Batteries for Residential Projects Lead-Acid Technology

Team Members Ajay Renganathan Aakash Bhansali Date Of Presentation- 10/08/2015

Construction of a Battery Lead plates form electrodes. Deep cycle/solar Lead batteries have thicker plates. Acid acts as the electrolytes (ex: H2SO4). Deep cycle/solar Lead batteries replace acid with gelled substances or glass mats Separators are used to obstruct flow of ions directly between plates. Rubber is a favored option The plates are soldered to metal contacts Battery is protected with plastic covering

Technology of lead-acid Batteries Elements of a Battery Discharging- The electron is generated as result of the chemical reaction and thus current is generated. Reaction at the negative electrode is as follows. Pb(s) + HSO−4(aq) → PbSO4(s) + H(aq) + 2e− The reaction on the positive plate during discharge is as follows PbO2(s) + HSO−4(aq) + 3H+(aq) + 2e− → PbSO4(s) + 2H2O(l) Charging stages- 1.Bulk Charge- Responsible for most of the charging with constant current for a long period 2. Topping Charge- Charges the battery with low current till saturation is achieved 3. Float Charge- Covers up for self-discharging

Power and Energy Density

Power and Energy density Lowest power and energy density Therefore, heaviest and largest in size

Types of Batteries Flooded Batteries-  Needs water to be added to the electrolyte for regular charging.  Low initial cost but high maintenance.  More life cycles  Physical limitations  Difficult to transport Picture Courtesy:

Types of Batteries VRLA Batteries  Sealed Batteries, thus water does not need to be changed  Valve allows excess gas to escape automatically.  Shorter Lifespan  Low Maintenance Two types of VRLA batteries:  Absorbed Glass Mat (AGM)  Gel or Tubular Gel

Types of Batteries Absorbed Glass Mat (AGM) Batteries  High charge and Discharge Currents  Better performance over extreme temperatures  Offers flexible charging patterns  Shorter life cycle Picture Courtesy:

Types Of Batteries Gel or Tubular Gel Batteries  Offers Deep Discharge  Longer Life Cycle  Higher Initial cost  Affected by extreme temperature  Cannot be charged flexibly Picture Courtesy:

SWOT Analysis Strengths:  Recyclable- almost 100% recycling in USA  Lower Maintenance Requirements  Lowest self-discharge Weaknesses:  Sulfation- reduces life cycle  Thicker pates make them heavy  Low energy density (30-50 W/kg)  Low Life cycles - ( recharge cycles)  Releases green house gases

SWOT Analysis Opportunities  Low cost factor plays important role  Smart Grid technologies would require Lead-Acid Batteries  Lead Acid Battery market to grow by 3.5% from AGM battery is a key to this growth  Trojan has developed a new AGM battery with greater life cycle Threats:  Li-ion batteries have higher energy density and are lighter. But more expensive  Ni-Cd batteries have longer life cycles, gives more charge current but suffers from significant self-discharging  NiMh batteries have long life cycle and shorter charge period. But need more maintenance and suffer from self-discharging

Conclusion Lead Acid batteries are used in the PV market along with automobile and other sectors due to their low initial costs. Also they are favored as they can be recycled They have a low energy density and are heavy From our analysis: Pricing: flooded< AGM < Gel The battery bank size and price depends on the load it is expected to support

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