VALVE REGULATED LEAD ACID MONOBLOC BATTERY FOR
ELECTIRC & HYBRID, TWO AND THREE WHEELED VEHICLES
ABSTRACT
The present invention provides Valve Regulated Lead acid battery having improved High Rate Discharge and Deep Cycling Capability with Higher Cyclic life performance, Special alloy for the positive grids. The positive grids are formed from a lead base alloy consisting essentially of lead, from about 1.0 to about 2.0% antimony and from about 1.0 to about 2.0% cadmium, the cadmium being present in an amount at least equal to the amount of antimony present, the percentages of alloy being based on the alloy weight.
FIELD OF INVENTION
The field of invention relates to Valve Regulated lead acid batteries,
and particularly to an innovative method of providing Special alloy for positive grid and increased porosity in active materials, number of electrodes without increasing the standard dimensions of battery, which is unique of it's kind in the history of lead acid batteries.
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OBJECTIVE OF INVENTION
The present invention of the Valve Regulated lead acid batteries with Special grid alloy for positive electrode to have the advantages of providing Higher Cyclic Life with High rate / deep cycling capability to meet the requirements of Electric & Hybrid vehicles.
BACKGROUND OF INVENTION
VRLA batteries with Lead calcium alloy with more electrolyte (11 to 12 CC/Ah) are generally best suitable for low rate application (example: Telecom /stand by application of 0.1C rate of discharge). Where as applications like Electric & Hybrid vehicles required High Rate Discharge (-0.5C, almost 5 times in discharge rate compared to Lead calcium VRLA) for moderate discharge durations of about 2 hours and the battery will be cycled continuously.
Generally the Lead calcium VRLA batteries are charged with a Boost and Float voltages 2.30V and 2.25V respectively with a current limit of 0.2C maximum The Electric & Hybrid vehicles requires a battery which can be charged in faster way, so this battery needs high charge acceptance.
VRLA batteries with Lead calcium alloy are best suitable for Float applications, where the battery is continuously on charge. The Electric & Hybrid vehicle battery requires with high rate discharge capability for shorter duration (lhr 30 minutes to 2 hrs) and it require more cyclic life.
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BRIEF SUMMARY OF INVENTION
The highly desirable features for Electric & Hybrid, two and three
wheeled vehicles applications is to provide a maintenance-free battery capable of enduring repeated deep discharge cycles without any significant loss from the capacity obtained in the initial cycles.
The battery shall have a high rate discharge and deep discharge capability with more number of life cycles.
High rate discharge capability is achieved by
• Increasing active material surface area and increasing number of electrodes
• Increasing porosity in active material, which reserves the acid for reaction at sites
High charge acceptance capability is achieved by
• Increasing the conductivity of grid by using specialized alloy for Positive grid (containing antimony as special ingredient).
• Reducing the internal resistance by increasing number of electrodes there by reducing the inter electrode gap.
High cyclic life is achieved by
• Using specialized alloy in Positive grid alloy, i.e., reducing the Premature Capacity Loss due to corrosion of grid
• Special Paste technology for making 4BS paste, which will improve the cyclic life.
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Conventional Lead Antimony grid alloy (4-7 %) will have the main advantage of mechanical strength and improved cycle life with deep discharge capability and the disadvantages are
• More corrosion of positive electrode
• Antimony in Negative grid leads to more water loss due to high gassing.
• Migration of antimony to negative electrode leads reduction in performance.
The advantages of lead antimony alloy were taken into consideration by developing the specialized alloy with a less percentage of antimony (1.0 to 2.0 %) and there by reducing the negative effects were suppressed by adding the cadmium as special ingredient. This alloy is being used for positive grid
The cadmium content in the alloy of the present invention used for the positive grids should be sufficiently high so as to eliminate any significant cracking of the grids as well as providing satisfactory mechanical strength. The grid casting of low antimony lead alloys in the absence of other elements is difficult and impractical because of its "cracking" phenomenon. The addition of cadmium eliminates the cracking effect.
To insure that the overall characteristics are achieved, the cadmium should be present in an amount at least equal to the antimony content in the alloy. Based upon the total weight of the alloy, it has been found acceptable to maintain the cadmium content in the range of from about 1.0 to about 2.0%.
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DETAILED DESCRIPTION OF THE INVENTION
The Valve Regulated Monobloc Lead Acid Battery consists mainly of the following components.
The Valve Regulated Monobloc Lead Acid batteries are manufactured with 6 cells internally connected in series in a single container made of high strength, impact resistant ABS container. The cell consists of group of positive plates and negative plates connected in parallel and separated by Absorptive glass mat separator which will keep electrolyte in immobilized condition.
The grids were be made on Gravity casting machine with specialized alloy. This alloy consists of 1.5 to 2% of antimony and 1 to 2% cadmium and is being used for positive grid casting.
Then the Paste will be prepared by using fully automatic paste mixers,
which will take care of 4BS paste. Then the paste will be applied on grids
using belt-pasting machine.
The pasted plates will be cured at 80°C for 24 hrs and then dried.
The cured and dried plates are assembled into battery by joining positive
and negative in stacks, and then put into container and lid will fixed using
glue.
The glued battery will be filled with Electrolyte (with additives sodium
sulfate) by using vacuum filling machine.
Then batteries will be formed and tested for required high rate discharge
(2hr duration @ 5Ampers up to the End Voltage of 10.5V).
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BRIEF DESCRIPTION OF DRAWINGS
1. Battery cutoff view of internal components with ready plug in terminals. (Fig 1)
CLAIMS
We claim the following
Valve regulated Monobloc lead acid battery with Specialized alloy provide the following mutual benefits of Lead antimony and VRLA
1. High rate discharge capability - 0.5C cycling. This is
achieved by
a. Using the Specialized alloy for positive with 1-2%
antimony and 1-2% cadmium.
b. Higher Positive to Negative active material ratio (1.4 -
1.6).
c. Paste with 4BS technology.
2. More than 98 % gas recombination.
a. Usage Absorptive Glass Mat Separator with Starved
increases the gas recombination efficiency.
b. Electrolyte with additive of Potassium Sulfate (0.5%)
3. Long cycle life without any water top up.
a. Using the Specialized alloy for positive with 1-2%
antimony and 1-2% cadmium
b. Higher Positive to Negative active material ratio (1.4 -
1.6).
c. Usage Absorptive Glass Mat Separator with micro
pores (ISmicrons average).
4. Vibration resistant and suitable for Electric Vehicle
applications.
a. High separator compression 50 to 60 Kpa, which will hold stacks in tight condition.
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