On the Low Temperature Performance of Nickel-Metal Hydride (NiMH) Batteries

Nickel-metal hydride (NiMH) batteries are still major battery systems that are commercially used for hybrid electric vehicle (HEV) applications. This is because they are characterized by long durability, safe operation and significantly lower manufacturing cost, as compared to lithium-ion devices, their major competitor for these applications. However, electrochemical performance of NiMH batteries is strongly dependent on the temperature that they are exposed to. Thus, at temperatures below ca.-20 o C, the capacity of nickel-metal hydride batteries significantly declines (as compared to that recorded at room temperature), primarily due to electrochemical deterioration at their negative (MH) electrodes. This work essentially reports on the electrochemical, low-temperature discharge characteristics of a commercial 6.5 Ah/7.2 V NiMH battery module (used for HEV applications), in comparison to those of advanced, AA size NiMH cells