Internet of Things: Batteries A Short Review

1. NETW 1010 Internet of Things: Batteries A Short Review Dr. Eng. Amr T. Abdel-Hamid Fall 2013

2. Eradio Calculations Eradio = (P(per Bit)* Number of Bits)+ (I sleep* V * T) Total Energy used for this module What kind of a battery needed then?!

3. Battery (Short Review) Two cells A real battery Another battery More precisely Duracell batteries 9v battery 6v dry cell

4. Batteries • Cheap • Easy to use • Rechargeable batteries available • Lithium Ion batteries with high capacity • Charging is simple and easy • Size of batteries is a problem • AA battery defines the size of many devices • Environment (temperature) has influence on the capacity

5. Battery Characteristics • Size • Physical: button, AAA, AA, C, D, ... • Energy density (watts per gram or cm3) • Longevity • Capacity (Ah, for drain of C/10 at 20°C) • Number of recharge cycles • Discharge characteristics (voltage drop)

6. Further Characteristics • Cost • Behavioral factors • Temperature range (storage, operation) • Self discharge • Memory effect • Environmental factors • Leakage, gassing, toxicity • Shock resistance

7. Battery Organization

8. Battery Connections

9. Primary (Disposable) Batteries • Zinc carbon (flashlights, toys) • Heavy duty zinc chloride (radios, recorders) • Alkaline (all of the above) • Lithium (photoflash) • Silver, mercury oxide (hearing aid, watches) • Zinc air

10. Alkaline Battery Discharge

11. Secondary (Rechargeable) Batteries • Nickel cadmium • Nickel metal hydride • Alkaline • Lithium ion • Lithium ion polymer • Lead acid

12. Nickel Cadmium Batteries • Chemistry Cadmium (-), nickel hydroxide (+) Potassium hydroxide aqueous electrolyte • Features • Rugged, long life, economical • Good high discharge rate (for power tools) • Relatively low energy density • Toxic

13. NiCd Recharging • Over 1000 cycles (if properly maintained) • Fast, simple charge (even after long storage) C/3 to 4C with temperature monitoring • Self discharge 10% in first day, then 10%/mo Trickle charge (C/16) will maintain charge • Memory effect (Medium Effect over time)

14. NiCd Memory Effect

15. NiMH Battery Discharge

16. NiMH Recharging • Less prone to memory than NiCd • Shallow discharge better than deep Degrades after 200-300 deep cycles Need regular full discharge to avoid crystals • Self discharge 1.5-2.0 more than NiCd • Longer charge time than for NiCd To avoid overheating

17. NiCd v NiMH Self-Discharge

18. Secondary Alkaline Batteries • Features • 50 cycles at 50% discharge • No memory effect • Shallow discharge better than deeper

19. NiCd v Alkaline Discharge

20. Lithium Ion Batteries • Chemistry Graphite (-), cobalt or manganese (+) Nonaqueous electrolyte • Features • 40% more capacity than NiCd • Flat discharge (like NiCd) • Self-discharge 50% less than NiCd • Expensive

21. Lithium Ion Recharging • 300 cycles • 50% capacity at 500 cycles

22. Lithium Ion Polymer Batteries • Chemistry Graphite (-), cobalt or manganese (+) Nonaqueous electrolyte • Features • Slim geometry, flexible shape, light weight • Potentially lower cost (but currently expensive) • Higher discharge • Lower energy density, fewer cycles than Li-ion

23. Battery Capacity

24. Discharge Rates

25. Recharging

26. Energy harvesting •  Capacity of battery limits the lifetime of the device • Battery depletion -> Device cannot work -> (Sensor) network cannot work • Idea: recharge the batteries during operation • Use energy from the environment • Current approaches • Photovoltaics: Solar modules for sensor nodes • Thermoelectric generators • Conversion of temperature differences to energy • Kinetic energy conversion • Piezo-electric principle already tested for shoes • MEMS gas turbines • Convert air- or fluid streams