Battery Chemistries-Ni-MH Battery

Battery Chemistries

Ni-MH Battery

BOKA Ni-MH Rechargeable Battery Data Sheets Tables
1.Ni-MH Cylindrical Battery Data Sheets Table(Standard Type)
2.Ni-MH Cylindrical Battery Data Sheets Table(Consumer Type).
3.Ni-MH Prismatic Battery Data Sheets Table.
4.Ni-MH Button Battery Data Sheets Table.
5.Ni-MH 9V Battery Data Sheets Table.

Overview
Mobility is increasingly viewed as an essential attribute of today’s lifestyles, both personal and professional. Advanced electronic devices such as cellular phones and portable computers now permit people on the go to operate more effectively than was possible in home and office-bound environments of a generation ago. But the price of mobility have been increasing demands and dependence on portable power sources.
Fortunately, with the development of new nickel-metal hydride(Ni-MH)battery options, improvements in electronics have now been matched by significant improvements in the batteries that power them. Nickel-metal hydride battery cells provide more power(in equivalently sized packages)than nickel-cadmium(Ni-Cd)cells while also eliminating some of the concerns over use of heavy metals in the cells.

Features
1.Green Power
BOKA Ni-MH batteries are free of cadmium and mercury. They are an environmental friendly chemical power source.
2.Similarity with Ni-Cd Battery
BOKA Ni-MH batteries has almost same discharge characteristics as those of Ni-Cd batteries.
3.Double Energy Density of Conventional Batteries
BOKA Ni-MH batteries have approximately double capacity compared with standard Ni-MH batteries.
4.Cycle Life Equivalent to 500Charge and Discharge Cycles
Like Ni-Cd batteries, BOKA Ni-MH batteries can be repeatedly charge and discharge for about 500 cycles(IEC 61436 charge and discharge conditions).

5.Rapid charge in approx. 1.2 hours
BOKA Ni-MH batteries can be rapidly charge in about an hour by using a specially designed charger.

6.Excellent discharge characteristics
Since the internal resistance of BOKA Ni-MH batteries is low, high-rate discharge up to 3CmA is possible.

Designing for BOKA Nickel-Metal Hydride Cells

Incorporation of nickel-metal hydride cells into applications is generally straightforward, particularly for designers accustomed to designing with nickel-cadmium cells. Primary differences between the two cell chemistries are:
1)Nickel-metal hydride cells offer higher energy densities.
2)Environmental and occupational health issues relating to cadmium are eliminated with nickel-metal hydride cells.
3)More care is required in design of nickel-metal hydride charging systems.
4)Since nickel-metal hydride cells may emit hydrogen in heavy overcharge or overdischarge, both charge-control redundancy and location of the battery package in the product deserve careful scrutiny.
5)Nickel-metal hydride cells have yet to offer the wealth of sizes and design variations found in the mature nickel-cadmium line.

1.Capacity Guide
A convenient aid to early analysis of battery systems is the cell selection guide shown in Figure 25. This chart allows estimation of the run times available from specified cell sizes when exposed to a given constant discharge rate.

Figure 25.Nickel-Metal Hydride Cell Selection Guide

Included on the chart are nickel-metal hydride cell sizes available from the manufacturer at the publication date. Other sizes are being added rapidly; consult the manufacturer for an updated capacity guide covering existing offerings. Note that comparison information is also provided for one size of nickel-cadmium cell to allow estimation of the actual performance increment achieved with nickel-metal hydride cells.
Typical use for the capacity guide is to enter the guide with a given discharge rate. The intersection of that discharge rate with the performance line for each cell size then indicates the amount of run time nominally available from that cell. The values provided by this guide should be used for planning purposes only; final cell selection should be based on actual discharge times obtained from testing under realistic application scenarios.

2.Materials of Construction
The materials of construction for the nickel-metal hydride cell external surfaces are, like the nickel-cadmium cell, largely comprised of nickel-plated steel, and therefore, are resistant to attack by most environmental agents.

3.Orientation
Nickel-metal hydride cells will operate satisfactorily in any orientation.

4.Environmental Suitability
The nickel-metal hydride cell is designed to operate effectively in all environments normally experienced by portable electronic equipment. Application designers intending to use nickel-metal hydride cells in especially adverse environments should consult closely with the cell manufacturer to ensure design suitability.

5.Temperature
Like most other battery cells, nickel-metal hydride cells are most comfortably applied in a near-room-temperature environment(-25℃); however, with careful attention to design parameters, they can be successfully utilized when exposed to a much wider range of temperatures.
1)Operating
Nickel-metal hydride cells can be successfully applies in temperatures from 0 to 50℃ with appropriate derating of capacity at both the high and low ends of the range. Design charging systems to return capacity in high or low temperature environments without damaging overcharge requires special attention.
2)Storage
Cells are best stored in temperatures from 0 to 30℃ although storage for limited periods of time at higher temperatures is feasible.

6.Shock and Vibration
Expect nickel-metal hydride cells to easily withstand the normal shock and vibration loads experienced by portable electronic equipment in day-to-day handling and shipping. Consult with BOKA regarding applications required operation in more intense shock and vibration environments.

7.Ventilation and Isolation
The primary gas emitted from the nickel-metal hydride cell when subjected to excessive overcharge is hydrogen as opposed to oxygen for the nickel-cadmium cell. Although venting of gas to the outside environment should not occur in a properly designed application, isolation of the battery compartment from other electronics(especially mechanical switches that might generate sparks)and provision of adequate ventilation to the compartment are required to eliminate concerns regarding possible hydrogen ignition.
Isolation of the battery from heat-generating componetry and ventilation around the battery will also reduce thermal stress on the battery and ease design of appropriate charging systems.

8.Termination
Since the exterior of the nickel-metal hydride cell is nearly identical to that of the nickel-cadmium cell, all termination procedures accepted for the nickel-cadmium cell apply equally well to the nickel-metal hydride cell. The recommendation against use of mechanical(pressure)contacts in favor of welded terminations, especially to nickel-metal hydride cells. The prohibition against soldering directly to the cell to prevent heat damage to plastic seal components also applies.

9.Other Selections Considerations
To date, applications for nickel-metal hydride cells have been focused on electronics that have nominal drain rates of 2C or less. As a result, cell internal current-carrying components such as tabs and current collectors have not been designed for high currents such as found in portable tools and appliances. Although there appear to be no intrinsic constraints on discharge rates imposed by cell chemistry, existing cell designs are for applications with maximum currents of less than 4C.

Electrochemical Processes

1.Cell Fundamentals
BOKA nickel-metal hydride cell chemistry is a hybrid of the proven positive electrode chemistry of the sealed nickel-cadmium cell with the energy storage features of metal alloys developed for advanced hydrogen energy storage concepts. This heritage in a positive-limited cell design results in batteries providing enhanced capacities while retaining the well-characterized electrical and physical design features of the sealed nickel-cadmium cell design.

2.Principle of Electrochemistry
The electrochemistry of the BOKA nickel-metal hydride cell is generally represented by the following charge and discharge reactions:
1)Charge
At the negative electrode, in the presence of the alloy and with an electrical potential applied, the water in the electrolyte is decomposed into hydrogen atoms, which are absorbed into the alloy, and hydroxyl ions as indicated below:

Alloy + H₂O + e —-Alloy (H) + OH-

At the positive electrode, the charge reaction is based on the oxidation of nickel hydroxide just as it is in the nickel-cadmium couple:

Ni(OH)₂ + OH—-NiOOH + H₂O + e
2)Discharge
At the negative electrode, the hydrogen is desorbed and combines with a hydroxyl ion to form water while also contributing an electron to the circuit:

Alloy (H) + OH- —-Alloy + H₂O + e

At the positive electrode, nickel oxyhydroxide is reduced to its lower valence state, nickel hydroxide:

NiOOH + H₂O + e—-Ni(OH)₂ + OH-

Fig.6 Schematic Discharge of BOKA Ni-MH battery

3)Overcharge:
Sealed nickel-metal hydride cells have a negative electrode with an excess of active material. on charge, the positive electrode will thus first become charged and will evolve oxygen before the negative electrode has reached a fully charged state:
At the positive electrode:

OH- —-1/4O₂ + 1/2H₂O + e

The oxygen passes through the porous separator and is reduced at the negative electrode according to the following reaction:

1/4O₂ + 1/2H₂O + e —-OH-

This is called the recombination reaction and makes the sealed nickel-metal hydride cell feasible.

4)Principle of Sealed cell:
When the battery is being charged, the positive electrode becomes fully charged first due to its small capacity. After this, overcharging occurs the reaction shown in reaction Formula 1) occurs which produces oxygen gas.

OH- —-1/2H₂O + 1/4O₂ + e ——–1)

However, at this point the negative electrode is not yet fully charged, and therefore, in theory, hydrogen gas does not form. The oxygen gas formed at the positive electrode passes though the separator, is diffuses into the negative electrode, and cause the formation o water by oxidizing the hydrogen in the hydrogen absorbing alloy which is being charged (Reaction Formula 2))

4MH + O₂ —-4M + 2H₂O ——–2)

The water formed in reaction formula 2) is consumed by the normal charging reaction (Reaction Formula 3))

Charging: M + H₂O + e —-MH + OH- ——3)

Apart from the oxygen consuming reaction of reaction formula 2), oxygen gas is also consumed by the electrochemical reaction (Reaction Formula 4))

O₂ + 2H₂O + 4e —-4OH- ——4)

In this way, the oxygen gas formed at the positive electrode is consumed at the negative electrode, making it possible to seal the Ni-MH battery.

3.Cell components
BOKA Nickel-metal hydride cells, with the exception of the negative electrode, use the same general types of components as the sealed nickel-cadmium cell.
1) Negative Electrode
The basic concept of the nickel-metal hydride cell negative electrode emanated from research on the storage of hydrogen for use as an alternative energy source in the 1970s. Certain metallic alloys were observed to form hydrides that could capture (and release) hydrogen in volumes up to nearly a thousand times their own volume. By careful selection of the alloy constituents and proportions, the thermodynamics could be balanced to permit the absorption and release process to proceed at room temperatures and pressures. The general result is shown schematically in Figure 7 where the much smaller hydrogen atom is shown absorbed into the interstices of a bimetallic alloy crystal structure.

Figure 7.Schematic of Metal-Alloy Crystal Structure Within Nickel-Metal Hydride Negative Electrode

Two general classes of metallic alloys have been identified as possessing characteristics desirable for battery cell use. These are rare earth/nickel alloys generally based around LaNi₅ (the so-called AB5 class of alloys) and alloys consisting primarily of titanium and zirconium (designated as AB2 alloys). In both cases, some fraction of the base metals is often replaced with other metallic elements. The AB5 formulation appears to offer the best set of features for commercial nickel-metal hydride cell applications.
The metal hydride electrode has a theoretical capacity approximately 40 percent higher than the cadmium electrode in a nickel-cadmium couple. As a result, nickel-metal hydride cells provide energy densities that are 20-40 percent higher than the equivalent nickel-cadmium cell.
2) Positive Electrode
The nickel-metal hydride positive electrode design draws heavily on experience with nickel-cadmium electrodes. Electrodes that are economical and rugged exhibiting excellent high-rate performance, long cycle life, and good capacity include pasted and sintered-type positive electrodes.
The balance between the positive and negative electrodes is adjusted so that the cell is always positive-limited as illustrated in Figure 8. This means that the negative electrode possesses a greater capacity than the positive. The positive will reach full capacity first as the cell is charged. It then will generate oxygen gas that diffuses to the negative electrode where it is recombined. This oxygen cycle is a highly efficient way of handling moderate overcharge currents.

Figure8.Relative Electrode Balances for Nickel-Metal Hydride Cell During Discharge/Charge/Overcharge.

3)Electrolyte
The electrolyte used in the nickel-metal hydride cell is alkaline, a dilute solution of potassium hydroxide containing other minor constituents to enhance cell performance.

4)Separator
The baseline material for the separator, which provides electrical isolation between the electrodes while still allowing efficient ionic diffusion between them, is a nylon blend similar to that currently used in many nickel-cadmium cells.

Structural Designs

The nickel-metal hydride couple lends itself to the wound construction shown in Figure 1, which is similar to that used by present-day cylindrical nickel-cadmium cells. The basic components consist of the positive and negative electrodes insulated by separators. The sandwiched electrodes are wound together and inserted into a metallic can that is sealed after injection of a small amount of electrolyte.
The general internal construction of the prismatic cell is similar to the cylindrical cell except the single positive and negative electrodes are now replaced by multiple electrode sets. Thus the trade-off for improved packaging in select applications is increased complexity in cell assembly with the corresponding increases in production cost.

Both cylindrical and prismatic nickel-metal hydride cells are typically two-piece sealed designs with metallic cases and tops that are electrically insulated from each other. The case serves as the negative terminal for the cell while the top is the positive terminal. Some finished cell designs, may use a plastic insulating wrapper shrunk over the case to provide electrical isolation between cells in typical battery applications.
In variation of this design, nickel-metal hydride cells are also being produced in prismatic versions such as that illustrated in Figure 2. The prismatic cells may fit more easily into volume-critical applications.

Fig.4 Structure Design of the Button type cell

BOKA Ni-MH batteries range in type from standard batteries to fast-charge batteries, or high temperature batteries for exclusive use as in capacity from 65 mAh to 25 Ah to meet diverse user requirements. Though each type has its own structural design according to its required performance, the basic structural design is identical.Fig.4 illustrated Construction of BOKA Button Battery.

Fig.5 Structure safety vent for BOKA Cylindrical Battery

Although BOKA Ni-MH batteries are designed to completely recombine gas generated within their casings. they have a safety vent, as illustrated in Fig.5 which opens automatically and releases. Then it is resealed so that your battery can be used again. Furthermore, because BOKA Ni-MH`s original current collector is employed for both the positive and negative tabs, internal impedance is extremely small and excellent characteristics are exhibited, even under high-rate discharge conditions.

Charge Methods

The charge method for nickel-metal hydride batteries is almost same as Ni-Cd batteries.But there is slight different between them. For this reason, a special charger is necessary. In order for a battery to be usable for a long period of time, it must be charged via the proper charge method. Various methods are used to charge rechargeable cells, but We recommends the charge methods described below to charge its nickel-metal hydride batteries.
1. Rapid charge current: 1CmA (rapid charge temperature range: 10°C to 40°C).
In order to exercise proper control to stop rapid charge, it is recommended that batteries be charged at over 0.5CmA but less than 1CmA. Charging batteries at a current in excess of 1CmA may cause the safety vent to be activated by a rise in the internal pressure of the batteries, thereby resulting in electrolyte leakage. When the temperature of the batteries is detected by a thermistor or other type of sensor, and their temperature is under 10°C or over 40°C at the commencement of the charge, then trickle charge, rather than rapid charge, must be performed. Rapid charge is stopped when any one of the values among the types of control described in (4),(5),(6) and (11) reaches the prescribed level.
2. Allowing a high current to flow to over discharged or deep-discharged batteries during charge may make it impossible to sufficiently restore the capacity of the batteries.
To charge over discharged or deep-discharged batteries, first allow a trickle current to flow, and then proceed with the rapid charge current once the battery voltage has risen.
3. Rapid charge start voltage:Approx.0.8V/cell.Rapid charge transition voltage restoration current: 0.2-0.3 CmA.
4. Peak voltage control: Approx.1.8V/cell.
The charge method is switched to trickle if the battery voltage reaches approximately 1.8V/cell due to trouble or malfunctioning of some kind.
5. DV(AV)value: 5 to 10mV/cell.
When the battery voltage drops from its peak by 5 to 10mV/cell during rapid charge, rapid charge is stopped, and the charge method is switched to trickle charge.
6. dT/dt value: Approx.1 to 2 Celsius/min.
When a rise in the battery temperature per unit time is detected by a thermistor or other type of temperature sensor during rapid charge, and the prescribed temperature rise is sensed, rapid charge is stopped and the charge method is switched over to trickle charge.
7. TCO: 55°C
The cycle life and other characteristics of batteries are impaired if the batteries are allowed to become too hot during charge. In order to safeguard against this, rapid charge is stopped and the charge method is switched over to trickle charge when the battery temperature has reached the prescribed level.
8. Initial delay timer: to 10 min.
This prevents the -AV detection circuit from being activated for a specific period of time after rapid charge has started. However, the dT/dt detection circuit is allowed to be activated during this time. As with Ni-Cd batteries, the charge voltage of nickel-metal hydride batteries may show signs of swinging (pseudo -DV) when they have been kept stand by for a long time or when they have discharged excessively, etc. The initial delay timer is needed to prevent charge from stopping (to prevent malfunctioning) due to this pseudo -AV.
9. Trickle current: 1/30 to 1/20 CmA.
When the trickle current is set higher, the temperature rise of the batteries is increased, causing the battery characteristics to deteriorate.
10. Rapid charge transfer timer: 60 min.
11. Rapid charge time: 72 min. (at 1C charge)
12. Total time: 22to 32hours.
The overcharging of nickel-metal hydride batteries, even by trickle charging, causes a deterioration in the characteristics of the batteries. To prevent overcharging by trickle charging or any other charging method, the provision of a timer to regulate the total charging time is recommended.
Recommended nickel metal hydride battery charge system*(1)Rapid charge current

(1)Rapid charge current	Max.1CmA to 0.5 /CmA
(2)Rapid charge transition voltage restoration current	0.2 to 0.3 CmA
(3)Rapid charge start voltage	Approx.0.8V/cell
(4)Charge termination voltage	1.65V/cell
(5)-AV value	5 to 10 mV/cell
(6)Battery temperature rising rate dT/dt value	1 to 2 ℃/min
(7)Maximum battery temperature TCO	55℃
(8)Initial -AV detection disabling timer	5 to 10 min
(9)Trickle current(after rapid charge)	1/30 to 1/20CmA
(10)Rapid charge transfer timer	60 min
(11)Rapid charge timer	60 min
(12)Total timer	22 to 32 hrs
(13)Rapid charge temperature range	10℃ to 40℃

*The temperature and voltage of nickel-metal hydride batteries varies depending on the shape of the battery pack, the number of cells, the arrangement of the cells and other factors. Therefore we should be consulted for more detailed information on the referenced charge control values. The charge methods described previously can be applied also when both nickel-metal hydride batteries and Ni-Cd batteries are employed in a product, but we should be consulted for the control figures and other details.

Comparison of Ni-MH and Ni-Cd Cells

Nickel-metal hydride cells are essentially an extension of the proven sealed nickel-cadmium cell technology with the substitution of a hydrogen-absorbing negative electrode for the cadmium-based electrode. While this substitution increases the cell electrical capacity(measured in ampere-hours)for a given weight and volume and eliminates the cadmium which raises toxicity concerns, the remainder of the nickel-metal hydride cell is quite similar to the nickel-cadmium product. Many application parameters are little changed between the two cell types, and replacement of nickel-cadmium cells in a battery with nickel-metal hydride cells usually involves few significant design issues.

Table1: compares key design features between the two cell chemistries.

Application Feature	Comparison of Nickel-Metal Hydride to Nickel-Cadmium Batteries
Nominal Voltage	Same(1.20V)
Discharge Capacity	Ni-MH up to 40% greater than Ni-Cd
Discharge Profile	Equivalent
Discharge Cutoff Voltages	Equivalent
High Rate Discharge Capability	Effectively the same rates
High Temperature(>35 Celsius) Discharge Capability	Ni-MH slightly better than standard Ni-Cd cells
Charging Process	Generally similar; multiple-step constant current with overcharge control recommended for fast charging Ni-MH
Charge Termination Techniques	Generally similar but Ni-MH transitions are more subtle. Backup temperature termination recommended.
Operating Temperature Limits	Similar, but with Ni-MH, cold temperature charge limit is 15℃.
Self-Discharge Rate	Ni-MH slightly higher than Ni-Cd
Cycle Life	Generally similar, but Ni-MH is more application dependent.
Mechanical Fit	Equivalent
Mechanical Properties	Equivalent
Selection of Sizes/Shapes/Capacities	Ni-MH product line more limited
Handling Issues	Similar
Environmental Issues	Reduced with Ni-MH because of elimination of cadmium toxicity concerns.

Battery Slection

The steps for selecting a type of battery for use as the power supply of a device are shown below:

1.Study of the Proposed Required Specifications
Verify the battery specifications required for the power supply of the device and use those conditions as the standards for battery selection. For reference, the technological factors concerning battery selection are shown below.

2.Battery Selection
Using the catalogs and data sheets for the batteries currently produced and marketed, narrow down the number of candidates to a few battery types. From those candidates, select the one battery that most closely satisfies the ideal conditions required. In actual practice, the selection of a battery is rarely completed as easily as this. In most cases it is necessary to consider eliminating or relaxing some of the proposed specifications, and then select the most suitable battery from among those currently available to meet the adjusted conditions. This process makes it possible to select more economical batteries.If you have any doubts at this stage, consult with BOKA.In some cases, newly improved or newly developed batteries that are not yet listed in the catalog may be available. Normally the required specifications are also finalized at this stage.

Battery Pack Design
BOKA Ni-MH 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-MH battery.

Figure 26.Installation Within Typical Application

1. Packaging Considerations
Ni-MH 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-MH 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-MH 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
Applicable Battery Size	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	Applicable Battery Size	Internal Impedance	Configuration
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-MH cells are most commonly used in battery packs. In using Ni-MH 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.