1.Overview top
Rechargeable Ni-Cd & Ni-MH batteries are one type of alkaline storage battery, which is classified as a secondary battery.
Giving top priority to meeting the needs of our customers, Firstar will continue to develop new products for providing power to the devices that are so important to today's comfortable, enjoyable, and productive living.
2. Features top
A. Long Life
Firstar rechargeable batteries 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
Firsar rechargeable 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.
C. Long Shelf Life
Firstar rechargeable batteries 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 in1~6 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 65℃
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 our original sealing compound, there is no liquid leakage!
4.Construction top
The Firstar cell consists of positive and negative plates, separator, alkaline electrolyte, metal case, and sealing plate with self-resealing safety vent a case is constructed of nickel-plated steel, welded internally to the negative plate. It becomes the negative pole.
5.Electrochemical Processes top
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:
Nickel-metal hydride batteries employ nickel hydroxide for the positive electrode similar to Ni-Cd batteries. The hydrogen is stored in a hydrogen-absorbing alloy for the negative electrode, and an aqueous solution consisting mainly of potassium hydroxide for the electrolyte. Their charge and discharge reactions are shown below.
6.Charging Methods top
There are various methods charging Firstar batteries. 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.
6.1 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
6.2 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 Firstar batteries because the circuit configuration is simple, and less expensive. An example of this circuit plan is illustrated in Fig.2. 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.
6.3 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 Unitech batteries used in fire alarms and emergency lighting. Fig.3 is an example of trickle charge circuit.
6.4 Floating Charge
The Firstar 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 4 illustrates the block diagram for floating charge where the resistance should be adjusted so the current will be equal to the specified rate.
6.5 - ΔV Detection Control System
Under this system, the charge current is controlled by detecting the decrease ( V) in the cell voltage at the end of charging.
Fig.5 shows an outline of the -ΔV 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.
6.6 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.
6.6.1 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.
6.6.2 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.
6.6.3 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.
6.6.4 Designing The Detection Circuit
There are various detection circuits in use, as described in chapter 4. 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 Firstar.
6.7 Parallel Charge and Parallel Discharge
When charged in parallel, the difference in charger voltage among Firstar batteries causes larger current flow into the cell with less charge voltage. The charge voltage of the Firstar 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.6
The slight difference in cell voltage in Firstar 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.7
7. Precautions For Using Firstar Battery top
In order to take full advantage of the properties of Unitech batteries and also to prevent problems due to improper use, please note the following points during the using and designing of the battery operated products.
7.1 Charging
A Charging temperature
· Charge batteries within an ambient temperature range of 0°C to 45°C.
· Ambient temperature during charging affects charging efficiency. As charging efficiency is best within a temperature range of 10°C to 30°C,
whenever possible please place the charger (battery pack) in a location within the specified temperature range.
· At temperatures below 0°C 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.
· Charging efficiency drops at temperatures above 40°C. This can disturb full charging and lead to deterioration in performance and battery leakage.
B Parallel charging of batteries
· Sufficient care must be taken during the design of the charger when charging batteries connected in parallel. Consult Firstar when parallel charging is required.
C Reverse charging
·?Never attempt reverse charging.
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, leading to alkaline electrolyte leakage, rapid deterioration in cell performance, battery swelling or battery bursts.
D Overcharging
· Avoid overcharging. Repeated overcharging can lead to deterioration in battery performance.
("Overcharging" means charging a battery when it is already fully charged.)
E Rapid Charging
· To charge batteries rapidly, use the specified charger (or charging method recommended by Firstar) and follow the correct procedures.
F Trickle charging (continuous charging)
· Carry out trickle charge by applying the current of 0.02 to 0.05 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.
7.2. Discharging
A. Discharge temperature
· Discharge batteries within an ambient temperature range of -20°C to +65°C.
· Discharge current level (i.e. the current at which a battery is discharged) affects discharging efficiency. Discharging efficiency is good within a current range of 0.1 CmA to 0.5 CmA.
· Discharge capacity drops at temperatures below -20°C or above +65°C. Such decreases in discharge capacity can lead to deterioration in battery performance.
B. Overdischarge
· Since overdischarging 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 long periods of time. Also, avoid shipping the battery installed in the equipment.
C High-current discharging
· As high-current discharging can lead to heat generation and decreased discharging efficiency, please consult Firstar before attempting continuous discharging or pulse discharging at
currents larger than 2 CmA.
7.3. Storage
A. Storage temperature and humidity (short-term)
Store batteries in a dry location with low humidity, no corrosive gases, and at a temperature range of -20°C to +45°C.
· Storing batteries in a location where humidity is extremely high or where temperatures fall below -2?°C or rise above +4?°C can lead to the rusting of metallic parts and battery leakage due to expansion or contraction in parts composed of organic materials.
B. Long-term storage (2 year, -20°C to +35°C)
Because long-term storage can accelerate battery self-discharge and lead to the deactivation of reactants, locations where the temperature ranges between +10°C and +30°C are suitable for long-term storage.
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.
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 voltage detection type battery charger carry out charge and discharge at least once every 6 months.
7.4. Service Life of Batteries
A. 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 unusual in-crease 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. Please contact Firstar if you have any questions.
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 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.
7.5 Design of Products Which Use Batteries
A. Connecting batteries and products
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. 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.
Use caution in applying pressure to the terminals in cases where the battery pack can be separated from the equipment.
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.
B. Material for terminals in products using the batteries
Because small amounts of alkaline electrolyte can leak out from the battery seal during extended use or when the safety vent is activated during improper use, use a highly alkaline-resistant material 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. NOTE that stainless steel generally results in higher contact resistance.
C. Temperature related to the position of batteries in products
Excessively high temperatures (i.e. higher than 45°C) 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 product. The best battery position is a battery compartment that is composed of an alkaline-resistant material which isolates the batteries from the product's circuitry. This prevents damage caused by a slight leakage of alkaline electrolyte from the battery. Be careful particularly when trickle charging is carried out (for continuous charging).
D. 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 cut off circuit is recommended in order to avoid overdischarge and reverse charge.
The discharge end voltage is determined by the formula given below.
Numbers of Batteries Arranged Serially
1 to 6 (Number of batteries ×1.0)V
7 to 20 ((Number of batteries-1)×1.2)V
E Overdischarge (deep discharge) prevention
Overdischarging (deep discharging) or reverse charging damages the battery characteristics. In order to prevent damage associated with forget-ting to turn off the switch or leaving the battery in the equipment for extended periods, it is hoped that preventative options are incorporated in the equipment. At the same time, it is recommended that leakage current is minimized. Also, the battery should not be shipped inside the equipment.
7.6 Prohibited Items Regarding the Battery Handling
Firstar assumes no responsibility for problems resulting from batteries handled in the following manner.
A. Disassembly
Never disassemble a battery, as the electrolyte inside is strong alkaline and can damage skin and clothes.
B. Short-circuiting
Never attempt to short-circuit a battery. Doing so can damage the product and generate heat that can cause burns.
C. 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.
D. 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.
E. 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.
F. Overcharging at high currents and reverse charging
Never reverse charge or overcharge with high currents (i.e. higher than rated). Doing so causes rapid gas generation and increased gas pres-sure, thus causing batteries to swell or rupture.
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.
G. Installation in equipment (with an airtight battery compartment)
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.).
H. 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.
I. Short-circuiting of battery packs
Special caution is required to prevent short-circuits. Care must be taken during the design of the battery pack shape to ensure batteries cannot be inserted in reverse. Also, caution must be given to certain structures or product terminal shapes which can make short-circuiting more likely.
J. Using old and new batteries together
Avoid using old and new batteries together. Also avoid using these batteries with ordinary dry-cell batteries, Ni-MH batteries or with another manufacturer's batteries. Differences in various characteristic values, etc., can cause damage to batteries or the product.
7.7 Other Precautions
Batteries should always be charged prior to use. Be sure to charge correctly.
7.8 Final Point to Bear in Mind
In order to ensure safe battery use and to prolong the battery performance, please consult Firstar regarding charge and discharge conditions for use and product design prior to the release of a battery-operated product.
8. General Recommendations for use top
Firstar cells do not require most of the cautions for handing and use that are necessary for most other rechargeable cells . the cell is a maintenance-free battery. The following is a basic description of how to use the Firstar cell in order to obtain maximum performance and service life . Because the range of applications for the Firstar cell is extremely wide , please contact us if your application exceeds the general methods described here. Unless stated otherwise, the values given are for the standard type cell . For other types, please refer to the individual data sheets .
8.1 Incoming Inspection
(A) Firstar cells are generally shipped in the discharged condition , but can be shipped in the charged condition if requested before.
(B) The voltage in such instances may fluctuate depending upon the degree of the discharge . these cells are normal if the voltage as received is 1.0V/cell, for cells shipped are discharged .If the voltage is 1.20V/cell or higher , it is normal , for cells shipped are charged.
(C) It is recommended, when a shipment is received, that a test is made to determine whether the open circuit voltage of the cells is in the range just specified.
(D) If a capacity test is to be made , first partially discharge the residual capacity, and then charge for 16 hours at C/10 at room temperature . Capacity is checked by discharging at C/5 to 1.0V/cell. The cell is normal if the specified capacity is achieved within 1～3 charge/discharge cycles.
Note: For cells received in the discharged condition, begin with charging. 〔Test temperature ;20±5℃(68°±9°F) 〕
8.2 Temperature Conditions
A. Charge
Charge should be conducted as previously described in " Charging Methods"(Paragraph 1.7.) Consult with Firstar regarding any other charging methods .
(1) Charging temperatures range are:
● Standard charge :0° to 45℃ (32° to 113℃)
● Quick charge :10° to 45℃ (50° to 113℉)
● Trickle(float) charge: 0° to 65℃ (32° to 149℉)
● Rapid charge
(-△V method): 10° to 45℃ (50° to 113℉)
● Temperature sensing system:
10° to 40℃ (50° to 104℉)
Charge conducted at temperatures outside of these ranges, will have an adverse influence on cell life. In particular ,when charging at low temperatures , hydrogen may be generated. If a sealed battery pack is used, ventilation holes should be provided for safety .
(2) Even within the specified temperature range, cell life will be shortened if charging is always conducted at the low or high end of the temperature range .For longest life .it is recommended that charging be conducted at an average temperature of 20° to 30℃(68° to 86℉).
B. Discharge
Discharge temperature ranges are -20° to ＋65℃ (-4° to ＋140℉). Please consult Unitech regarding use beyond these temperature conditions ,or for discharge currents beyond those specified in data sheets . Because service life will be decreased by repeated discharges at extreme temperature, discharge between 20°(68°) and 30℃ (86℉) are recommended.
C. Storage
(A) Firstar cells can withstand very long storage time under typical conditions at a storage time under typical of -20° to ＋45℃ (-4° to ＋113℉).If the cell must provide full capacity after storage ,completely charge the cell before use . In addition, after prolonged storage , completely normal capacity can be returned within 1～3 charge/discharge cycles.
(B) It is recommended that the "R" type cell be stored in the discharged condition . It can be quickly recharged back to normal capacity.
(B) Batteries should not be stored continuously in a high temperature environment .Cell characteristics can best be retained if storage is maintained at an average temperature of 30℃ (86℉) or less.
Note: please consult Unitech for use in temperature beyond these conditions.
8.3 Cell Reversal
In general, cell reversal should be avoided. If several cells are to be connected in series, it is suggested that they have similar ("matched") capacities. Huanyu automatically matches cells when making battery pack assemblies, and at no extra charge. Where discharge currents will be high ,or prolonged, and cell reversal can be anticipated, a low-voltage cut-off is suggested. when using a low voltage cut -off, cut-off of 1.0V/cell is recommended.
8.4 Short-circuit Protection
Because the internal resistance of Firstar cells is extremely small ,a short-circuit will produce very big current ..A Current equivalent to 30～50 times the rated capacity will flow, resulting in heat generation and damage to the cell's insulator and surrounding parts. Therefore, It is important to make sure that a short-circuit does not occur when and after cells are installed in equipment . the use of a fuse or a resettable thermostat in the battery circuit is recommended.
8.5 Packaging and Terminals
(A) Firstar offers pre-assembled battery pack ,or cells equipped with solder tabs. If you do your own assemblies, do not solder directly to the cell. Use solder tabs.
(B) Single cells should be insulated . It is recommended that packs have an outer plastic cover or case for convenience in handling .
(C) As protection in the unlikely event that gas might be generated, batteries should not be placed in totally sealed equipment; air ventilation holes should be provided.
8.6 Severe Use Applications
Temperature, charging, discharging and storage have been discussed, but each of these s related to time. The Firstar cell can be used even at 85oC(185oF), if only for a short time. But, because life will obviously be shortened if use is continued under such extreme conditions, use at extreme temperature for longer period should be avoided.
Note: Please consult Firstar for application beyond specified operating parameters.
9. Explainable top
Cell Failure
Firstar cells are manufactured under strict quality control conditions. Every effort is exerted to assure that failure will not occur. However, because the cells are used in a wide range of applications and conditions, it is inevitable that some failures will occur.
There are two types of cell failure: reversible and permanent.
A Reversible Failure
In a typical Ni-Cd & Ni-MH cell, either long term storage, or prolonged charging at high temperature will result in lowered cell capacity. This is normally seen as a slight decrease in the average cell voltage. This loss of capacity can be removed by a full charge for stored cells, or 1-3 charge/discharge cycles for cells that have been on long term trickle charge.
B Permanent Failure
Failure due to aging occur when there are very large numbers of charge/discharge cycles, and particularly where the charge or discharge takes place beyond specified operating ranges.
Failure also will occur after storage for several years at continuous high temperature, through deep cell reversal, or if a trickle charge is applied for an extended period (close to 7-10 years). A cell is considered to have reached the end of its normal life when it fails to yield 80% of its original rated capacity.
Care in Handling
A Battery Connection to Electric Equipment
Direct soldering of lead to the cell can cause damage to the separator, safety vent, insulator or other parts, due to heat. Do not solder the lead wires directly to the battery. Spot weld the tab to the battery and solder the lead wire to the tab.
B Parallel Charging Connection
Parallel charging can produce irregular charging currents, and battery performance can be lowered by short or excess charging. Avoiding charging batteries in parallel. If batteries are discharged in parallel, use protective diodes between them to avoid back discharge from one battery into the other.
C Contact Terminals
Use battery holders and other contact materials made of nickel or nickel-plated steel. Copper, zinc, chrome or aluminum contacts should be avoided, as they tend to be prone to corrosion.
D Battery Position
Place the battery apart from any heat sources in the equipment. When placed near a heat source, the performance of the battery drops as its temperature is raised.
E Used in Sealed Equipment
Do not put the battery in a totally sealed case or equipment.
F Disassembly
Do not disassemble the battery. It contains electrolyte which can cause injury to clothing or skin, In the event that electrolyte gets on skin or in eyes, please immediately flush with pure water and see a doctor.
G Handling
Do not pull on battery lead wires or connector. Excess force on the leads or connector can damage the solder joints or other connections.
H Short Circuit
Do not short circuit the battery, Short circuiting the battery produces very high currents which can damage the battery or the equipment.
I Dispose in Fire
Do not dispose of the battery in a fire or incinerator. Disposal in this manner can cause the battery to explode.
J Use of Mixed Cells and Types
Do not use different types of batteries in the same battery assembly. The mixed use of dry cells, old and new cells, or cells of varying sizes in the same battery assembly can damage the battery or the equipment, due to varying electrical characteristics and capabilities.
Rechargeable Ni-Cd & Ni-MH batteries are one type of alkaline storage battery, which is classified as a secondary battery.
Giving top priority to meeting the needs of our customers, Firstar will continue to develop new products for providing power to the devices that are so important to today's comfortable, enjoyable, and productive living.
2. Features top
A. Long Life
Firstar rechargeable batteries 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
Firsar rechargeable 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.
C. Long Shelf Life
Firstar rechargeable batteries 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 in1~6 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 65℃
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 our original sealing compound, there is no liquid leakage!
4.Construction top
The Firstar cell consists of positive and negative plates, separator, alkaline electrolyte, metal case, and sealing plate with self-resealing safety vent a case is constructed of nickel-plated steel, welded internally to the negative plate. It becomes the negative pole.
5.Electrochemical Processes top
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:
Nickel-metal hydride batteries employ nickel hydroxide for the positive electrode similar to Ni-Cd batteries. The hydrogen is stored in a hydrogen-absorbing alloy for the negative electrode, and an aqueous solution consisting mainly of potassium hydroxide for the electrolyte. Their charge and discharge reactions are shown below.
6.Charging Methods top
There are various methods charging Firstar batteries. 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.
6.1 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
6.2 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 Firstar batteries because the circuit configuration is simple, and less expensive. An example of this circuit plan is illustrated in Fig.2. 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.
6.3 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 Unitech batteries used in fire alarms and emergency lighting. Fig.3 is an example of trickle charge circuit.
6.4 Floating Charge
The Firstar 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 4 illustrates the block diagram for floating charge where the resistance should be adjusted so the current will be equal to the specified rate.
6.5 - ΔV Detection Control System
Under this system, the charge current is controlled by detecting the decrease ( V) in the cell voltage at the end of charging.
Fig.5 shows an outline of the -ΔV 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.
6.6 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.
6.6.1 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.
6.6.2 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.
6.6.3 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.
6.6.4 Designing The Detection Circuit
There are various detection circuits in use, as described in chapter 4. 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 Firstar.
6.7 Parallel Charge and Parallel Discharge
When charged in parallel, the difference in charger voltage among Firstar batteries causes larger current flow into the cell with less charge voltage. The charge voltage of the Firstar 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.6
The slight difference in cell voltage in Firstar 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.7
7. Precautions For Using Firstar Battery top
In order to take full advantage of the properties of Unitech batteries and also to prevent problems due to improper use, please note the following points during the using and designing of the battery operated products.
7.1 Charging
A Charging temperature
· Charge batteries within an ambient temperature range of 0°C to 45°C.
· Ambient temperature during charging affects charging efficiency. As charging efficiency is best within a temperature range of 10°C to 30°C,
whenever possible please place the charger (battery pack) in a location within the specified temperature range.
· At temperatures below 0°C 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.
· Charging efficiency drops at temperatures above 40°C. This can disturb full charging and lead to deterioration in performance and battery leakage.
B Parallel charging of batteries
· Sufficient care must be taken during the design of the charger when charging batteries connected in parallel. Consult Firstar when parallel charging is required.
C Reverse charging
·?Never attempt reverse charging.
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, leading to alkaline electrolyte leakage, rapid deterioration in cell performance, battery swelling or battery bursts.
D Overcharging
· Avoid overcharging. Repeated overcharging can lead to deterioration in battery performance.
("Overcharging" means charging a battery when it is already fully charged.)
E Rapid Charging
· To charge batteries rapidly, use the specified charger (or charging method recommended by Firstar) and follow the correct procedures.
F Trickle charging (continuous charging)
· Carry out trickle charge by applying the current of 0.02 to 0.05 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.
7.2. Discharging
A. Discharge temperature
· Discharge batteries within an ambient temperature range of -20°C to +65°C.
· Discharge current level (i.e. the current at which a battery is discharged) affects discharging efficiency. Discharging efficiency is good within a current range of 0.1 CmA to 0.5 CmA.
· Discharge capacity drops at temperatures below -20°C or above +65°C. Such decreases in discharge capacity can lead to deterioration in battery performance.
B. Overdischarge
· Since overdischarging 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 long periods of time. Also, avoid shipping the battery installed in the equipment.
C High-current discharging
· As high-current discharging can lead to heat generation and decreased discharging efficiency, please consult Firstar before attempting continuous discharging or pulse discharging at
currents larger than 2 CmA.
7.3. Storage
A. Storage temperature and humidity (short-term)
Store batteries in a dry location with low humidity, no corrosive gases, and at a temperature range of -20°C to +45°C.
· Storing batteries in a location where humidity is extremely high or where temperatures fall below -2?°C or rise above +4?°C can lead to the rusting of metallic parts and battery leakage due to expansion or contraction in parts composed of organic materials.
B. Long-term storage (2 year, -20°C to +35°C)
Because long-term storage can accelerate battery self-discharge and lead to the deactivation of reactants, locations where the temperature ranges between +10°C and +30°C are suitable for long-term storage.
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.
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 voltage detection type battery charger carry out charge and discharge at least once every 6 months.
7.4. Service Life of Batteries
A. 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 unusual in-crease 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. Please contact Firstar if you have any questions.
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 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.
7.5 Design of Products Which Use Batteries
A. Connecting batteries and products
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. 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.
Use caution in applying pressure to the terminals in cases where the battery pack can be separated from the equipment.
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.
B. Material for terminals in products using the batteries
Because small amounts of alkaline electrolyte can leak out from the battery seal during extended use or when the safety vent is activated during improper use, use a highly alkaline-resistant material 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. NOTE that stainless steel generally results in higher contact resistance.
C. Temperature related to the position of batteries in products
Excessively high temperatures (i.e. higher than 45°C) 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 product. The best battery position is a battery compartment that is composed of an alkaline-resistant material which isolates the batteries from the product's circuitry. This prevents damage caused by a slight leakage of alkaline electrolyte from the battery. Be careful particularly when trickle charging is carried out (for continuous charging).
D. 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 cut off circuit is recommended in order to avoid overdischarge and reverse charge.
The discharge end voltage is determined by the formula given below.
Numbers of Batteries Arranged Serially
1 to 6 (Number of batteries ×1.0)V
7 to 20 ((Number of batteries-1)×1.2)V
E Overdischarge (deep discharge) prevention
Overdischarging (deep discharging) or reverse charging damages the battery characteristics. In order to prevent damage associated with forget-ting to turn off the switch or leaving the battery in the equipment for extended periods, it is hoped that preventative options are incorporated in the equipment. At the same time, it is recommended that leakage current is minimized. Also, the battery should not be shipped inside the equipment.
7.6 Prohibited Items Regarding the Battery Handling
Firstar assumes no responsibility for problems resulting from batteries handled in the following manner.
A. Disassembly
Never disassemble a battery, as the electrolyte inside is strong alkaline and can damage skin and clothes.
B. Short-circuiting
Never attempt to short-circuit a battery. Doing so can damage the product and generate heat that can cause burns.
C. 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.
D. 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.
E. 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.
F. Overcharging at high currents and reverse charging
Never reverse charge or overcharge with high currents (i.e. higher than rated). Doing so causes rapid gas generation and increased gas pres-sure, thus causing batteries to swell or rupture.
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.
G. Installation in equipment (with an airtight battery compartment)
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.).
H. 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.
I. Short-circuiting of battery packs
Special caution is required to prevent short-circuits. Care must be taken during the design of the battery pack shape to ensure batteries cannot be inserted in reverse. Also, caution must be given to certain structures or product terminal shapes which can make short-circuiting more likely.
J. Using old and new batteries together
Avoid using old and new batteries together. Also avoid using these batteries with ordinary dry-cell batteries, Ni-MH batteries or with another manufacturer's batteries. Differences in various characteristic values, etc., can cause damage to batteries or the product.
7.7 Other Precautions
Batteries should always be charged prior to use. Be sure to charge correctly.
7.8 Final Point to Bear in Mind
In order to ensure safe battery use and to prolong the battery performance, please consult Firstar regarding charge and discharge conditions for use and product design prior to the release of a battery-operated product.
8. General Recommendations for use top
Firstar cells do not require most of the cautions for handing and use that are necessary for most other rechargeable cells . the cell is a maintenance-free battery. The following is a basic description of how to use the Firstar cell in order to obtain maximum performance and service life . Because the range of applications for the Firstar cell is extremely wide , please contact us if your application exceeds the general methods described here. Unless stated otherwise, the values given are for the standard type cell . For other types, please refer to the individual data sheets .
8.1 Incoming Inspection
(A) Firstar cells are generally shipped in the discharged condition , but can be shipped in the charged condition if requested before.
(B) The voltage in such instances may fluctuate depending upon the degree of the discharge . these cells are normal if the voltage as received is 1.0V/cell, for cells shipped are discharged .If the voltage is 1.20V/cell or higher , it is normal , for cells shipped are charged.
(C) It is recommended, when a shipment is received, that a test is made to determine whether the open circuit voltage of the cells is in the range just specified.
(D) If a capacity test is to be made , first partially discharge the residual capacity, and then charge for 16 hours at C/10 at room temperature . Capacity is checked by discharging at C/5 to 1.0V/cell. The cell is normal if the specified capacity is achieved within 1～3 charge/discharge cycles.
Note: For cells received in the discharged condition, begin with charging. 〔Test temperature ;20±5℃(68°±9°F) 〕
8.2 Temperature Conditions
A. Charge
Charge should be conducted as previously described in " Charging Methods"(Paragraph 1.7.) Consult with Firstar regarding any other charging methods .
(1) Charging temperatures range are:
● Standard charge :0° to 45℃ (32° to 113℃)
● Quick charge :10° to 45℃ (50° to 113℉)
● Trickle(float) charge: 0° to 65℃ (32° to 149℉)
● Rapid charge
(-△V method): 10° to 45℃ (50° to 113℉)
● Temperature sensing system:
10° to 40℃ (50° to 104℉)
Charge conducted at temperatures outside of these ranges, will have an adverse influence on cell life. In particular ,when charging at low temperatures , hydrogen may be generated. If a sealed battery pack is used, ventilation holes should be provided for safety .
(2) Even within the specified temperature range, cell life will be shortened if charging is always conducted at the low or high end of the temperature range .For longest life .it is recommended that charging be conducted at an average temperature of 20° to 30℃(68° to 86℉).
B. Discharge
Discharge temperature ranges are -20° to ＋65℃ (-4° to ＋140℉). Please consult Unitech regarding use beyond these temperature conditions ,or for discharge currents beyond those specified in data sheets . Because service life will be decreased by repeated discharges at extreme temperature, discharge between 20°(68°) and 30℃ (86℉) are recommended.
C. Storage
(A) Firstar cells can withstand very long storage time under typical conditions at a storage time under typical of -20° to ＋45℃ (-4° to ＋113℉).If the cell must provide full capacity after storage ,completely charge the cell before use . In addition, after prolonged storage , completely normal capacity can be returned within 1～3 charge/discharge cycles.
(B) It is recommended that the "R" type cell be stored in the discharged condition . It can be quickly recharged back to normal capacity.
(B) Batteries should not be stored continuously in a high temperature environment .Cell characteristics can best be retained if storage is maintained at an average temperature of 30℃ (86℉) or less.
Note: please consult Unitech for use in temperature beyond these conditions.
8.3 Cell Reversal
In general, cell reversal should be avoided. If several cells are to be connected in series, it is suggested that they have similar ("matched") capacities. Huanyu automatically matches cells when making battery pack assemblies, and at no extra charge. Where discharge currents will be high ,or prolonged, and cell reversal can be anticipated, a low-voltage cut-off is suggested. when using a low voltage cut -off, cut-off of 1.0V/cell is recommended.
8.4 Short-circuit Protection
Because the internal resistance of Firstar cells is extremely small ,a short-circuit will produce very big current ..A Current equivalent to 30～50 times the rated capacity will flow, resulting in heat generation and damage to the cell's insulator and surrounding parts. Therefore, It is important to make sure that a short-circuit does not occur when and after cells are installed in equipment . the use of a fuse or a resettable thermostat in the battery circuit is recommended.
8.5 Packaging and Terminals
(A) Firstar offers pre-assembled battery pack ,or cells equipped with solder tabs. If you do your own assemblies, do not solder directly to the cell. Use solder tabs.
(B) Single cells should be insulated . It is recommended that packs have an outer plastic cover or case for convenience in handling .
(C) As protection in the unlikely event that gas might be generated, batteries should not be placed in totally sealed equipment; air ventilation holes should be provided.
8.6 Severe Use Applications
Temperature, charging, discharging and storage have been discussed, but each of these s related to time. The Firstar cell can be used even at 85oC(185oF), if only for a short time. But, because life will obviously be shortened if use is continued under such extreme conditions, use at extreme temperature for longer period should be avoided.
Note: Please consult Firstar for application beyond specified operating parameters.
9. Explainable top
Cell Failure
Firstar cells are manufactured under strict quality control conditions. Every effort is exerted to assure that failure will not occur. However, because the cells are used in a wide range of applications and conditions, it is inevitable that some failures will occur.
There are two types of cell failure: reversible and permanent.
A Reversible Failure
In a typical Ni-Cd & Ni-MH cell, either long term storage, or prolonged charging at high temperature will result in lowered cell capacity. This is normally seen as a slight decrease in the average cell voltage. This loss of capacity can be removed by a full charge for stored cells, or 1-3 charge/discharge cycles for cells that have been on long term trickle charge.
B Permanent Failure
Failure due to aging occur when there are very large numbers of charge/discharge cycles, and particularly where the charge or discharge takes place beyond specified operating ranges.
Failure also will occur after storage for several years at continuous high temperature, through deep cell reversal, or if a trickle charge is applied for an extended period (close to 7-10 years). A cell is considered to have reached the end of its normal life when it fails to yield 80% of its original rated capacity.
Care in Handling
A Battery Connection to Electric Equipment
Direct soldering of lead to the cell can cause damage to the separator, safety vent, insulator or other parts, due to heat. Do not solder the lead wires directly to the battery. Spot weld the tab to the battery and solder the lead wire to the tab.
B Parallel Charging Connection
Parallel charging can produce irregular charging currents, and battery performance can be lowered by short or excess charging. Avoiding charging batteries in parallel. If batteries are discharged in parallel, use protective diodes between them to avoid back discharge from one battery into the other.
C Contact Terminals
Use battery holders and other contact materials made of nickel or nickel-plated steel. Copper, zinc, chrome or aluminum contacts should be avoided, as they tend to be prone to corrosion.
D Battery Position
Place the battery apart from any heat sources in the equipment. When placed near a heat source, the performance of the battery drops as its temperature is raised.
E Used in Sealed Equipment
Do not put the battery in a totally sealed case or equipment.
F Disassembly
Do not disassemble the battery. It contains electrolyte which can cause injury to clothing or skin, In the event that electrolyte gets on skin or in eyes, please immediately flush with pure water and see a doctor.
G Handling
Do not pull on battery lead wires or connector. Excess force on the leads or connector can damage the solder joints or other connections.
H Short Circuit
Do not short circuit the battery, Short circuiting the battery produces very high currents which can damage the battery or the equipment.
I Dispose in Fire
Do not dispose of the battery in a fire or incinerator. Disposal in this manner can cause the battery to explode.
J Use of Mixed Cells and Types
Do not use different types of batteries in the same battery assembly. The mixed use of dry cells, old and new cells, or cells of varying sizes in the same battery assembly can damage the battery or the equipment, due to varying electrical characteristics and capabilities.