Energy_Storage_Technologies.pdf

Starting lighting and ignition sli this design is the

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- Starting, Lighting, and Ignition (SLI): This design is the cheapest, most common type of lead-acid battery, which has very low cycle life at deep cycles. At expected usage conditions, lifetime is 5-7 years [2]. - Deep Cycle : This design has electrode plates that are thicker and sturdier than SLI designs which makes them capable of more frequent deep discharges. At rated usage conditions this design’s lifetime is estimated at 3-5 years [2]. - Stationary : Stationary lead acid batteries are designed to experience only occasional discharges while remain- ing under float-charge for long periods of time. These units, at rated usage conditions, have lifetimes ranging from 15 to 30 years, and some units may have lifetimes of 30 to 40 years [2]. Sealed (SLA) and Valve-regulated (VRLA) : These designs contain the minimal amount of electrolyte required for proper operation, which is why they are often referred to as “starved-electrolyte”. These designs also have more negative electrode active material than positive electrode active material, which helps to promote the recombination of oxygen gas produced during overcharge or float charging. Because of this feature, there is no need to replace the electrolyte (add distilled water), so these designs are essentially maintenance-free. The difference between whether a design is SLA or VRLA is based on the assembly of the electrode plates. The SLA design has plates spirally wound in a cylindrical container, while VRLA has flat plates with a prismatic container. VRLA designs are designed to vent at lower temperatures than SLA designs [1]. This type of battery has a potential lifetime of 10 to 20 years [2]. - Absorbed Glass Mat (AGM): The electrolyte is prevented from moving by being absorbed into a porous microfiber glass mat. Since the electrolyte is immobilized, it can be used in applications where it will be jostled and/or placed in non-upright positions without spilling [1]. - Gelled electrolyte : A chemical is added to the electrolyte to cause it to form a gel, which acts to immobilize it, with similar benefits as the AGM design [1]. System Design Considerations Since lead acid batteries are typically available in predetermined sizes, in larger energy storage systems they are typically connected in series/parallel combinations to get the desired power and energy capacity. In theory, they could be interconnected up to any size, but because interconnecting so many units leads to additional points of potential failure, experience suggest the unit should have a voltage no higher than 2000V. The batteries are typically placed on racks with bus interconnections, and require an HVAC system to maintain the temperature in the proper regime [2]. Additionally hydrogen sensors are installed due to the potential for electrolysis in the battery that can lead to the presence of hydrogen gas.
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