TITLE OF THE INVENTION: ALLOY FOR LEAD ACID BATTERY GRIDS

FIELD OF THE INVENTION
The present invention relates to an alloy for lead acid battery grids.
BACKGROUND OF THE INVENTION
The grids of lead acid batteries are usually made of alloys. As a standard practice, such alloys contain antimony, arsenic, tin, selenium, and lead, or calcium, tin and lead in varying proportions. Optionally, invariably, the alloys may also contain other metals such as sulphur, silver, copper, bismuth, and alkali metals.
While antimony helps in the hardening of the alloys, which in turn helps in subsequent processes such as gravity casting, it also accelerates the rate at which water is lost from the battery electrolyte. For example, the rate of water loss when antimony is present in both the positive and negative plate may reach up to 5 grams per Ampere hour at a constant voltage charging of 14.40 V @ 40 degrees Centigrade for 500 hours for a 12 V battery. Similarly, when antimony is present in the positive plate and calcium is present in the negative plate, the rate of water loss may reach up to 2.5 grams per Ampere hour under similar test conditions (as that of antimony). This water loss leads to a decline in battery performance and an increase in maintenance costs. Further, the presence of antimony leads to increased gassing and self discharge rate and may also result in accidental explosions.
Another problem faced conventionally (especially in automotive applications) is corrosion of the positive grid; this corrosion is particularly rapid in vehicles whose engine compartments reach high temperature. Corrosion also gives rise to growth-creep, caused by tensile strain, and leads to increased electrical resistance and reduced discharge performance. High temperatures in the operating environment will result in synergistic acceleration of corrosion and growth-creep, and this will have a significant impact on battery life.
There is therefore a need in the art for an alloy for lead acid battery grids that solves the above mentioned drawbacks and has the below mentioned objectives.
OBJECTIVES OF THE PRESENT INVENTION
The objective of the present invention is to provide an alloy for lead acid battery grids that is free of antimony, which has the following characteristics:

• is resistant to corrosion;
• increases performance and life of the battery;
• reduces maintenance costs;
• has a high current charge-discharge characteristic; and
• reduces gassing and thus minimizes the chances of accidental explosions.
• low self-discharge
SUMMARY OF THE INVENTION
To overcome the drawbacks of the prior art and achieve the above mentioned objectives, an alloy for lead acid battery grids is disclosed, said alloy comprising tin in the range of 0.1-10 percent by weight, arsenic in the range of 0.01-4 percent by weight and selenium in the range of 0.01-3 percent by weight, with the remaining alloy comprising lead along with other unavoidable impurities. The disclosed alloy is free of antimony, is resistant to corrosion, increases performance and life of the battery, reduces the self-discharge rate, reduces maintenance costs and reduces gassing, thus minimizing the chances of accidental explosions.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this specification, the use of the words "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
In one embodiment, the present invention relates to an alloy for lead acid battery grids, said alloy comprising tin in the range of 0.1-10 percent by weight, arsenic in the range of 0.01-4 percent by weight, and selenium in the range of 0.01-3 percent by weight, with the remaining alloy comprising lead along with other unavoidable impurities.
In a preferred embodiment, the alloy comprises tin in the range of 0.5-2 percent by weight, arsenic in the range of 0.05-0.25 percent by weight, selenium in the range of 0.01-0.05 percent by weight, with the remaining alloy comprising lead along with other unavoidable impurities.

Further, in a more preferred embodiment, the alloy comprises 1 percent by weight of tin, 0.15 percent by weight of arsenic, 0.03 percent by weight of selenium, with the remaining alloy comprising lead along with other unavoidable impurities.
The disclosed alloy for led acid battery grids can be used in casting of grids using conventional gravity casting machines, with improved hardness. The manufactured grids have uniform grain structure and corrode at a significantly much slower rate rather than grids produced conventionally. The absence of antimony in the alloy eliminates gassing, reduces self-discharge and results in low water loss and thus avoids accidental explosions. Using the disclosed alloy, water loss rates as low as 1.2 grams per Ampere hour have been achieved. The lead acid battery grid is preferably of the flooded type.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the spirit and the scope of the invention may be made by a person skilled in the art.

We Claim
1. An alloy for lead acid battery grids, comprising 01.-10% by weight of tin, 0.01-4 percent by weight of arsenic, and 0.01-3% by weight of selenium, with the remaining alloy comprising lead along with other unavoidable impurities.
2. An alloy for lead acid battery grids as claimed in claim 1, comprising 0.5-2% by weight of tin, 0.05-0.25% by weight of arsenic, and 0.01-0.05% by weight of selenium, with the remaining alloy comprising lead along with other unavoidable impurities.
3. An alloy for lead acid battery grids as claimed in claim 2, comprising 1% by weight of tin, 0.15% by weight of arsenic, and 0.03% by weight of selenium, with the remaining alloy comprising lead along with other unavoidable impurities.
4. An alloy for lead acid battery grids as claimed in any of claims 1-3, wherein the lead acid battery grid is of the flooded type.