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NORMILIZATION AND CONDITIONING OF NICKEL METAL HYDRRIDE BATTERIES. By Chris Harrison. INTRODUCTION. • Charging is the way to restore energy back into batteries that are “empty”. • Rechargeable batteries are important because they can be reused.
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NORMILIZATION AND CONDITIONING OF NICKEL METAL HYDRRIDE BATTERIES By Chris Harrison
INTRODUCTION • Charging is the way to restore energy back into batteries that are “empty”. • Rechargeable batteries are important because they can be reused. • Batteries can be charged in many ways to produce certain results. - Charge #1 fast charges batteries for electric vehicles applications.- Charge #2 recovers batteries that have been unused for an extended period of time. •Charges affect many important battery aspects:- Battery Life - Battery Capacity - Battery Performance
BATTERY EFFECTS • Internal Battery Resistance - As the battery gets increasingly “full”, it becomes harder to squeeze in the remaining energy. • Self Discharge - Batteries naturally decrease in energy as chemicals slowly react inside the battery. SIMPLE CHARGE TYPES • Constant Current- Charges at a certain current for a specified time.- As internal battery resistance increases and current does not drop, temperature can increase. This may damage the battery and be a safety hazard. • Trickle Charge- Same as constant current, but uses very low currents. - Low current allow “full” batteries resist further charging while empty batteries “catch up”.
CHARGE TERMINATION TYPES • Time • Voltage • Temperature and ∆Temperature • ∆Voltage FACTORS EFFECTED BY CHARGING • Charging Efficiency• Charging time • Battery Life • Battery Capacity • Battery Performance
EXAMPLES EXAMPLE PROFILE 1: Begins charge with a high initial current and then drops to a lower current. POSSIBLE RESULT: May produce good charge time, but reduces battery performance. EXAMPLE PROFILE 1: Begins charging with a low current then rises to a high current. POSSIBLE RESULT: May have poor charge efficiency and damages battery because of extreme heat and reduces battery capacity.
REVIEW OF THE LITERATURE • Maintenance-Free Batteries, 2nd Edition, D. Berndt, Research Studies Press Ltd., Somerset, 1997. •The Fifteenth Annual Battery Conference on Applications and Advances (Proceedings), California State University, Long Beach, Jan 11-14, 2000. Improved Charge Algorithms for Valve Regulated Lead-Acid Batteries, E Sexton Et Al. Page 211. • John Rivera (Technician) and Jon Marshall (Engineering Group Leader), Curtis Instruments, Inc. Mount Kisco, NY.
METHODS 1 - Determine how many Amp Hours to charge or discharge from the battery / battery pack 2 - Calculate time and current for charge 3 - Determine what charge would be best to normalize batteries 4 - Determine termination type 4 - Insert batteries into holder 5 - Set up apparatus for desired parameters 6 - Start monitoring charge statistics (e.g. current, voltage) 7 - Start charge 8 - Analyze end float voltages, and prepare for next charge or discharge based of collected data
FUTURE RESEARCH CHARGING CURRENT VS. TEMPERATURE• Intense Charging - More current flows through wires and battery - Generates lots of heat - Could damage the fragile internal materials PRESENT TECHNOLOGY• Terminates when: - Threshold temperature is reached - Temperature change reaches a certain slope, • This allows the battery to cool • Resumes the charge until it reaches that temperature again. • These pauses waste time. • Stop-and-go charging could damage the battery. FUTURE RESEARCH- Temperature regulated charge algorithms