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1. HRD CLASS ON BATTERY

2. CONTENTS I. APPLICATION II. BASIC CONSTRUCTION III. TYPES OF BATTERIES IV. WORKING PRINCIPLE V. RATING/ SPECIFICATIONS

3. I. APPLICATION Store Direct Current Electrical Energy in chemical form for later use: at night, and cloudy periods………….in PV system Serve as portable power source for appliances Provide necessary amounts of Surge Power ( e.g : required 3 times or more than the nominal power to start motors, in PV system) Provide stable level of Voltage & Current

4. III. TYPES OF BATTERIES Primarily, two types of batteries: Primary (Non-rechargeable) Secondary (Rechargeable): Deep Discharge: up to 80% DOD Shallow Discharge: w/c gives large current for a short duration; to start a motor Lead Acid: Liquid Vented/ Liquid Electrolyte VRLA/ Sealed Batteries 1. Liquid Vented Made of + ve & - ve plates, lead/ lead alloy placed in an electrolyte solution of Sulphuric acid & water 2. Sealed/ VRLA: No access to electrolytic solution & is valve regulated to exit excess gas generation Also called “Maintenance Free” batteries Generally are of two types: Gel Cell & AGM

5. Gel Cell: The electrolyte is gelled by addition of Silica gel. Advantageous; the gelled electrolyte can’t be spilled; even when broken/ cracked Cost more per unit of capacity compared to Liquid Lead Acid Susceptible to damage from over-charging especially in hot climates Most sealed batteries must be charged to lower voltages & at a lower current rate to prevent excess gas generation AGM (Absorbed Glass Mat): Use Fibrous Silica glass mat to suspend the electrolyte This mat provides pockets that assist in the re-combination of gases generated during charging & limit the amount of Hydrogen-gas produced SPECIAL APPLICATION BATTERIES Ni-Cd/ Ni-Iron: Electrolytic solution is Potassium Hydroxide Recommended for commercial/ Industrial applications in extreme cold temperature (-45 °c or less) Li-Ion : upto 100% DOD, and Longer life batteries; with proper Installation taken into account

6. V. RATING/ SPECIFICATIONS Battery Capacity: Given in AH/ mAH ( in case of small portable devices). E.g : 200AH/ 20Hr Parallel connection: Current capacity adds & voltage is constant. E.g : 2 batteries of 100/ 12V in parallel gives 200AH/ 12V together Series connection: Voltage adds & current capacity is constant. E.g : 2 batteries of 100/ 12V in series gives 100AH/ 24V together AH is not exact measure of battery capacity; is rather an approximation, influenced by: Rate of discharge DOD Temperature Age & condition of battery Depth of Discharge (DOD): Percentage of battery capacity that is withdrawn/ used Commonly takes any number between 20% - 80 %; 50% DOD being the most healthy one Life expectancy/ Cycle: Usually given in Number of Cycles/ years Environmental Conditions: Working temperature (surrounding temperature) Battery capacity will decrease at lower temperature & Increase at higher temperature Generally, 50% loss in battery life for every 15 degrees increase in temperature