Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-12-02
2001-07-24
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S247000, C429S248000, C429S251000, C429S252000, C429S129000, C429S131000, C429S132000, C429S133000, C429S134000, C429S135000, C429S163000, C429S161000
Reexamination Certificate
active
06265108
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to valve regulated lead-acid batteries, and more particularly to a battery having a flooded electrolyte condition with improved battery life.
BACKGROUND OF THE INVENTION
Based on the quantity of acid present in a battery, lead-acid batteries are classified as either flooded or starved electrolyte batteries. In flooded batteries, acid is in excess which is also referred to as free acid. Whereas, in starved electrolyte batteries there is no excess or free acid. Starved batteries are designed such that all the acid in the battery is immobilized in the plates and in either the separators or in gel form. Where the acid is immobilized in the separators, the battery is referred to as an absorbed glass matrix (AGM) battery. Where the acid is immobilized in the gel form, the battery is referred to as a gel type battery.
A valve regulated lead-acid (VRLA) battery is a starved electrolyte AGM type battery and has a safety valve which prevents excessive build up of gas pressure inside the battery. A key for the successful operation of a VRLA battery is the oxygen recombination reaction which prevents the water loss from a battery by recombining the oxygen and by suppressing hydrogen gas liberation at the negative electrode. The starved acid design of the battery facilitates the oxygen recombination reaction. The recombination reactions are facilitated by the starved acid or electrolyte condition where the electrolyte is immobilized in glass separators disposed between the plates of the battery.
VRLA batteries have numerous advantages over their counterpart flooded batteries, such as, for example, low maintenance, ease of handling, and high power density. However, deficiencies in VRLA batteries include: a) recombination reactions tend to generate excessive heat and accelerate thermal runaway processes; b) under uncontrolled environments, VRLA batteries dry out since the batteries have a limited amount of electrolyte; c) low heat dissipation; and d) self discharge of the negative electrode leads to premature capacity loss and battery failure. These deficiencies are unique to VRLA batteries.
A need has thus arisen for an improved VRLA battery designed for longer life.
SUMMARY OF THE INVENTION
In accordance with the present invention, a valve regulated lead-acid battery having a plurality of negative and positive electrode plates and a plurality of separators interleave between the plates is provided. A negative strap and positive strap interconnect the respective plurality of negative and positive electrodes. Material soaked with electrolyte is disposed adjacent to the negative strap to thereby increase oxygen reduction.
In accordance with the present invention, a VRLA battery has electrolyte in a flooded state, the electrodes and the separators being fully submerged in the electrolyte. This condition disturbs the “starved” state and minimizes the oxygen recombination reaction. In order for oxygen recombination to occur, the negative strap is wrapped with separator material which is in contact with electrolyte, to constantly moisten the separator material to facilitate the oxygen recombination reaction.
REFERENCES:
patent: 2831127A (1979-01-01), None
patent: 63108667A (1988-05-01), None
Brouillette Gabrielle
Locke Liddell & Sapp LLP
Martin Angela J.
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