of discharge .Under normal operation, the life is expected to be 5 to 7 years, or even longer.
B. Outstanding performance at High temperature
The “H” type battery has a high trickle-charge efficiency even at a range of temperature as high as 35 ℃ to 70 ℃.
3).Application
A. Emergency lighting
B. Guide lights
4).Characteristics
A.Temperature characteristics
The “H” type battery has out sanding characteristics even in high temperature, As a result of improving its high temperature performance , it has slightly lower discharge capacity at low temperature , however; the “H” type battery can withstand a charge at 0 ℃, and a discharge at -20 ℃, There doesn’t exist any problem in practice.

Fig.25 Trickle Charge Characteristics(compared with the standard type)

B.Charge characteristics
The “H” type battery is usually used at a trickle charge of C/30 to C/20. The charge voltage is slightly higher than that of standard type battery because of improvement of its oxygen generating potential.

Fig.26 Trickle Charge Characteristics

C.Discharge characteristics
The “H” type has same basic structure as the characteristics as standard type battery. It shows improved discharge characteristics when trickle charged in high temperature compared with standard battery.

Fig.27 Typical Discharge Characteristics

D.Service Life
The service life of the “H” type battery is affected by the ambient temperature, charge current, discharge efficiency and depth of discharge though expected over 5 years under normal conditions
High ambient temperature may deteriorate the electrodes or the other cell components, and eventually shorten the life of the battery , In “H” type battery , we used certain appropriate additive to prevent this deterioration .the performance of “H” Type battery is affected very little by a trickle charge current between 1/30C and 1/20C.

Fig.28 Trickle Life Characteristics
Fig.29 Trickle Life Characteristics

4.Low Temperature “L” Type
1).Overview
Under the condition of relatively low temperatures where the batteries are continuously charged at low currents to provide power in the event of a power failure (e.g., guide lights, emergency lights), the battery require excellent low temperature trickle charge performance.
By combining a unique negative plate and electrolyte to provide a better low temperature trickle charge performance , specially, for an anti-alkaline non-woven fiber is used as the separator, the “L” type cell can withstand an temperature of -40 ℃ in a short period. Due to special electrolyte, when charge is conducted at a low current of 1/30C to 1/20C in a low temperature ambient, the “L” type cell has improved capacity compared with standard cell, the cycle life of a cell is influenced by ambient temperature and charge current.
2).Features
A. Long life and high reliability
The high temperature trickle charge “L” type battery is not discharged except during the power supply failure and its life is represented by the period of operation, not cycles. The battery life during trickle charge is affected by the ambient temperature, charge current, discharge frequency and the depth of discharge.
B. Outstanding performance at low temperature

Fig.30 Trickle Charge Characteristics
Fig.31 Trickle Charge Characteristics(compared with the standard type)
Fig.32 Typical Discharge Characteristics

Charge Methods
Charge procedure is the process of returning a discharged state battery to charge state and make it can be reused. If a battery is charged at acurrent that exceeds the allowed maximum value, gas will generate and the internal pressure will increase, if the internal pressure exceeds a specified value, the gas will be released from the safety vent and electrolyte will leak, so electrolyte will decrease and the life of battery will be shorted. To select some appropriate charge methods are necessary to make full use of a battery.

Charge Method	Cycle(Repeated) Use
	Quasi-constant-current charge	Timer-control charge	-AV cut off charge	Temperature cut off charge	Trickle charge
Oprations V=Batter voltage I=Charge current T=Batter temperature
Features	.Simple and economical charge method widly used for long charge time with low charge current	.Simple and economica .More reliable charge with additional charge time	.The extra safety and reliable typical charge control system .Very good battery protection	.Economical and safety charge method .Reliable to overcharge at low tempetature and end charge at high tempetature	.Simple and economical charge method used for continuous long charge
No. of output terminals	2	2	2	2
Charge time	15 hours	6 to 8 hours	1 to 2 hours	1 to 2 hours	30 hours or longer
Charge current	0.1 CmA	0.2 CmA	0.5 to 1 CmA	0.5 to 1 CmA	Frequent charge 1/20 to 1/30Cma
Charge level at charge control		Approx. 120%	Approx. 100 to 20%	Approx.110 to 150%
“S” type	Most recommended	Acceptable	—-	—-	—-
“P” type	Acceptable	Acceptable	Most recommended	Most recommended	—-
“H” type	—-	—-	—-	—-	Most recommended
“L” type	—-	—-	—-	—-	Most recommended
Application examples	.Cordless Phone .Shaver	.R/C Toy .Wireless equipment	.Celluar Phones .High-Tech Erectric Products	.Portable Power .Racing Toy	.Emergency Lighting .Timer

Fig.33 General Comparison of the Various Charge Systems 

There are lots of methods to charge secondary batteries, such as constant current (CC) charge, trickle charge, and fast charge. In selecting the most suitable one, the frequency of use, the discharge rate, and the application of its use, should be considered. The methods are discussed in the following paragraphs.
1.Constant Current Charge
Charging efficiency is high when a cell is charged with continuous constant current. The necessary charge input is easily determined by the charge time, and the number of cells may be changed, with a constant current simultaneously within a range of the output voltage of the power supply, However, the constant current needed for DC power supply is costly, so quasi-constant current is generally used in charging.

Fig.34 Constant Current charge Circuit

2.Quasi-Constant Current Charge
In this method, the constant current is produced by inserting resistance between the DC power supply and the cell in series, so as to increase the impedance of the charging circuit. The value of the resistance is adjusted according to the charge current at the end of charging, which should not exceed the specified current value. Quasi-constant current is widely used in charging the Ni-Cd batteries because the circuit configuration is simple, and less expensive. An example of this circuit plan is illustrated in Fig.35. As to the equipment having both AC and DC circuits, additional charger is not necessary. The DC circuit in the equipment can charge the battery.

Fig.35 Quasi-Constant Current charge Circuit
Fig.36 Charge Characteristics of the Quasi-constant-current Charge System

3.Constant Voltage Charge
When charging a Ni-Cd battery, using the potential difference between the power supply and the cell voltage regulates the charge current. In this method the charge current becomes high during the initial charging period, and becomes low at the end of charging. It varies in response to fluctuations in the power supply voltage, so that the charge current should be set to reach the maximum permissible input rate when the power supply voltage is at its highest. Also, with this method, since cell voltage decreases after reaching its peak at the end of charging, the charge current increases. This in turn leads to a rise in the cell temperature. Furthermore, as the cell temperature increases, the voltage decreases further. This may lead to a phenomenon so called thermal runaway at the end of charging and damage the battery s performance. For this reason, constant voltage charging is not recommended for Ni-Cd batteries.

Fig.37 Constant Voltage charging Circuit

4.Trickle Charge
In trickle charge, the battery is continuously charged at a very low rate, from C/30 to C/20, and is kept fully charged and ready for use. Trickle charge is applied to Ni-Cd batteries used in fire alarms and emergency lighting. Fig.38 is an example of trickle charge circuit.

Fig.38 Trickle charging Circuit

5.Floating Charge
The Ni-Cd batteries are connected by the circuit to a charging power supply with a load in parallel. Normally, power flows from the DC source to the load, and when the load increases to a maximum, or when power stops being supplied by the source, power will be discharged from the cell. In this system, charge current is determined by the pattern of use, namely, thefrequency of discharge and the discharge rate. This method is mainly used in emergency power supply, memory backup, or for electric clocks, where no power cut is allowed. Fig.34 illustrates the block diagram for floating charge where the resistance should be adjusted so the current will be equal to the specified rate.

Fig.39 Floating Charge Block Diagram

6.Step Charge
In step charge, the initial charge current is kept relatively high. As the state of full charge is determined by measuring the battery`s charge voltage, the circuit is switched to trickle charge, such as, from 0.2C to 0.02C.
This is the most ideal method of charging, the disadvantages being the complicated circuitry and resulting in high cost. There are also some existing problems in detecting the end of charge at the high rate. Fig.40 illustrates the pattern of step charge.

Fig.40 Step Charge Block Diagram

7.Charging via Solar Cells
This is the most simple charge circuit. Use the reverse-flow prevention diode with a small voltage drop in order to achieve high charging efficiency. Outdoors, temperature variations are apt to be wider, so it is recommended that charge circuits utilizing solar cells are designed so that temperature variations do not exceed the predetermined temperature range.

  Fig.41 Charge Circuit Using Solar Cells

The output current of solar cells is affected by weather conditions. Fig.42 shows how the output current of a solar cell relates to the time of the day. When cloudy, charge input is insufficient. However, solar cells must be designed so that maximum output current in sunny weather will not exceed the specified current.

 Fig.42 Solar Cell Output Current

8.Quick Charge
For charging in a short time with a high current, an external control circuit is necessary. This method detects cell voltages and cell temperatures at the end of the charging cycle and stops charging. Fig.43 shows the block diagram for this method.

1)Cell Voltage Detection
Cell voltage is detected near the end of high-rate charge to active the controller and divert charging current to low-rate current through the bypass circuit.
In this system, a compensation circuit is required to cope with the charge voltage fluctuation due to charge current, ambient temperature, etc.,
Since the cut-off voltage (Vc) must be predetermined lower than the peak value of the charge voltage, auxiliary charge at a low current level is often combined in order to secure charge capacity.

2) -AV Detection Control System
Under this system, the charge current is controlled by detecting the decrease (-AV) in the cell voltage at the end of charging. Fig.43 shows an outline of the -AV detection control system.
The method employs a voltage detection system. However, an ambient temperature compensation circuit is not required as the cell voltage peak value is stored, and based on this value, the charge current is cut off when a certain voltage reduction level is reached.

  Fig.43 -AV Detection Control System

3) Cell Temperature Detection
At the end of charge, cell temperature shows a rise due to heat generated by the recombination of oxygen gas on the negative electrode. It is feasible to detect this temperature change by setting a sensor such as a thermister or a thermostat on the exterior of the cell casing for the purpose of charge current control. Under this method, current is controlled in the overcharge range, which means that exclusive batteries with superior overcharge characteristics must be employed. Fig.44 shows outline. Here the cell itself should be suitable for temperature detection. The control system is simple and less expensive.

 Fig.44 Cell Temperature Detection System

4) Timer Control
Charging is performed over a certain length of time specified in advance by a timer, so that charge input is nearly constant. This method is adequate in charging a cell with no residual capacity, but may cause overcharging a cell with some residual capacity. Therefore, the charging condition should be carefully selected.

9.Designing Charging Circuits
The power supply and the detector are the most crucial parts in the design of a charging circuit for ordinary and quick charge units. Charging current usually fluctuates with changes in input voltage and frequency. Accordingly, charging circuits must be designed on a basis of the maximum AC input voltage, 110% of the rated value.

1) Rectification Methods
The number of Nickel-Cadmium sealed cells built into battery-powered devices, and space for a transformer, should be taken into account when selecting an appropriate current rectifying method-a single-phase half-wave, or single-phase full-wave circuit. Table compares respective rectification methods.

2) Selection of Transformers
Charging circuits are normally provided with a small built-in transformer which steps down and rectifies voltage. Charging is performed by virtue of a difference in the potential between the secondary voltage of the transformer and the cell voltage. The charging current is monitored by placing a fully charged cell into the circuit as a load.

3) Compact and Lightweight Transformer
Greater charge current requires a transformer with larger capacity, which is naturally larger in size as well. A transducer is often required, due to the restrictions of space and weight, where the transformer is part of the circuit. The switching regulator type is widely used for this purpose. Since in a switching regulator transformer, the frequencies are converted into several tens or hundreds of KHz, great care should be taken with regard to internally generated noise.

4) Designing The Detection Circuit
There are various detection circuits in use, as described in above chaper. Their design must be based on a thorough knowledge of the cell characteristics.
The following cell characteristics may affect the setting of the detection level:

For voltage detection:
(1) Charge current
(2) Ambient temperature
(3) Battery history

For temperature detection:
(1) Charge current
(2) Ambient temperature
(3) Assembled battery configuration
(4) Ventilation

Should any question arise concerning battery characteristics when designing a detection circuit, please contact BOKA.

10.Parallel Charge and Parallel Discharge
When charged in parallel, the difference in charger voltage among the Ni-Cd batteries causes larger current flow into the cell with less charge voltage. The charge voltage of the Ni-Cd battery reaches its peak near the end of charging, then decreases after being fully charged, so the charge current increases to infinity and ultimately destroys the battery. Thus, parallel charging should be avoided. When parallel charging is unavoidable, due to the structural arrangement of the device, parallel charging with diodes in the circuit may be used as shown in Fig.45.

  Fig.45 Parallel Charge Circuit

The slight difference in cell voltage in the Ni-Cd batteries may cause no particular problem by parallel discharging. When a battery which has abnormally low voltage is used, caused by a short or some other deviation, the high current which flows into the battery may generate heat, burn the lead wire and eventually damage the device in which it is being used. To avoid this situation the circuit is adopted as shown in Fig.46.

Fig.46 Parallel Discharge Circuit

Battery Pack Design
BOKA Ni-Cd cells are versatile performers easily adapted to most application demands. Economical off-the-shelf designs can be tailored to the specific voltage, space, and termination requirements of an application.
Figure 26 illustrates a typical battery installation within a representative application, while Figure 27 diagrams many of the components recommended for a Ni-Cd battery.

Figure 26.Installation Within Typical Application

1. Packaging Considerations
Ni-Cd batteries are generally packaged in two forms:
Hard plastic cases are recommended for applications requiring the end-user to handle the battery. These cases offer greater protection against handling damage and shock and vibrations stresses. But depending on the design, thermal management may be more difficult within the hard case. Injection molding of hard.

Figure 27.Elements of Battery Assembly

cases requires a substantial investment for mold construction and is thus best suited for high volumes.
Lighter shrink-wrapped plastic packaging may be used when routine battery removal is not expected. These packs, as illustrated in Figure 27, usually consist of the cell assembly with insulators covering the exposed terminals. Plastic shrink tubing then covers the whole pack. Shrink-wrapped batteries have acceptable mechanical integrity for assembly, and when properly secured, withstand normal portable-product shock and vibration levels. Shrink packaging provides ample opportunity for hydrogen to diffuse and for internally generated heat to dissipate. Additional insulation from heat my be needed at the tangent points within the cell stacks (where they shrink material directly contacts the cell).
Either type of packaging must maintain adequate ventilation to the individual cells while providing room for cell interconnections, battery terminations, and requisite charge control sensors.
2. Shape
Battery shapes can be adjusted to fit application constraints. Among the most popular battery shapes are the following:
1) Sticks—the terminal of one cells butts against the base of the next cell forming a long, slender battery.
2) Linear—the cells are placed side by side in a straight line.
3) Paired—cells are arranged in two(or more)symmetric rows.
4) Nested—the cells of one row are nested within the indentations formed by the adjacent row.
3. Materials
Materials used in the assembly of Ni-Cd batteries must withstand the high temperature environment that accompanies venting of the cell. Because of the exothermic nature of the charging process, should cells vent in overcharge, the vented gases will be largely high-temperature hydrogen[>200 ℃]. Although these gases will quickly disperse and cool, all materials used in cell construction must be capable of withstanding elevated temperatures while remaining inert in a hydrogen environment. Recommended materials for use in Ni-Cd battery construction include those below. Consult with BOKA regarding specific material specification details.
1) Wires
To connect the batteries to the device, the vinyl-clad electrical wire for heat-resistant device wiring cinforming to UL-1007 is generally used. Red for the positiveside and black for the negative side are the standard colors. The ends of the lead wires may be bare cut ends or connected to connectors, etc.
All wire insulation should be Teflon® , Kapton® , or other material with a minimum temperature rating of 200 ℃.

Standard Lead wire.

Applicable Battery Size	Lead Wire
	Size	Length(mm)	Color
AAA Size	UL1007 AWG 24	Approx.200	+Red – Black
AA Size	UL1007 AWG 24	Approx.200
A Size	UL1007 AWG 22	Approx.200
SC Size	UL1007 AWG 18/UL1015 AWG 18	Approx.200
C Size	UL1007 AWG 20/UL1015 AWG 18	Approx.300
D Size	UL1007 AWG 18/UL1015 AWG 18	Approx.300

2) Sleeving
Shrink sleeving made of polyvinyl chloride are used on many packs as the external cover.Tube thickness ranges from 0.1mm to 0.2mm depending on battery type and configuration. All shrink sleeving should be able to withstand 200 ℃. PVC sleeving is not generally recommended. Kraft paper or fishpaper sleeving should be approximately 0.007 inches thick.
3) Insulation
All cell insulation should be able to withstand 105 ℃ for 24 hours. Vent shields must be constructed of Nomex® or other insulating material capable of withstanding 210 ℃.
4) Case Material
Plastic cases must meet UL 9V40. Case materials without a rating of 210 ℃ DTUL(Deflection Temperature Under Load)must be provided with vent shields over the positive ends of the cells.
4. Interconnections and Terminations
Cell interconnections typically consist of nickel(Ni200)strip or nickel-plated steel ribbon spot-welded from one cell terminal to the adjacent cell’s case. Nickel bus strips offer good solder ability, that can be securely spot-welded to the cells, and that is highly electro conduvtive, and alkaline-resistant. Minimum recommended nickel strip size is 0.187 inches wide by 0.005 inches thick. Wire interconnections are rarely used because of the difficulty in attachment since soldering directly to cells is forbidden.
Battery terminations come in a variety of configurations ranging from simple flying leads(wires soldered to weld lugs which are then welded to the cells)in permanent installations to much more elaborate contact or connector systems on removable battery packs. Removable battery packs should be designed with a connection system that produces a minimum of 2 pounds of force while incorporating a wiping action on insertion to cut through oxide layers on the connection surfaces.
Recommended Terminal Plate Dimensions (Material:Nickle)

Dimensions(mm)	Applicable Battery Size	Internal Impedance	Configuration
L×W×T
13×3×0.12	AAA Size	2.5Ω
19×3×0.12	AA,A Size	4.0Ω
25×5×0.15	SC Size	2.5Ω
27×6×0.2	SC Size	2.0Ω
30×6×0.2	D Size	2.0Ω
13×5×0.2	SC,C,D Size	1.0Ω

5. Other Components
1) PTC Resistor
Positive temperature coefficient resistors such as Raychem’s PolySwitch® circuit protector provide a latching, but resettable device for protection against short-circuit conditions.
2) Thermostat
Thermostats or other resettable thermal control devices are typically used for backup to the primary charge control system to guard against extended overcharge and the resulting elevated temperatures.
3) Thermal Fuse
Thermal fuses that open at a suitably elevated temperature(nominally 90 ℃)are often used as a third tier of thermal protection(after the normal charge control system and thermostat). They are a fail-safe measure since the battery charging system will become inoperative.
4) Thermistor
Thermistors are normally used for the temperature-sensing necessary for recommended charge control schemes.
6. Standard Configurations
A wide variety of standard battery configurations have been developed by cell manufacturers encompassing permutations of cell size/capacity, voltage, terminations, and charge control and termination sensors.
As a minimum,We recommends that the following be included in any standard battery design:
1) Primary Charge Control System—The standard temperature or time-based charge control system to switch to maintenance charging
2) Backup Resettable Thermal Protection—Terminates charging if the primary control system should fail to switch prior to extended overcharge. Normally set to 70 ℃.
3) Fail-Safe Thermal Fuse—Permanently opens charge circuit if battery temperature exceeds acceptable limits. Normally set to 90 ℃.
4) Short-Circuit Protection—Provides protection in cases of excess discharge current.
5) Vents and Vent Shielding—Gas management system to diffuse and cool a vented stream of hydrogen.
7. Location
Ni-Cd cells are most commonly used in battery packs. In using Ni-Cd batteries, the type of battery, the number of cells, the shape of the battery pack, and the components of the battery pack will be determined by the rates (voltage and current )of the device, the charging specifications, the amount of space available inside the device, and the usage conditions.
While battery location is generally influenced by product design constraints such as available space, influence on center of gravity, and ease of access, battery locations should also provide adequate ventilation, isolation from ignition sources and separation from major heat generators.
After consultation concerning specifications, if so desired, we can also provide assembly services for battery packs.

Battery Pack Configurations Designation System

1.Designation System For Battery Packs
The designation of a battery pack is composed of 7 sections each of them are used to identify different information:

XX-X-ABCDEFG HIJK M N PQ

XX——————Shenzhen DGT Technology Development Co.,Ltd.
X——————–Chemical System. H–Nickel/Metal Hydride Battery.D–Nickel/Cadmium Battery.L–Li-ion Battery.LP–Li-ion PolymerBattery.
ABCDEFG——–Size of Cell
HIJK—————-Capacity
M——————-Number of Cells in a Pack
N——————-Configuration Code
PQ——————Tag or Connector Type Code

2.Standard Configurations For Battery Packs
The following are the standard pack configurations for Ni-Cd batteries. Refer to these configurations when designing the battery pack.
A Type
The repuired number of single cells are stacked in a vertcial column and connected by nickel plates, and covered with an external heat-shrink PVC tube.
B Type
The repuired number of single cells are arranged in a row and connected by nickel plates, and covered with an external heat-shrink PVC tube.
G Type
The repuired number of single cells are stacked in two vertical columns of inequality numbers cells and connected by nickel plates, and covered with an external heat-shrink PVC tube.
S Type
The repuired number of single cells are stacked in multiple columns ared layers and connected by nickel plates, and covered with an external heat-shrink PVC tube.
T Type
The repuired number of single cells are arranged in a horizontal triangle and connected by nickel plates, and covered with an external heat-shrink PVC tube.
W Type
The repuired number of single cells are arranged in horizontal triangle rows in one or more layers and connected by nickel plates, and covered with an external heat-shrink PVC tube.
Y Type
The repuired number of single cells are arranged in more horizontal rows and connected by nickel plates, and covered with an external heat-shrink PVC tube.

3.Tag Type Specifications

4.Tag Direction Codes

5.Connector Type Specifications

Major Applications
The Ni-Cd batteries are available for wide application by taking advantage of the features:compact, easy handing, long shelf life,and high energy density.
1.For Cyclic Use
A.Consumer Applications
Shavers, portable VTRc(VCRs), radios, televisions, tape recorders, portable computers.
B.Communication and Telephone equipment
Cordless and portable telephone, transceivers, pocket pagers, car telephone systems.
C.Office Equipment
Portable calculators, electronic cash registers, printers, and typewriters.
D.Cordless Tools
Grass and hedge trimmers, cordless drills, screwdrivers, hammer drills, saws.
E.Instruments and Medical equipment
Electronic instruments, measuring equipment, medical electronics, heart defibrillators.
F.Photography
Electronic cameras, strobe, VTR and movie lights.
G.Toys and Hobby
Radio-controllers, model motor driving, lights.
2. For Trickle or Float Charge Use
A.Emergency Devices
Lights, fire and burglar alarms, communication system, fire shutters.
B.Memory Backup
Electronic cash registers, computers, sequencers, memory chips.

Precautions  for Using Ni-Cd Cell or Batteries
In order to take full advantage of the properties of Ni-Cd batteries`characteristics in use and in the design of battery-operated, and also to prevent problems due to improper use, please pay proper attention to the following points .
1. Charging
1) Charging Temperature
A.Charge batteries within an ambient temperature range of 0 ℃ to 45 ℃.
B.Ambient temperature during charging affects charging efficiency. As charging efficiency is best within a temperature range of 10 ℃ to 30 ℃, whenever possible place the charger (battery pack) in a location within this temperature range.
C. At temperatures below 0 ℃ the gas absorption reaction is not adequate, causing gas pressure inside the battery to rise, which can activate the safety vent and lead to leakage of alkaline gas and deterioration in battery performance.
D. Charging efficiency drops at temperatures above 40 ℃. This can disturb full charging and lead to deterioration in performance and battery leakage.
2) Parallel charging of batteries
Sufficient care must be taken during the design of the charger when charging batteries connected in parallel. Consult BOKA when parallel charging is required.
3) Reverse charging(Never reverse charge!!!)
Charging with polarity reversed can cause a reversal in battery polarity, causing gas pressure inside the battery to rise, which can activate the safety vent and lead to alkaline electrolyte leakage, rapid deterioration in battery performance, battery swelling or battery rupture.
4) Overcharging(Avoid overcharging!)
Repeated overcharging can lead to deterioration in battery performance.
(“Overcharging” means charging a battery when it is already fully charged.)
5) Rapid charging
To charge batteries rapidly, use the specified charger (or charging method recommended by us) and follow the correct procedures.
6) Trickle charging (continuous charging)
Carry out trickle charge by applying the current of 1/30 to 1/20 CmA. The correct current value is determined depending on the features and purpose of the equipment.
Note : “CmA” During charging and discharging, CmA is a value indicating current and expressed as a multiple of nominal capacity. Substitute “C” with the battery’s nominal capacity when calculating. For example, for a l500mAh battery of 0.033CmA, this value is equal to 1/30×1500, or roughly 50mA.
2. Discharging
1) Discharge Temperature
A. Discharge batteries within an ambient temperature range of -20 ℃ to +65 ℃.
B. Discharge current level affects discharging efficiency. Discharging efficiency is good within a current range of 0.1 CmA to 0.5 CmA.
C. Discharge capacity drops at temperatures below -20 ℃ or above +65 ℃. Such decreases in discharge capacity can lead to deterioration in battery performance.
2) Overdischarge (Deep Discharge)
Since overdischarging (deep discharge) damages the battery characteristics, do not forget to turn off the switch when discharging, and do not leave the battery connected to the equipment for a prolonged periods.Besides, avoid shipping the battery installed in the equipment.
3) High Current Discharging
As high current discharging can generate a lot of heat and decreased discharging efficiency, please consult us before attempting continuous discharging or pulse discharging at currents larger than 2 CmA.
3. Storage
1) Short-term Storage temperature and humidity
A. Store batteries in a dry location with low humidity, no corrosive gases, and at a temperature range of -20℃ to +45℃.
B. Storing batteries in a location where humidity is extremely high or where temperatures fall below -20℃ or rise above +45℃ can lead to the rusting of metallic parts and battery leakage due to expansion or contraction in parts composed of organic materials.
2) Long-term storage (2 year, -20℃ to +35℃)
A. Because long-term storage can accelerate battery self-discharge and lead to the deactivation of reactants, locations where the temperature ranges between +10℃ and +30℃ are suitable for long-term storage.
B. When charging for the first time after long-term storage, deactivation of reactants may lead to increased battery voltage and decreased battery capacity. Restore such batteries to original performance by repeating several cycles of charging and discharging.
C. When storing batteries for more than 1 year, charge at least once a year to prevent leakage and deterioration in performance due to self-discharging. When using a rapid charge if voltage detection type, carry out charge and discharge at least once every 6 months.
4. Service Life of Batteries
1) Cycle life
Batteries used under proper conditions of charging and discharging can be used 500 cycles or more. Significantly reduced service time in spite of proper charging means that the life of the battery has been exceeded. Also, at the end of service life, an unusal increase in internal resistance, or an internal short-circuit failure may occur. Chargers and charging circuits should therefore be designed to ensure safety in the event of heat generated upon battery failure at the end of service life.
2) Service life with long-term use
Because batteries are chemical products involving internal chemical reactions, performance deteriorates not only with use but also during prolonged storage. Normally, a battery will last 3 to 5 years (or 500 cycles) if used under proper conditions and not overcharged or overdischarged. However, failure to satisfy conditions concerning charging, discharging, temperature and other factors during actual use can lead to shortened life (or cycle life) damage to products and deterioration in performance due to leakage and shortened service life.
5. Design of Products Which Use Batteries
1) Connecting batteries and products
A.Never solder a lead wire and other connecting materials directly to the battery, as doing so will damage the battery’s internal safety vent, separator, and other parts made of organic materials.
B.To connect a battery to a product, spot-weld a tab made of nickel or nickel-plated steel to the battery’s terminal strip, then solder a lead wire to the tab. Perform soldering in as short a time as possible.
C.Use caution in applying pressure to the terminals in cases where the battery pack can be separated from the equipment.
D.When rapid charging using the voltage detection method with a large current (1C or more), or when eaving the battery installed in the equipment, be sure to follow connecting the precaution listed above. Even for other uses, if connecting the precaution listed above is used as much as possible, contact defects in the connection process can be reduced.
2) Material for terminals in products using the batteries
Because small amounts of alkaline electrolyte can leak from the battery seal during extended use or when the safety vent is activated during improper use, a highly alkaline-resistant material should be used for a product’s contact terminals in order to avoid problems due to corrosion.

High Alkaline-resistant Metals	Low Alkaline-resistant Metals
Nickel stainless steel, nickel plated steel, etc	Tin ,aluminum, zinc, cooper, brass,etc

(Note: That stainless steel generally results in higher contact resistance.)
3) Temperature related the position of batteries in products
As excessively high temperatures (i.e. more than 45℃) can cause alkaline electrolyte to leak out from the battery, thus damaging the product and shorten battery life by causing deterioration in the separator or other battery parts, install batteries far from heat-generating parts of the product. The best battery position is in a battery compartment that is composed of an alkaline-resistant material which isolates the batteries from the product’s circuitry. This prevents damage that may be caused by a slight leakage of alkaline electrolyte from the battery. Be careful particularly when trickle charge is carried out(for contions charge).
4) Discharge end voltage
Overdischarge and reverse charge of the battery deteriorate battery characteristics. This can be caused by several actions, such as forgetting to turn off the power. Installing an overdischarge cutoff circuit is recommended in order to avoid overdischarge and reverse charge.
The discharge end voltage is determined by the formula given below. Please set the end voltage of each battery at 1.1 volts or less.
Number of batterries arranged serially:

1 to 6	(Number of batteries×1.0)V
7 to 20	[(Number of batteries-1)×1.2]V

5) Overdischarge (deep discharge) prevention
Overdischarging (deep discharging) or reverse charging damages the battery characteristics. In order to prevent damage associated with forgetting to turn off the switch or leaving the battery in the equipment for extended periods, it is hoped that preventative options should be incorporated in the equipment. At the same time, it is recommended that leak-age current is minimized. Besides, the battery should not be shipped inside the equipment.
6. Prohibited Items Regarding the Battery Handling
We assumes no responsibility for problems resulting from batteries handled in the following manner.
1) Disassembly
Never disassemble a battery, as the electrolyte inside is strong alkaline and can damage skin and clothes.
2) Short-circuiting
Never attempt to short-circuit a battery. Doing so can damage the product and generate heat that can cause burns.
3) Throwing batteries into a fire or water
Disposing of a battery in fire can cause the battery to rupture. Also avoid placing batteries in water, as this causes batteries to cease to function.
4) Soldering
Never solder anything directly to a battery. This can destroy the safety features of the battery by damaging the safety vent inside the cap.
5) Inserting the batteries with their polarities reversed
Never insert a battery with the positive and negative poles reversed. as this can cause the battery to swell or rupture.
6) Overcharging at high currents and reverse charging
A. Never reverse charge or overcharge with high currents (i.e. more than rated). Doing so causes rapid gas generation and increased gas pressure, thus causing batteries to swell or rupture.
B. Charging with an unspecified charger or specified charger that has been modified can cause batteries to swell or rupture. Be sure to indicate this safety warning clearly in all operating instructions as a handling restriction for ensuring safety.
7) Installation in equipment (with a sealed construction)
Always avoid designing airtight battery compartments. In some cases, gases (oxygen, hydrogen) may be given off, and there is a danger of the batteries bursting or rupturing in the presence of a source of ignition(sparks generated by a motor switch, etc.).
8) Use of batteries for other purposes
Do not use a battery in an appliance or purpose for which it was not intended. Differences in specifications can damage the battery or appliance.
9)Short-circuiting of battery packs
Special caution is required to prevent short-circuits.Because of product or battery shape, in case battery packs that are used as insertion to equipment may be inserted in reverse. And also, caution must be given to certain structures, which, depending on product terminal shape, for instance, can make short-circuiting more likely.
10) Using old and new batteries together
Avoid using old and new batteries together. Also avoid using these batteries with ordinary dry-cell batteries, Ni-Cd batteries or with another manufacturer’s batteries. Differences in various characteristic values, etc.,can cause damage to batteries or the product.
7. Other Precautions
A.Batteries should always be charged prior to use. Be sure to charge correctly.
B.In order to ensure safe battery use and to prolong the battery performance, please consult us regarding charge and discharge conditions for use and product design prior to the release of a battery-operated product.
C.A rechargeable battery is delivered without charge, so its voltage may be lower than 1.2V. It will recover to normal level after a charge cycle.
D.Before the test or use, batteries shall be discharged because they may have some residual capacity.
E.Do not swallow batteries.