72 Chapter 7 important consortium of about 70 members whose goal is to enhance and engage with their member organizations in research programs dedicated to advancing lead acid batteries. Nickel Metal-Based Chemistries Another battery chemistry that has received a lot of attention in the 1990s and early 2000s is the nickel-based chemistries, including NiMh and NiCd. These chemistries achieved very high volumes with early portable power applications and subsequently, for NiMh, in HEVs. Nickel-based chemistries offered a higher voltage, higher capacity, and more cycles than traditional lead acid batteries but suffered from several challenges.
Some of the challenges with nickel-based chemistries are the lower voltage and lower energy density compared to lithium-ion and NiMh suffers from “memory effect” that will reduce their available energy over time. The memory effect of these chemistries can be somewhat minimized by conduct- ing periodic full discharges. Nickel-based chemistries also suffer from very high levels of self-discharge ( Table 3 ). Table 3:
Nickel-based chemistries Nickel Metal Hydride Nickel Cadmium Nickel Zinc Nickel Hydrogen Chemistry NiMh NiCd NiZn NiH 2 descriptor Specific energy 30–80 40–60 70–110 50–65 (Wh/kg) Energy density 140–300 50–150 130–350 55–110 (Wh/L) Specific power 250–1000 150 280–2500 – (W/kg) Power density 400 210 420–7000 – (W/L) Nominal voltage 1.2 1.2 1.6 1.4 (per cell) (V) Cycle life 500–1500 1000–2000 300–900 >2000 Self-discharge 30% 20% 20% – (% per month) Operating −20 to +60 −40 to +60 −20 to +50 – temperature range (°C) Applications Automotive hybrid Consumer electronics, Power tools, lawn Satellite applica- electric vehicle power tools, light rail and garden tools, tions:
Low earth (HEV) and train, uninterrupt- light electric orbit and ible power supplies, vehicles, HEVs geosynchronous emergency lighting, earth orbit telecom